Clinical beta
FMBM is currently in clinical beta. Content is for professional review/testing and must not replace local protocols, senior clinical judgment, or official prescribing references.
Drug Monograph
Penicillin V
Natural penicillin (oral β-lactam)
Indication
GAS pharyngitis/tonsillitis • Mild streptococcal skin infection • Mild dental/oropharyngeal infection • Rheumatic fever prophylaxis
INDICATIONS (CORE USE)
GAS pharyngitis/tonsillitis • Mild streptococcal skin infection • Mild dental/oropharyngeal infection • Rheumatic fever prophylaxis
ADULT DOSE (STANDARD)
250–500 mg PO q6–8h Pharyngitis: 250 mg PO BID–TID × 10 days (GAS)
MAX DOSE
Usual: 2 g/day — adult: up to 4 g/day in selected cases (per guideline)
Route
PO only
PEDIATRIC DOSE
Pharyngitis: 250 mg BID–TID × 10 days — Mild infections: 15–30 mg/kg/day divided (per pediatric reference)
Must-not-miss safety points
Major warning
- Hypersensitivity (anaphylaxis risk) - Not for severe/systemic infection (e.g., sepsis, meningitis, endocarditis) - Reduced absorption with food → take on empty stomach - Narrow spectrum → ineffective against resistant organisms - Adherence critical → rheumatic fever risk (GAS)
USE IF: Group A streptococcal (GAS) pharyngitis/tonsillitis; mild streptococcal skin infection; mild dental/oropharyngeal infection; rheumatic fever prophylaxis when oral therapy is appropriate. AVOID IF: Severe or systemic infection requiring IV therapy; vomiting or malabsorption that prevents reliable oral absorption; penicillin anaphylaxis. Acid-stable oral natural penicillin—stewardship-friendly when spectrum and severity match.
ADULT DOSE
Standard: 250–500 mg PO q6–8h GAS pharyngitis: 250 mg PO BID–TID × 10 days Rheumatic prophylaxis: 125–250 mg BID Skin/dental: 250–500 mg PO q6–8h IV formulation not available.
PEDIATRIC DOSE
Pharyngitis: 250 mg BID–TID × 10 days. Weight-based mild infections: 15–30 mg/kg/day in divided doses (per pediatric reference).
MAX DOSE
Usual: 2 g/day Adult: up to 4 g/day in selected cases (per guideline)
Practical Note
- Renal: usually no adjustment; severe impairment — consider q8–12h or lower total daily dose - Hepatic: no routine adjustment - Best on empty stomach: 1 h before or 2 h after food - Space doses evenly; use accurate measuring device for suspension - Absorption plateaus above ~500 mg per dose
Clinical warnings
Adverse effects
Pediatrics
Pharyngitis: 250 mg BID–TID × 10 days — Mild infections: 15–30 mg/kg/day divided (per pediatric reference)
Pregnancy
Safe when clinically indicated; first-line oral option for streptococcal pharyngitis in pregnancy when appropriate. Breastfeeding generally compatible — monitor infant for diarrhea, rash, or thrush. Pregnancy: Safe; first-line for streptococcal pharyngitis in pregnancy when oral therapy appropriate.
Lactation
Compatible — monitor infant for diarrhea, rash, or thrush.
Renal impairment
Usually no dose change; severe impairment may need interval extension or lower total daily dose with prolonged/high-dose therapy.
Hepatic impairment
No routine dose adjustment.
Elderly
Usually safe; monitor renal function and drug interactions (e.g., warfarin, methotrexate).
Give on empty stomach for optimal absorption (1 h before or 2 h after meals). PO tablets/suspension only — no IV formulation. Space doses evenly. Shake suspension well; measure with an accurate device. Not applicable for infusion.
Clinical Picture
No well-defined toxic threshold; wide therapeutic margin. Features: GI upset ± neurotoxicity in severe renal failure; allergic reactions may occur.
Immediate Actions
- Stop drug - Supportive care
Antidote
No specific antidote — supportive care
Decontamination
Acute massive ingestion — contact poison center; charcoal rarely indicated.
Escalation
Fluids and supportive care; benzodiazepines if seizures; anaphylaxis protocol if needed; dialysis only in extreme overdose with renal failure per nephrology/toxicology.
Common mistakes, resistance logic, and bedside traps
FIRST LINE: Oral narrow-spectrum penicillin for mild streptococcal infections and prophylaxis. DOSE — Adult: 250–500 mg PO q6–8h; pharyngitis: 250 mg PO BID–TID × 10 days (GAS). MAX — Usual 2 g/day; adult: up to 4 g/day in selected cases (per guideline). AVOID — Sepsis, meningitis, endocarditis, deep infection; food near dosing. ANTIDOTE — None.
- Oral-only agent — do not substitute for IV penicillin in severe infection - Do NOT use for deep or invasive infections — switch to IV penicillin - Must complete 10 days for GAS pharyngitis - Best taken on empty stomach - Absorption plateaus above 500 mg per dose - Methotrexate toxicity interaction
Stewardship-friendly choice — first-line for confirmed GAS pharyngitis (prevents rheumatic fever). Do not use for systemic toxicity or deep infection. Full 10-day course is critical for rheumatic fever prevention. Oral route only — switch to penicillin G if IV needed. Always ask/document penicillin allergy before prescribing. Poor adherence → consider benzathine penicillin G IM (single-dose alternative).
- Acid-stable oral penicillin - Best absorbed on empty stomach - Doses above ~500 mg have less proportional absorption (plateau) - Minimal metabolism - Primarily renal elimination - Short half-life → requires q6–8h dosing
Binds penicillin-binding proteins (PBPs), inhibiting peptidoglycan cross-linking and bacterial cell wall synthesis — bactericidal in susceptible organisms.
Saudi Arabia
Phenoxymethylpenicillin (generic), Penicillin V (Pen VK)
Global
Penicillin VK, APO-PEN-VK, Penicillin V (generic)
Common trade names are curated examples only — formulations and availability vary. Verify the exact product name with your local pharmacy and national regulator before prescribing or dispensing.
Saudi Arabia
International