Flashcards in Drugs Deck (20)
fraction of an administered dose of unchanged drug that reaches systemic circulation and is available for clinical effect
Describe first pass metabolism.
Fraction of a drug lost during the process of absorption in the gut and metabolism in the liver. Concentration of drug is greatly reduced before it reaches systemic circulation.
What are the advantages and disadvantages of administering a drug via the oral route?
Pros = socially acceptable
Cons = first pass metabolism effect reduces amount of drug available in the systemic circulation; risk of drug causing irritation and ulceration (e.g. NSAIDs)
Name examples of CV drugs.
Anti-platelets - aspirin, clopidogrel, dypyramidole
Anti-coagulants - warfarin, rivaroxaban, dabigatran
Calcium channel blockers - nifidepine, amlodipine
Nitrates - glycerol trinitrate (GTN)
Anti-arrythmics i.e. Beta blockers - atenolol, propranolol
Lipid lowering drugs - simvastatin
Diuretics - bendroflumethiazide, frusemide
ACE inhibitors - ramapril, lisinopril
What is the dental relevance of calcium channel blockers?
The drugs acting on peripheral blood vessels (nifedipine, amlodipine) can cause gingival hyperplasia.
What are the advantages and disadvantages of administering a drug via intravenous? Give an example of a drug administered this way.
rapid immediate onset of drug, avoids first pass metabolism, continuous and closely monitored administration
requires IV access - can be painful and difficult to obtain (drug users), increased infection risk
What are the advantages and disadvantages of administering a drug via subcutaneous? Give an example of a drug administered this way.
avoids first pass metabolism, constant slow and prolonged absorption by fatty tissue
needle breaks protective barrier against infection
What are the advantages and disadvantages of administering a drug via intramuscular? Give an example of a drug administered this way.
rapid onset, shorter duration, muscle can absorb liquid better than subcutaneous layer
neurovascular (nerve) damage, bleeding, painful, infection risk, dependent on blood flow - delayed absorption in shock
What are the advantages and disadvantages of administering a drug via transdermal? Give an example of a drug administered this way.
avoids first pass metabolism, controlled and continuous release
skin is an effective barrier - only small molecule medications will work
What are examples of adverse effects of therapeutic steroids (e.g. hydrocortisone, prednisolone)?
hypertension, type II diabetes, osteoporosis, increased infection risk
What is first order kinetics and zero order kinetics in drug clearance? What graphs do these produce? Give two examples of drugs that are eliminated through zero order kinetics.
1st order = drug elimination is by passive diffusion only; produces logarithmic graph
zero order = drug elimination is an active process, produces linear graph
alcohol and paracetemol
Which route of drug administration gives the most predictable bioavailability?
What factors affect oral absorption of drugs?
lipid solubility and ionisation, drug formulation, GI motility, interactions with other substances, GI tract disease
What chemical processes may be involved in phase 1 of drug metabolism? What is the effect of phase 2 reactions in drug metabolism?
oxidation, reduction, hydrolysis
Describe the action of lipid lowering drugs.
HMG coA reductase inhibitors (simvastatin, atorvastatin)
inhibit cholesterol synthesis in the liver - reduce total cholesterol and LDL cholesterol
side effects: possible myositis with some drug interactions - includes antifungals
Describe the action of anti-arrhythmic drugs.
Beta-adrenergic blockers (B blockers)
-atenolol - selective - B1 only
-propanolol - non-selective - B1 and B2
prevent increase in heart rate - cause postural hypotension, prevent unusual heart rhythms which can lead to heart attacks
reduce heart efficiency -> make heart failure worse
block beta receptors in lungs -> make asthma worse or difficult to treat
Other examples: amiodarone, verapamil
Describe the action of diuretic drugs.
thiazide diuretics (bendroflumethiazide)
loop diuretics (frusemide)
increase salt and water LOSS -> reduce plasma volume, reduce cardiac workload
side effects: can lead to Na/K imbalance if not monitored carefully
Describe the action of nitrate drugs.
short acting - glyceryl trinitrate (GTN)
long acting - isosorbide mononitrate
dilate veins -> reduce preload to the heart
dilate resistance arteries -> reduce cardiac workload (afterload), reduce cardiac oxygen consumption
dilate colateral coronary artery supply -> reduce anginal pain
INACTIVATED BY FIRST PASS METABOLISM ie must administer transdermal, sublingual, intravenous
works in mins as a spray - short acting
works for many hours as a transdermal patch
short shelf life
side effects: headache
Describe the action of calcium channel blocker drugs.
block calcium channels in smooth muscle
-some more active on heart muscle - slow conduction of pacing impulses - verapamil
-some more active on peripheral blood vessels - relaxation and vasodilation - nifedipine, amlodipine
side effects: those acting on peripheral blood vessels cause gingival hyperplasia