Considerations for selecting an antibiotic include

Efficacy/ spectrum; incidence of resistance (ie. penicillinase inhibition); administration: route, schedule, etc (OS will sometimes inject ABs into the buttocks); Penetration at injection site (a walled abscess is not penetrable to Abs, the site must be accessed by non AB means); Adverse Drug Reactions (ADR) profile/cross-reactivity (allergy); drug interaction profile (esp. with “old” drugs like erythromycin; cost (generic vs. brand name).

*Both incidence of resistance and the penetration at the injection site are important as to why an AB may not work..


Cost Comparison, Macrolide Abs:

Azithromycin (Zithromax) costs $49 (5 days)

Clarithromycin (Biaxin) costs $35 (7 days)

Erythromycin (Generic) costs $7 (7 days)

(pseudomembranous colitis… priceless!)

Category: Pharmacology Notes