pharmacology opto Flashcards

Question

Topamax® can lead to glaucoma via which of the following mechanisms? Iris mydriasis, leading to angle-closure Release of vascular endothelial growth factor, leading to neovascular glaucoma Increased choroidal effusion Decreased pore size of the corneoscleral meshwork

Answer 1

Increased choroidal effusion Topamax® is a drug that is commonly used as an anti-seizure medication but may also be used in the management of migraines, depression, and bipolar disorder as well as to promote weight loss. Use of this drug can cause uveal effusions, leading to swelling of the ciliary body and narrowing of the angle (forward displacement of the lens-iris diaphragm) and leading to myopia and angle-closure glaucoma. Patients who report blurred vision with the use of Topamax® should immediately discontinue the medication due to the increased risk of developing angle-closure glaucoma. Signs and symptoms typically occur 3-14 days after the initiation of treatment.

Answer 2

Balanced salt solution (BSS) himerosal and BAK are microbial agents and can be used in small doses as preservatives on extraocular surfaces; however, if used intraocularly they will result in iritis, cataract formation, and death of corneal endothelial cells. Saline is not an acceptable intraocular irrigating solution because it does not contain the electrolytes needed to maintain proper isotonicity of the corneal endothelium (such as calcium, magnesium, glucose, sodium, potassium, etc.); this will result in swelling and lysis of the endothelial cells. BSS is frequently used for short-term intraocular surgeries as it is isotonic to ocular tissue and contains electrolytes that are needed for normal cell functions.

Answer 3

Vitamin B2 Vitamin B2 is also known as riboflavin. Riboflavin is important for the metabolism of nutrients. Because it is yellow or yellow/orange in color, riboflavin is frequency used to color foods. A deficiency (although quite rare) of vitamin B2 can lead to several ocular complications such as photophobia, corneal neovascularization and keratoconjunctivitis sicca. Dry, cracked lips, ulcers of the mouth, and sore throat may also be experienced. Some studies have reported that vitamin B2 supplementation may decrease the risk of cataracts.

Answer 4

Augmentin® Augmentin® is resistant to beta-lactamase because it is comprised of amoxicillin and clavulanic acid, a compound that inhibits the enzyme beta-lactamase. Clavulanic acid deactivates the enzyme, thereby preserving the beta-lactam ring of the penicillin and allowing it to maintain its effectiveness in destroying the targeted bacteria.

Answer 5

Bimatoprost (Lumigan®) lumigan® is classified as a prostaglandin. This category of glaucoma medications can cause growth of eyelashes as a side effect along with pseudodendrites, photophobia, irritation, superficial punctate keratitis, cystoid macular edema, hyperemia and changes to iris color. By taking advantage of this desired cosmetic side effect, Latisse®, patented by Allergan, was created specifically for the purpose of promoting eyelash length and thickness.

Answer 6

Dexamethasone Prolonged use of steroids both systemically and topically have been linked to an increase in intraocular pressure (IOP). The mechanism by which this occurs is most likely due to a decrease in the facility of aqueous outflow. Of the steroids mentioned, dexamethasone has the greatest tendency to result in increased IOP. Loteprednol is a steroid that minimally affects IOP and therefore should be used in cases where one is concerned about a potentially damaging rise in IOP.

Answer 7

Anterior uveitis Amblyopia Posterior synechiae Atropine is a parasympatholytic drug. Administration of atropine may result in glaucoma in narrow-angle patients because it causes pupil dilation that leads to blockage of the trabecular meshwork, causing a spike in intraocular pressure. Because atropine causes cycloplegia, it can be used in the management of amblyopia, as it forces the child to utilize their weaker eye, hopefully serving to strengthen and increase the visual acuity of that eye. Due to the fact that atropine results in pupil dilation, it is often used in the treatment of anterior uveitis to help prevent formation or promote breakdown of synechiae. It also aids in pain management by controlling pupil size and avoiding unnecessary movement of the iris muscles, which can be very painful in this inflammatory condition.

Answer 8

Pilocarpine Pilocarpine should not be prescribed to this patient for several reasons. First, he is young and pilocarpine should not be prescribed to patients less than 40 years old as it can increase the risk of early cataract formation. Secondly, he has a history of a retinal detachment; pilocarpine use increases the likelihood of retinal detachment. All of the other choices would be suitable; however, it is best to start with a prostaglandin as this class of anti-glaucoma medication generally results in good compliance since it needs to be administered once daily; it also leads to excellent intraocular pressure stability. Other reasons not to prescribe pilocarpine as a primary glaucoma treatment include the fact that it can create a brow ache, cause an increase in myopia and it constricts the pupil thereby reducing acuity under low light levels.

Answer 9

The primary absorption pathway for small, lipophilic drugs is the transcorneal route The primary absorption pathway for large, hydrophilic drugs is the transconjunctival route Topical instillation of medications is the most common method utilized to administer treatment for ocular conditions. There are two major pathways that allow an ophthalmic drug to enter the eye: the transcorneal route and the transconjunctival (conjunctiva-sclera-ciliary body) route. Various properties of the topical drugs will determine which pathway is used to permeate the ocular tissue barriers. The primary absorption route for small, lipophilic drugs is the transcorneal route, while the primary pathway for larger, hydrophilic drugs is the transconjunctival route.

Answer 10

Vitamin C Vitamin C, also known as ascorbic acid, is a powerful antioxidant. Vitamin C facilitates the absorption of dietary iron. It is also a cofactor in many enzymatic reactions, including the synthesis of collagen. Avitaminosis C results in scurvy caused by the creation of unstable collagen. Scurvy presents with general weakness, anemia, brown spots on the skin, spongy gums, petechial hemorrhages of the skin and mucous membranes, proptosis and feelings of paralysis, amongst other symptoms. Advanced cases are remarkable for open suppurative wounds, loss of teeth, and death. Interesting fact: Broccoli contains more vitamin C than oranges, 90mg/100mg vs. 50mg/100mg. The kakadu plum contains a whopping 3100mg/100mg of vitamin C!! Severe alcoholics can become victims of scurvy due to malnutrition.

Answer 11

Lotemax® (0.5% loteprednol) Lotemax® would be the best choice to provide immediate relief. Alrex® is a mild steroid that is frequently prescribed for seasonal allergic conjunctivitis; it is generally prescribed in conjunction with either a mast cell stabilizer or a dual-acting antihistamine such as Patanol®. However, in this case, because the patient is extremely symptomatic and a high degree of chemosis is present, it is best to go with a slightly stronger steroid such as Lotemax® rather than Alrex®. Steroids are used transiently and serve to give immediate relief from pruritus and edema, while the mast cell stabilizer helps to prevent further exacerbation for a longer time frame. Cromolyn sodium and Alomide® are mast cell stabilizers and are useful for chronic allergic reactions rather than acute ones. Upon initiation of treatment, mast cell stabilizers frequently have a lag time before resolution of symptoms and are therefore sometimes started prior to allergy season to ensure maximum therapeutic effect. 1% tropicamide will cause dilation of the eye but will not resolve any of her symptoms.

Answer 12

1% Atropine Atropine is a useful ophthalmic drop that is available in 0.5%, 1% and 2% concentrations. Its cycloplegic effect can last for as long as 12 days. It is commonly utilized for cycloplegic refractions in children, treatment of uveitis, amblyopia, and to test for glaucoma by inducing acute angle-closure glaucoma (verifies if angles are open). Its ocular side effects include irritation, contact dermatitis, elevation of intraocular pressure (IOP), and angle-closure glaucoma. Atropine is contraindicated in people who have narrow angle glaucoma and open angle glaucoma because it can cause an increase in IOP. Atropine should also not be used in children with Down's syndrome because it leads to a hyper-sensitive reaction where the extent of the mydriasis is greater than that of normals. Although some articles currently exist that refute the argument that atropine is not safe to use in people with Down's syndrome, it is ALWAYS best to exercise caution in the best interests of the patient. There are many other cycloplegic agents that can be used as alternatives without posing a risk to patients with Trisomy 21. Bear in mind that homatropine and scopolamine carry the same contraindications as atropine.

Answer 13

Elevated levels of low-density lipoproteins and triglycerides are associated with increased risk of heart disease and stroke because they can lead to plaque formation and build-up on the inside of arteries, which narrows the lumen of the blood vessels. HDLs aid in decreasing the risk of cardiovascular disease; therefore, elevated levels of this type of cholesterol are desirable. HMG-CoA reductase is the enzyme found in the mevalonate pathway, which is responsible for the synthesis of cholesterol. Drugs that inhibit HMG-CoA reductase decrease the concentration of cholesterol in hepatic cells, which results in an increase in the synthesis of hepatic receptors for LDL. This in turn causes decreased levels of plasma LDL, thereby resulting in an increase in plasma HDL levels.

Answer 14

Pseudoephedrine Pseudoephedrine is an adrenergic agonist; therefore, it is important to exercise caution when used in patients who suffer from cardiovascular disease. Pseudoephedrine acts as a decongestant by causing constriction of blood vessels, leading to decreased mucous production and a clearing of the nasal passage. Fexofenadine (Allegra®), desloratadine (Clarinex®), and diphenhydramine (Benadryl®) are all oral antihistamines.

Answer 15

Acetaminophen and hydrocodone Vicodin® is comprised of acetaminophen (500mg) and hydrocodone (5 mg). Other common trade names include Percocet®, Percodan®, and Lortab®. Percocet® is a combination of acetaminophen (120mg) and oxycodone (5 mg). Percodan® is a combination of aspirin (325 mg) and oxycodone HCL (4.5 mg). Lortab® is a blend of hydrocodone (2.5 mg) and acetaminophen (120mg).

Answer 16

Category X Category X pertains to a drug that has been ruled dangerous to a developing fetus and is contraindicated in pregnancy. Category A refers to a drug that in controlled studies did not pose a risk to the child during pregnancy. Category B drugs do not display evidence of risk in humans. Category C denotes safety for use of the drug has not been established and the drug is to be used only if absolutely necessary when benefits outweigh the risks. Category D drugs positively denote evidence of risk. Category Z does not exist.

Answer 17

Gastrointestinal upset Many patients who take erythromycin experience GI upset; it is advised that this medicine be taken either 1 hour before or two hours after a meal. Erythromycin has not been known to cause weight gain or tinnitus, nor has erythromycin been linked to otitis media. It is noteworthy that aspirin use has been associated with tinnitus.

Answer 18

Avoid signs and symptoms of rebound ocular inflammation When prescribing a topical ocular corticosteroid, the tapering schedule of the medication is just as important as the initial dose. It is imperative not to prematurely discontinue steroid medications and to closely monitor the patient for signs of rebound inflammation during and after the tapering process. The mechanism for developing rebound inflammation stems from the fact that prolonged use of corticosteroids causes a reduction in the amount of mature circulating leukocytic elements. If the steroid is stopped abruptly, the immature cells can proliferate, producing large quantities of antibodies in response to the residual antigen remaining in the tissue. This physiologic action is what causes rebound inflammation. The exaggerated inflammatory response is more commonly associated with systemic steroid use, but prolonged topical ocular therapy (usually longer than 1 month) can also induce this response. A typical steroid taper should begin once the inflammation is completely controlled. There are many different tapering schedules that may be implemented depending on the patient's condition, but classically, the dose of the steroid should be halved for each given time interval. For example, if you prescribed a steroid q.i.d. x 5 days, you could taper to b.i.d. x 5 days, then q.day x 5 days. The longer the treatment period or more frequent the dosage, the longer the taper will be. With long-term oral corticosteroid use, there is a risk of developing adrenal insufficiency if the steroid is not tapered properly. This is due to the fact that the adrenal glands decrease their normal production of natural cortisol when an individual is taking a dose of steroids. Tapering the steroid is important such that the adrenal glands can return to producing habitual levels of cortisol before complete cessation of the oral steroids.

Answer 19

The organism is sensitive to the normal dose of moxifloxacin Results of antimicrobial sensitivity testing are typically reported for each drug as follows: - Susceptible: the organism is sensitive to the normal dosage of the tested antimicrobial agent - Intermediate: the organism is likely sensitive to a higher-than-normal dose of the tested antimicrobial agent - Resistant: the organism is not sensitive to the tested dose of the antimicrobial agent

Answer 20

Ocular symptoms everal studies have shown that intranasal corticosteroids improve ocular allergy symptom scores. The hypothesized mechanism is based on the inhibition of the nasal-ocular reflex. Other proposed mechanisms include retrograde diffusion through the nasolacrimal duct and systemic absorption of the corticosteroid

Answer 21

Phenylephrine The mydriatic drop with the shortest duration is phenylephrine, which typically lasts about 3 hours (and has no cycloplegic effect). - Tropicamide has an effective duration of 6 hours - Cyclopentolate lasts for about 24 hours - Homatropine has a mydriatic effect lasting for up to 2 days - Atropine is the most powerful mydriatic and cycloplegic, lasting up to 2 weeks

Answer 22

Tetracyclines inhibit bacterial lipase production, thereby reducing the concentration of deleterious free fatty acids etracyclines are commonly used in the treatment of chronic posterior blepharitis due to their ability to inhibit bacterial lipase production, which in turn reduces the concentration of free fatty acids that cause inflammation and irritation to the eyelids. Tetracyclines also result in decreased concentration of bacteria on the eyelids, but this drug is not bactericidal. Restasis® is a medicated eye drop that is occasionally used in the treatment of dry eye associated with posterior blepharitis. Its mechanism of action involves inhibiting the activation of T-cells, which normally lead to inflammation and decreased tear production. Omega-3 fatty acids (fish oil) are also very commonly used in management of posterior blepharitis due to their effects on modulating synthesis of both inflammatory and anti-inflammatory prostaglandins.

Answer 23

Ibuprofen Aspirin Heparin Warfarin Folic acid is a water-soluble B vitamin complex needed by the body to manufacture red blood cells, which can be used to help treat megaloblastic anemia. Folic acid does not affect clotting of blood. Heparin and Warfarin accelerate the inhibition of factor Xa by binding to and potentiating antithrombin III. Factor Xa is a key enzyme in the coagulation cascade; therefore, inhibition of this enzyme aids in the prevention of thrombosis. Aspirin, and to a lesser degree ibuprofen, inhibit the synthesis of thromboxin A2 (TXA2), which works in conjunction with ADP to bring about platelet adhesion. Decreasing TXA2 serves to prevent thrombosis. Oral contraceptives have been associated with an increased risk of blood clot formation.

Answer 24

Erythromycin ointment Erythromycin is a good antibacterial ointment for Gram-positive organisms. It works well for chronic, mild inflammatory cases of blepharitis and has very low potential for toxic and allergic reactions. Other good options would be Polysporin®, Bacitracin, gentamicin, or tobramycin ophthalmic ointments. Petrolatum ointment is good for excessive dryness but would combat neither the bacteria nor the inflammation. Pred Forte® would work well for the inflammatory component but would not help to resolve the infective portion. A good alternative for moderate to severe cases of blepharitis where lid scrubs might be too painful would be topical antibiotic-steroid combinations such as TobraDex®. Artificial tears are always good to keep the eye flushed and clean, but they must be used in conjunction with other regimens.

Answer 25

Bactrim® Bactrim® is a combination of trimethoprim and sulfamethoxazole and therefore is contraindicated. All of the other drugs listed here are sulfa-free. You will be expected to have general knowledge of commonly prescribed drugs.

Answer 26

Gentamicin Although all of the drops mentioned, if administered for a prolonged period, will cause a hypersensitive reaction or delay wound healing, gentamicin displays the greatest affinity for corneal toxicity. Gentamicin can cause punctate epithelial erosions, delayed re-epithelialization, and corneal ulceration. It is generally best to choose a fourth or fifth generation fluoroquinolone to treat infections as they possess good broad-spectrum antibacterial coverage and, when used properly, decrease the chances for resistance as they are fairly good at eradicating the offending bacteria.

Answer 27

Beta-blockers Although rare, a serious complication of fluorescein angiography is anaphylaxis. While beta-blockers (both topical and oral forms) do not directly interfere with sodium fluorescein, should anaphylaxis occur in individuals taking beta-blockers, the allergic reaction is much more difficult to manage due to decreased effectiveness of epinephrine. Caution should always be exercised when performing fluorescein angiography; however, extra precautions do not need to be taken for patients on anti-diabetic medications, blood thinners, or anti-malarials.

Answer 28

Amiodarone Chloroquine CHI T fabry's dis Patients with vortex keratopathy (also known as whorl keratopathy or corneal verticillata) present with whorl-like corneal epithelial deposits that occur as a result of the ingestion of certain systemic medications. These characteristic corneal changes begin as fine greyish or brownish opacities in the inferior corneal epithelium that arborize and create a whorl-like pattern that swirls outward from a point just below the pupil, sparing the limbus. Although deposits typically involve the visual axis, patients do not experience a decrease in visual acuity; however, some may report the presence of haloes around lights. Common medications that cause vortex keratopathy include chloroquine, hydroxychloroquine, and amiodarone. In the case of chloroquine and hydroxychloroquine, there is no relationship between the development of keratopathy and the dosage or duration of treatment. Additionally, virtually all patients on amiodarone will develop corneal changes; however, the severity is associated with longer duration and higher dosage of the medication. Keratopathy is usually reversible on cessation of therapy. Other medications that may cause this corneal finding include indomethacin, tamoxifen and phenothiazines.

Answer 29

Lipid solubility Ophthalmic drops that are comprised of both lipid (non-polar) and water-soluble (polar) components result in the most effective preparation. The tight junctions of the corneal epithelium keep hydrophilic drugs out but allow good penetration for lipid-soluble drugs. In contrast, the corneal stroma demonstrates good penetration for water-soluble agents. However, a HIGHLY polar agent will not cross the corneal epithelium; therefore, a mildly polar substance is advantageous over a highly polar agent. One should NEVER place alcohol on the eye as it will instantly debride the corneal epithelium; ALWAYS rinse all instruments used for ocular procedures with saline solution after sterilization with any agent that could be toxic to the cornea. Solutions with high pH (basic) are more damaging to the cornea than solutions with a lower pH (acidic). It is important to use solutions that are close to a neutral pH (7.0) to eliminate possible damage to the cornea.

Answer 30

Anti-inflammatory; bronchodilator Fluticasone is a synthetic corticosteroid that has a very potent anti-inflammatory action. Inflammation plays an important role in the pathogenesis of asthma; therefore, this anti-inflammatory is very effective in helping to control asthmatic complications. As is the case with all other steroids, patients using Advair® should be examined periodically to monitor intraocular pressure and possible development of cataracts. Salmeterol is a long-acting beta2-adrenergic agonist. Beta2-adrenoceptors are the predominant adrenergic receptors involved in bronchial smooth muscle, with little association to the heart. Salmeterol acts to increase the levels of circulating cyclic AMP in the bloodstream; this causes relaxation of bronchial smooth muscle and inhibition of the release of mediators of immediate hypersensitivity from cells (especially mast cells).

Answer 31

Cromolyn sodium Cromolyn sodium stabilizes mast cells but does not possess the ability to block H-1 receptor sites. Mast cell stabilizers are useful for chronic allergic eye disease but have an associated lag time and therefore do not provide instant relief of symptoms. Stabilization of mast cells results in prevention of inflammatory mediators such as histamine. Patanol® and Zaditor® are classified as dual-acting agents because they block H-1 receptor sites in addition to stabilizing mast cells preventing degranulation. Livostin® is a topical antihistamine that serves solely to block H-1 receptor sites and therefore is effective in suppressing itching, but does not result in long-term relief.

Answer 32

Xalatan® (latanoprost) Xalatan® should not be prescribed because prostaglandins are contraindicated when there is active ocular inflammation. Trusopt®, Timolol® and Alphagan-P® could all be used to decrease her intraocular pressure (IOP) but Alphagan-P® would be the best drop to prescribe. Alphagan-P® is frequently utilized to reduce IOP following anterior segment laser surgery, such as in argon laser trabeculoplasty, which frequently causes transient, mild inflammation. It should be stated that clinically, if the left eye has normal IOP and you see flare due to iritis, this would indicate inflammatory glaucoma which is best treated with a steroid.

Answer 33

Carbonic anhydrase inhibitors Carbonic anhydrase inhibitors (CAIs) are sulfonamide derivatives; therefore, cautions and contraindications against this class of medication in a patient with a known allergy to sulfa are relevant. There are many other options for treatment in patients who cannot take CAIs; however, if other medications are not effective, or are also contraindication, surgical treatment may then be necessary.

Answer 34

Pacerone® (amiodarone) Amiodarone is an anti-arrhythmic medication. Use of this drug commonly causes yellow/brown or white powdery corneal epithelial deposits, located inferocentrally, that appear to swirl outward while sparing the limbus. These deposits minimally affect visual acuity, if at all. The aforementioned deposits can also be observed in Fabry's disease and in patients taking tamoxifen, chlorpromazine, chloroquine and indomethacin.

Answer 35

Loteprednol esearch has demonstrated that ester-based steroids possess the least likelihood of causing a PSC. To date, the only ester-based topical ophthalmic steroid is loteprednol. Loteprednol possesses an ester group in the carbon 20 position rather than a ketone group. Posterior capsular cataract formation occurs as a result of the interaction between the ketone group and lens proteins, causing the formation of a Schiff base intermediate and eventually leading to PSC development. Because loteprednol does not contain a ketone group, the probability of PSC formation is significantly diminished.

Answer 36

Inhibition of T-cell activation While the exact mechanism of action of cyclosporine remains controversial, it is generally accepted that cyclosporine inhibits calcineurin in CD4+ T helper cells which, under normal circumstances, are responsible for production of interleukin-2 (IL-2). IL-2 normally stimulates activation and proliferation of cytotoxic T cells and other helper T cells. Cyclosporine prevents this activation and acts as an anti-inflammatory. One of the major causes of KCS is autoimmune destruction of lacrimal cells by T cells. Therefore, topical cyclosporine can be protective. In all likelihood, there are likely additional mechanisms of action for cyclosporine in the treatment of KCS, but this is one of the most accepted mechanisms and is the best option from the choices given here.

Answer 37

Penicillins From a biochemistry perspective, first-generation cephalosporins and penicillin-based medications appear similar in that their physical pharmacological make-ups both possess a beta-lactam ring. Most studies purport that roughly 10% (although recent studies suggest 1% or less) of patients who are allergic to penicillin may also potentially exhibit an allergic response to the first-generation cephalosporins. The cross-reactivity between penicillins and cephalosporins is almost non-existent with the third-generation cephalosporins. Although the chances of a patient possessing a cross-reactivity between penicillin and cephalosporin drugs is very rare, it is best to prescribe an alternate antibiotic when a known allergy to penicillins exists.

Answer 38

Sloughing of the corneal epithelium Prolonged use of topical anesthetics applied to the cornea causes softening and loosening of the epithelium. Although this property helps to increase absorption of other drugs such as those used for dilation, overuse can cause severe damage. The junctions between the epithelial cells can become disrupted to the point of corneal sloughing, leading to blurred vision or in severe cases, corneal opacification. Studies have shown that corneal softening occurs to a greater extent with tetracaine than with proparacaine. To date there have not been any correlations between proparacaine use and cataracts, miosis, arcus, or Fuch's dystrophy.

Answer 39

Antagonism of beta receptors, causing decreased heart rate and relaxation of vascular tone Beta blockers serve to decrease blood pressure by blocking the effects of catecholamines (such as epinephrine), thereby allowing for diminished cardiac output and decreased peripheral resistance (attributable to vasodilation). A marked reduction in renin released by the kidneys helps to lower blood pressure by decreasing amounts of circulating angiotensin II, which is a powerful vasoconstrictor. Angiotensin-converting enzyme (ACE) converts angiotensin I into angiotensin II; therefore, drugs that inhibit ACE help to lower blood pressure.

Answer 40

Brimonidine Brimonidine (Alphagan®) belongs to the alpha-2 agonist class of glaucoma medications. In addition to its effect of lowering intraocular pressure (IOP), studies have shown that by activating alpha-2 pathways, brimonidine can also enhance neuronal cell survival rates. It is thought that the mechanism by which neuroprotection is provided has to do with upregulation of the expression of an anti-apoptotic gene, which leads to increased survival rates of neurons even after an ischemic event has occurred.

Answer 41

rescula® is classified as a prostaglandin. Prostaglandins decrease intraocular pressure by increasing uveoscleral outflow. Iopidine® is an adrenergic alpha-2 agonist; Betagan® is a beta blocker; Azopt® is categorized as a carbonic anhydrase inhibitor. Note: Prostaglandins generally end in "prost" except for unoprostone (Rescula®).

Answer 42

Erythromycin Erythromycin and azithromycin belong to a class of drugs called macrolides. Macrolides are effective antibiotics because they bind to the 50S subunit of bacterial ribosomes, thus interfering with bacterial protein synthesis. Tetracycline and doxycycline are classified as tetracyclines. This class of drugs also interferes with protein synthesis via binding to the 30S ribosomal subunit. Amoxicillin, Augmentin®, cloxacillin, dicloxacillin are common anti-bacterials belonging to a class of drugs termed penicillins. Penicillins disrupt cell wall synthesis, making them valuable and commonly used antibiotics. Tobramycin, gentamicin and neomycin are categorized as aminoglycosides, which serve as antimicrobials via two mechanisms. Aminoglycosides inhibit bacterial protein synthesis as well as they cause the creation of openings in bacterial cell membranes, allowing for increased antibiotic uptake.

Answer 43

Lipid solubility Endothelial cells that line the walls of the brain's capillaries are joined via tight junctions. These connections form the blood-brain barrier. The tight junctions prevent large molecules and substances from passing through the spaces between cells. Instead, substances must cross through the actual cells themselves. Movement of desirable substances (such as glucose) across the barrier is achieved by carrier proteins found in the walls of the plasma membranes. However, some lipid-soluble agents can diffuse though the lipid bilayer. It is due to this flaw that nicotine, barbiturates, caffeine, heroine, alcohol, and other lipid-soluble drugs can readily pass through the membrane and cause rapid alteration of normal brain function.

Answer 44

Vitamin B1 Vitamin B1 is also known as thiamine. Thiamine is important for carbohydrate metabolism and the maintenance of neuronal tissue. Although rarely seen in the United States due to the fact that most foods are enriched with vitamins, a B1 deficiency can result in beriberi. Symptoms of beriberi include difficulty walking, loss of sensation in hands and feet, paralysis (due to deterioration of myelin sheath), nystagmus, speech difficulty/mental confusion, ophthalmoplegia, and congestive heart failure. Alcoholism can lead to beriberi due to malnutrition. Vitamin B2, also known as riboflavin, aids in the metabolism of nutrients. Avitaminosis B2 can result in decreased visual acuity due to corneal neovascularization, keratoconjunctivitis sicca, or cataract formation. Vitamin B3 (a.k.a. niacin) is responsible for fat and carbohydrate metabolism. A deficiency of Vitamin B3 can cause pellagra, which results in diarrhea, dementia, and dermatitis. Niacin can be used to treat hyperlipoproteinemia. Vitamin B6, also called pyridoxine, serves an important role as a coenzyme for the formation of hemoglobin as well as amino acid and protein metabolism.

Answer 45

Talc Talc retinopathy can occur with IV drug use such as cocaine and heroin. Retinal deposits result from fillers that are added to the drugs. The talc travels through the circulatory system and becomes trapped in the small retinal capillaries. Generally, visual acuity remains unaffected; however, the capillaries can become blocked, leading to areas of non-perfusion. Talc can also deposit in the small blood vessels of the lungs, liver, spleen, kidneys, and lymph nodes. Pulmonary complications may arise from talc deposits such as edema and fibrosis. It is important to ensure pulmonary health; therefore, x-rays of the lungs should be ordered. If retinal ischemia is suspected, fluorescein angiography will confirm areas of vascular leakage or non-perfusion.

Answer 46

Rifampin Rifampin is a medication commonly used in conjunction with other medications to treat tuberculosis. Due to the fact that rifampin is red in color, it can lead to a harmless side effect of a red-orange discoloration of the tears, saliva, sputum, stool, and sweat. Erythromycin, aspirin, and tetracycline can all be excreted in the tears after oral ingestion; however, they do not alter its color. It is advisable for patients who are taking rifampin to discontinue use of contact lenses until the medication is finished as the lenses may become stained.

Answer 47

``` Headache opical antihistamines and mast cell stabilizers such as Patanol® (olopatadine) are commonly prescribed to relieve the symptoms associated with ocular allergies. They are a very effective class of medication due to their dual action mechanisms. Topical antihistamines that possess this dual action are olopatadine (Patanol®), ketotifen fumarate (Zaditor®), azelastine (Optivar®), and epinastine (Elestat®). The aforementioned drops serve to alleviate itching and redness by blocking H1 receptors as well as inhibiting mast cell and basophil degranulation. Side effects of topical antihistamine/mast cell stabilizers include stinging upon instillation, headaches, and adverse taste (don't forget to inform your patients about punctual occlusion!). Tachycardia, depression, gastrointestinal discomfort, and visual hallucinations have not been reported with Patanol® use. ```

Answer 48

Beta-blockers Beta-blockers have a potential to decrease the heart rate. It is important to obtain baseline information for both heart rate and blood pressure to compare during subsequent follow-up with patients using beta-blocker medications. Beta-blockers taken as topical medications for eye-related issues may drain through the nasolacrimal duct and become absorbed by the nasal mucosa entering the blood stream. This process bypasses first pass metabolism and thus parallels obtaining the drug intravenously; this may have a significant effect on the patient's heart rate.

Answer 49

7 year-old Caucasian female Research demonstrates that children, particularly those under the age of 10, exhibit a higher likelihood of intraocular pressure (IOP) increases in response to topical steroid use. In the event that a steroid is required, it is prudent to prescribe an ester-based steroid (such as loteprednol) in order to minimize the chances of a steroid induced increase in IOP.

Answer 50

Doxycycline Doxycycline can be prescribed prophylactically in the event of possible corneal thinning. Doxycycline inhibits collagenase, an enzyme possessed by some organisms used to break down collagen. It is useful for corneal ulcers, chemical burns, disorders related to collagen vascular thinning and so forth. The other antibiotics listed do not have the ability to preserve collagen via inhibition of collagenase.

Answer 51

Class I agent (examples include Dilantin®, lidocaine and quinidine); block fast sodium channels Class I agents affect sodium channels which ultimately serve to either lengthen or shorten the duration of the action potential and help to prevent ventricular arrhythmias. Class II agents decrease sympathetic activity on the heart by blocking beta adrenergic receptors and aid in preventing recurrence of myocardial infarction. Class III agents prolong repolarization by blocking potassium channels, thereby preventing arrhythmias. Class IV agents block calcium channels thereby decreasing conduction through the AV node.

Answer 52

Color vision testing Ethambutol (EMB) is a medication that is commonly used as a treatment for tuberculosis as well as Mycobacterium avium lung disease. Ocular complications include optic and retrobulbar neuritis. Patients may report decreased visual acuity, a color vision deficit, central scotomas, or constriction of visual fields. Bitemporal visual field defects may also occur. Ophthalmoscopic findings are typically unremarkable. It is thought that the small papillo-macular bundle axons are affected in ethambutol toxicity. Because these axons are small, optic atrophy will not be visualized until months after the damage has occurred. Once the medication is discontinued, visual signs and symptoms typically improve, although in rare cases, the deficits may remain permanently. Current protocol recommends that patients on 15mg/kg/day of ethambutol should receive monthly routine check-ups during which visual acuity and color vision are evaluated. However, in the event that all exam findings are unremarkable in a patient taking EMB but the patient reports visual symptoms, the medication should be discontinued. Signs and/or symptoms typically develop 2-5 months after the initiation of therapy. Further investigations are currently underway to determine the effectiveness of OCT on the early detection of ethambutol ocular-related toxicity.

Answer 53

Minocycline oxycycline, tetracycline, and minocycline belong to the tetracycline class of medications. These antibiotics are frequently used in the treatment of acne, meibomian gland dysfunction, and other infections. Although the mechanism as to why intracranial hypertension occurs remains unclear at this time, all of these medications have the potential to cause idiopathic intracranial hypertension (also known as pseudotumor cerebri or PTC). Because minocycline possesses a high lipid solubility, it has a higher affinity to pass into the cerebrospinal fluid, which may lead to benign (idiopathic) intracranial hypertension. Unlike the typical form of PTC, increased intracranial hypertension as a result of "cycline medication" use occurs equally in males and females and does not have a predilection for overweight females of child-bearing age. The time lag for the development of PTC after the initiation of "cycline" therapy remains unclear, as some patients may displays signs after two weeks of taking the medication while others do not report symptoms until a year has passed after the commencement of therapy. Patients on a "cycline" medication who report headaches, diplopia, or present with sixth cranial nerve palsy or swollen optic nerves should cease taking this medication.

Answer 54

Hydrogen Peroxide (H2O2) Hydrogen Peroxide (3%) is a very useful antiseptic and disinfectant. It is also bactericidal and virucidal. Mercurials such as thimerosal are very toxic and only mildly bacteriostatic. Chlorhexidine disrupts the bacterial cell membrane and is useful for the prevention of dental cavities but does not possess virucidal properties. BAK is very commonly used in ophthalmic drop preparations as a preservative. It denatures bacterial cell membranes and therefore, depending on its concentration, can be used as a bacteriostatic agent (low concentrations) or bactericidal or fungicidal agent (high concentrations), but it is not virucidal. It should be noted that the effectiveness of BAK is diminished by soap, blood, and cotton. Because particles of HIV can be found in tears, it is important to disinfect Goldmann tonometer tips. Studies have shown that disinfecting a tonometer tip with 3% H2O2 is effective for HIV and Herpes simplex I and II.

Answer 55

Vitamin D Vitamin D plays a large role in regulating calcium and phosphate levels within the body. A major source of Vitamin D is sunlight; however, UV exposure can increase the risk of skin cancer. UV light converts Vitamin D to its active form, allowing for greater absorption of calcium in the gut. The calcium is then deposited into the bones, teeth etc. Dietary forms of Vitamin D include butter, eggs, margarine, fish liver oil, and fortified milk and juice.

Answer 56

Pred Forte® Pred Forte® is an ocular medication that is in suspension form; therefore, it is important to shake this medication well before use. Other forms of prednisolone that are suspensions include Pred Mild®, Econopred®, and Econopred Plus®. On the other hand, there are prednisolone ocular medications that are solutions, making shaking of the bottle unnecessary. These include AK-Pred®, Inflamase Mild®, and Inflamase Forte®. Zymaxid® is a 4th generation fluoroquinolone antibiotic that is bottled in solution form, as well as Acular®, which is an ocular non-steroidal anti-inflammatory drug (NSAID). FreshKote® is a prescription artificial tear that also does not need to be shaken before use.

Answer 57

Hematoma at the injection site A common complication of sodium fluorescein injection is a hematoma at the injection site and/or extravasation of the fluorescein. Extravasation occurs when the fluorescein is mistakenly injected into the perivascular space instead of the vessel. If this occurs, patients will complain of a burning sensation at the injection site. Due to the pH of sodium fluorescein, extravasation may lead to necrosis of the tissue surrounding the injection site. Common side effects of sodium fluorescein injection include nausea, emesis, urticaria, and anaphylaxis (very rare).

Answer 58

Zyrtec® (cetirizine) Oral H-1 antihistamines have several ocular indications. Common H-1 oral antihistamines include Claritin® (loratidine), Zyrtec® (cetirizine), Allegra® (fexofenadine), Clarinex® (desloratadine), and Benadryl® (diphenhydramine). The oral antihistamines serve to alleviate symptoms associated with a Type I allergic response which can include itching, lid edema, chemosis, and excessive tearing. Oral antihistamines can also be recommended for lid myokymia which, although irritating, is not sight-threatening. It is important to distinguish between first generation and second generation oral antihistamines because first generation oral antihistamines (Benadryl®) cause central nervous system (CNS) depression and drowsiness. The second generation oral antihistamines (Claritin®, Zyrtec®, Allegra®, and Clarinex®) are non-sedating as they do not penetrate the CNS. Voltaren® is an NSAID and will not alter the duration of lid myokymia; neither will prednisolone or bimatoprost (Lumigan®).

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