Topical medications Flashcards
Considerations for Topical Drug Administration
Age of patient Area of the body Pathologic changes in the skin Hydration of stratum corneum and skin temperature Vascular supply Role of vehicle
vehicles
Powder Paste Shake lotion Ointment Hydrophilic ointment, cream or lotion Water
when to use topicals
If a patient has a skin disorder covering < 30% of body, the topical medication may be considered.
Three main determinants to choose the right vehicle are
Patient’s skin type
Degree of acuity of the disease
Nature of the lesions
how does skin type impact choice of vehicles
About 50% of individuals have oily skin or seborrhea. They do better with creams, lotions, or shake lotions while the ones with dry skin do better with ointments or pastes.
how does degree of acuity impact choice of vehicle
Acute inflammatory processes are best treted with creams or lotions. If the lesions are weeping, shake lotions are fine.
topical corticosteroid classes
Class I (weakest): Hydrocortisone, prednisolone
Class II: Methylprednisolone aceponate, triamcinolone
Class III: Betamethasone 17-valerate
Class IV (strongest): Clobetasol 17-propionate
side effects of topical steroids
Epidermis : Atrophy Hair follicles: Steroid acne Dermis: Atrophy, striae Pigmentation: Hypopigmentation Vessels: Erythema, telangiectases
which bacteria do topical ABX typically target
Most topical antibiotics are directed against Staphylococcus aureus and Streptococcus pyogenes.
The anaerobic Gram-positive bacterial species Propionibacterium acnes has been linked to acne.
classes of topical antibiotics
Cell wall synthesis inhibitors Ribosome function inhibitors Sulfa drugs Burn treatment agents Miscellaneous
Mupirocin (90% Pseudomonic acid A)
Isolated from Pseudomonas fluorescens
Mupirocin works against GRAM POSITIVE BACTERIA ONLY
Can be used to treat MRSA (although resistance is rising)
Ester linkage is rapidly hydrolyzed hepatically, thus precluding utility as an oral or intravenous antibiotic.
Mupirocin inhibits bacterial isoleucyl-tRNA synthetase.
Polymyxin B
Member of the lipopeptide class of antibiotics.
POLYMYXINS: only active against GRAM NEGATIVE BACTERIA (P. aeruginosa, E. coli, K. pneumoniae)
DAPTOMYCIN: treat GRAM POSITIVE BACTERIA
The polymyxins are highly nephrotoxic and are thus only used topically.
Bind the the lipopolysaccharide in the outer membrane, thus destroying OM integrity.
Bind to the cytoplasmic membrane (to the phosphatidylethanolamine) and make the membrane more permeable.
Bacitracin A
Primarily used against gram positivebacteria S. aureus and Streptococci spp.
Most gram negative organisms are resistant.
Bacitracin interferes with bacterial cell wall synthesis.
Acts by blocking a step in the process whereby the key subunits are transferred from the cytoplasm.
Gramicidin
The Gramicidins are small peptides(15 amino acids)
Some, such as gramicidin S, are cyclic
Others, including Gramicidin A, B, C, and D, are linear
Commercial gramicidin is a mixture of compounds.
Gramicidin S is a powerful antibacterial agent, with broad range against a number of Gram positive and Gram negative microorganisms.
Unfortunately, Gramicidin S is hemolytic, and thus is limited to topical use.
Mechanism of action is believed to be at the cytoplasmic membrane.
The gramicidins behave as ionophoric substances.
The gramicidins self associate, thus forming small PORES that cause leakage of essential cations from the cytoplasm.
Neomycin
Neomycin is extremely nephrotoxic, thus limiting its use to a topical antibiotic
Neomycin has excellent activity against GRAM NEGATIVE BACTERIA and partial activity against GRAM POSITIVE strains.
Like other aminoglycosides, neomycin works by binding to the bacterial 30S ribosomal subunit, thus inhibiting protein synthesis.
