PENICILLIN-VK
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PENICILLIN-VK (PENICILLIN-VK).
Penicillin VK inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity, and activating autolytic enzymes.
| Metabolism | Hepatic metabolism to inactive metabolites (minor pathway); primarily excreted unchanged in urine via renal tubular secretion. |
| Excretion | Renal: 20-40% unchanged via tubular secretion; hepatic metabolism to penicilloic acid; biliary/fecal: minimal (<5%). |
| Half-life | 0.5 hours (normal renal function); prolonged to 3-10 hours in severe renal impairment (CrCl <10 mL/min). |
| Protein binding | 60-80% bound to serum albumin. |
| Volume of Distribution | 0.3-0.4 L/kg; reflects distribution into extracellular fluid and limited tissue penetration except in inflamed meninges. |
| Bioavailability | Oral: 60-75% (varies with food intake; reduced by presence of food). |
| Onset of Action | Oral: 30-60 minutes; IM: 15-30 minutes; rapid bactericidal effect. |
| Duration of Action | 4-6 hours (oral); 6-8 hours (IM); clinical effect may persist up to 12 hours in renal impairment. |
| Molecular Weight | 350.45 |
250-500 mg orally every 6-8 hours for mild to moderate infections; 500 mg orally every 6 hours for severe infections (e.g., streptococcal pharyngitis, skin infections).
| Dosage form | TABLET |
| Renal impairment | No adjustment needed for GFR >50 mL/min. For GFR 10-50 mL/min: administer every 8-12 hours. For GFR <10 mL/min: administer every 12-16 hours. Hemodialysis: 500 mg after dialysis. |
| Liver impairment | No dose adjustment required for Child-Pugh Class A or B. For Child-Pugh Class C: use with caution; consider dose reduction based on clinical response (limited data). |
| Pediatric use | For children weighing <40 kg: 25-50 mg/kg/day orally divided every 6-8 hours; maximum 3 g/day. For children weighing ≥40 kg: adult dosing applies. |
| Geriatric use | No specific dose adjustment recommended; use lowest effective dose due to age-related renal function decline. Monitor renal function and adjust per renal adjustment guidelines. |
| 1st trimester | Generally considered safe; no increased risk of major congenital malformations reported. |
| 2nd trimester | Safe; used for infections without known fetal harm. |
| 3rd trimester | Safe; avoid exposure near delivery due to risk of neonatal sensitization or diarrhea. |
Clinical note
Comprehensive clinical and safety monograph for PENICILLIN-VK (PENICILLIN-VK).
| Placental transfer | Penicillin V crosses the placenta readily; achieves fetal serum concentrations approximately 30-50% of maternal serum levels. |
| Breastfeeding | Penicillin V is excreted into breast milk in low concentrations (less than 1% of the maternal dose). Generally considered compatible with breastfeeding; may alter infant gut flora or cause diarrhea. Monitor infant for rash, diarrhea, or candidiasis. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
History of immediate-type hypersensitivity reaction (e.g., anaphylaxis, urticaria) to any penicillinKnown hypersensitivity to cephalosporins due to possible cross-reactivity
| Precautions | Serious hypersensitivity reactions (anaphylaxis) can occur; contraindicated in patients with prior penicillin allergy., Superinfection with resistant organisms may develop with prolonged use., Use with caution in patients with renal impairment (dose adjustment may be needed)., Assess renal, hepatic, and hematologic function periodically during prolonged therapy., May interfere with oral contraceptives; alternative contraception recommended. |
| Food/Dietary | Absorption is decreased by food; take on an empty stomach. Avoid acidic beverages (fruit juices, soda) as they may degrade the drug. No other significant food interactions. |
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| Lactation Rating |
| L1 |
| Teratogenic Risk | Penicillin VK (phenoxymethylpenicillin) is classified as FDA Pregnancy Category B. Animal reproduction studies have not demonstrated a risk to the fetus, and there are no adequate and well-controlled studies in pregnant women. However, penicillin antibiotics are generally considered safe during pregnancy. No known teratogenic effects have been associated with penicillin VK in any trimester. Use during pregnancy should be reserved for clear indications. |
| Fetal Monitoring | No specific maternal-fetal monitoring is required beyond standard clinical assessment. Monitor for allergic reactions, including rash and anaphylaxis. In long-term therapy, assess renal function and complete blood count periodically. For fetal monitoring, no special surveillance is indicated. |
| Fertility Effects | Penicillin VK has no known adverse effects on fertility in animal studies or human data. No impact on spermatogenesis or oogenesis has been reported. |
| Clinical Pearls | Penicillin VK is acid-stable and best absorbed on an empty stomach; administer 1 hour before or 2 hours after meals. Dose adjustment needed in severe renal impairment (CrCl <10 mL/min). Not effective against beta-lactamase-producing organisms. Use with caution in patients with history of cephalosporin allergy (cross-reactivity ~1-10%). For streptococcal pharyngitis, treat for 10 days. Take full 10-day course even if symptoms resolve. |
| Patient Advice | Take this medication on an empty stomach, at least 1 hour before or 2 hours after a meal. · Complete the entire prescribed course, even if you feel better, to prevent resistance. · Shake the oral suspension well before each dose. · Report any rash, itching, or diarrhea immediately. · Avoid alcohol while taking this medication. · Store at room temperature away from moisture and heat. |