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MP321 > formulations of anti-microbials > Flashcards

formulations of anti-microbials Flashcards

1
Q

characteristics of a topical drug

A
  • low MW (less than 500)
  • moderately lipophilic (logP 1-4)
  • effective at low dose (daily dose of less than 10mg)
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2
Q

liquid formulations

A
  • single-phase solutions/lotions
  • rapid short term input of permeant into skin
  • poor residence time on the skin
  • evaporation of solvent (alcoholic vehicle)
    EXAMPLES: erythromycin solution, clindamycin lotion
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3
Q

semi-solid formulations

A
  • ointments, gels, creams
  • good residence time on the skin
  • good acceptance from patients
    semi-solid base:
  • hydrophobic (liquid paraffin, glycerides, waxes)
  • hydrophilic (polyethylene glycol PEG)
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4
Q

ointments

A
  • hydrophobic, fatty preparations
  • highly occlusive (non-permeable)
  • used on dry lesions
  • prolonged drug delivery
  • messy to use
    EXAMPLES: mupirocin, fusidic acid (staphylococcus infection: impetigo)
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5
Q

gels

A
  • formed from a liquid phase that is thickened with other components (i.e. PEG, polymers: carbomer)
  • liquid phase maybe alcoholic, solvent may evaporate
    EXAMPLE: metronidazole gel (rosacea)
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6
Q

creams

A
  • made of 2 phased emulsion: water-in-oil or oil-in-water
  • water-in-oil emulsions less greasy than ointments
  • easier to apply
  • can be washed off
  • less occlusive than ointments
  • less beneficial in dry skin conditions
    EXAMPLES: mupirocin, neomycin, fusidic acid
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7
Q

solid formulations

A
  • spray powders
  • incorporate a volatile solvent (ethanol) that dissolves some drug prior to evaporation
    EXAMPLE: miconazole nitrate (fungal skin infection: athletes foot)
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8
Q

nail solid formulations

A
  • nail lacquer
  • keratolytic components (urea) to increase diffusion of the drug through the nail plate
    EXAMPLE: amorolfine
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9
Q

eye solutions

A
  • easy to administer
  • homogeneous (better dose uniformity)
  • rapidly drained out of eye
  • lack of efficacy
    EXAMPLES: chloramphenicol, ciprofloxacin (corneal ulcers)
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10
Q

eye ointments

A
  • mainly used of lipophilic excipients (petrolatum, lanolin)
  • reduce drug drainage caused by tear flow
  • increase of corneal residence time
  • sustained drug release (2-4 hrs)
  • more difficult to administer than solutions
  • blurring of vision
    EXAMPLES: chloramphenicol, ciprofloxacin
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11
Q

ear solutions

A
  • viscous formulations
  • increase residence time of the formulation
  • prolonged contact with the area of infection
    EXAMPLES: chloramphenicol, clotrimazole (otitis)
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12
Q

nose formulations

A
  • creams, ointments
  • mucocilliary clearance (removal of the drug from the nasal cavity)
  • bioadhesion needed for increased nasal residence time
    EXAMPLES: mupirocin, chlorhexidine + neomycin (staphylococci)
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13
Q

oropharyngeal formulations

A
  • solutions, gels, suspensions, mucoadhesive buccal tablets
  • suspensions deposit antimicrobial drug on mucosa surface
  • improvement of residence time of drug but dissolution needed prior permeation
    EXAMPLES:
  • miconazole gel and mucoadhesive tablets (fungal infections: thrush, candidiasis)
  • Nystatin suspension (fungal)
  • chlorhexidine mouth wash
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14
Q

vagina formulations

A
  • gels, creams, pessaries, ovules
  • pessary: solid, single-dose formulation of ovoid shape
  • ovules (vaginal capsules): solid single-dose formulations
  • treatment of local infections with low dose than with oral administration
  • no need of absorption of drugs for local action
  • release of the drugs influenced by varying volumes of vaginal fluid
    EXAMPLES:
  • clotrimazole (cream/pessary)
  • antifungal miconazole (ovule)
  • metronidazole (gel)
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15
Q

oral administration

A
  • drug absorption through epithelia and mucosa of GI tract
  • most convenient and safest form
  • possibility of irregular absorption of certain drugs
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16
Q

tablets

A
  • accurate dosing of the drug
  • convenient to handle
  • easy to take
  • controlled release of the drug
  • poor bioavailability of some drugs
  • local irritants effects the GI tract
17
Q

capsules

A
  • accurate dosing of drug
  • drug released faster than tablets
  • use of colour for identification
  • easy to swallow
  • shell masks taste
  • good patient compliance
  • bulky material can result in large capsule size
  • susceptible yo moisture
18
Q

powders

A
  • reconstituted just before use to avoid chemical degradation
  • faster dissolution rate than tablets/capsules
  • less convenient to carry and administer
19
Q

suspensions

A
  • drug absorption faster than tablets/capsules
  • insoluble solids act as reservoir
  • slow/prolonged release of drug
  • risk of sedimentation
20
Q

syrup

A
  • drug already dissolved
  • absorption faster than solid dosage forms
  • masks unpleasant taste
  • easy to adjust dose for child’s weight
  • risk of deterioration
  • inaccuracy in doses as patient is measuring with spoon
21
Q

rectal administration

A
  • suppositories
  • for drugs that are inactivated by GI fluids/liver when given orally
  • good route to administer when vomiting
  • faster systemic response
  • patient unacceptability
  • drug absorption: irregular/difficult to predict
22
Q

parenteral administration

A
  • intramuscular and intravenous administrations
  • must be sterile
  • preferred route when rapid absorption is essential
  • sterile solutions/suspensions of drugs in water
23
Q

injections

A
  • sterile solutions, emulsions, suspensions in water, non-aqueous liquids
  • injected in less than 15 mins
24
Q

infusions

A
  • aqueous solutions
  • large volumes: 100-1000 ml
  • injected in more than 15 mins
25
Q

depot preparation

A
  • dispersion of drug in oily vehicle
  • intramuscular injection deep into skeletal muscle
  • viscous formulation
  • large volume
  • slow release of antibiotic for weeks
26
Q

benzathine penicillin G

A
  • patients who have had acute rheumatic fever and need prophylaxis against further streptococcal infections
27
Q

liposomes

A
  • spherical vesicles which a lipid bilayer membrane delimitates a central aqueous compartment
  • carry hydrophobic and lipophilic drugs
  • they form when phospholipids are exposed to an aqueous environment
28
Q

fungizone [amphotericin]

A
  • antifungal agent used to treat invasive fungal infections (candidiasis)
  • sterile lyophilised powder
  • micellar dispersion of amphotericin and sodium deoxycholate
  • administered as an IV infusion over 20-30 mins
29
Q

micelle

A

assembly of surfactant molecules in water with hydrophilic head regions in contact with surrounding solvent sequestering the hydrophobic tail regions in micelle centre

30
Q

adverse effects of amphotericin

A
  • renal toxicity: >80% of patients
  • haematological toxicity: severe thrombocytopenia, leukopenia, haemoglobin reduction)
  • cardiovascular toxicity (cardiac arrest)
31
Q

amphotericin mode of action

A
  • binds to ergosterol present in fungal cell membranes giving a therapeutic effect
  • also binds to cholesterol present in mammalian healthy cells membranes making it toxic
32
Q

AmBisome

A
  • small unilamellar vesicle
  • single bilayer, less than 100nm
  • drug intercalated within the liposome membrane
  • 80% less toxic than fungizone
  • prolonged circulation in vivo
  • direct interaction with fungal cells
  • minimal interaction with mammalian cells
  • minimal exposure of non-target tissues
    disadvantages:
  • interaction with blood opsonin
  • liposomes end up in the tissue of mononuclear phagocytosis system (MPS) mostly fixed to macrophages in the liver + spleen

MP321 (11 decks)

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