PENICILLIN-2
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PENICILLIN-2 (PENICILLIN-2).
Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity, and activating autolytic enzymes.
| Metabolism | Primarily eliminated unchanged by renal tubular secretion; minor hepatic metabolism to penicilloic acid. |
| Excretion | Renal: 60-80% unchanged; biliary/fecal: minor (10-20%) |
| Half-life | 30-60 minutes; prolonged in renal impairment (up to 10 hours in anuria) |
| Protein binding | 50-65% bound, primarily to albumin |
| Volume of Distribution | 0.3-0.5 L/kg; low Vd indicates limited tissue penetration |
| Bioavailability | Oral: 60-70% (decreased with food); IM: 70-85% |
| Onset of Action | IV: immediate; IM: 15-30 min; oral: 30-60 min |
| Duration of Action | IV/IM: 4-6 hours; oral: 6-8 hours |
| Molecular Weight | 356.37 |
250 mg orally every 6 hours or 500 mg orally every 8 hours for mild to moderate infections; intravenous dosing: 1-2 million units every 4-6 hours.
| Dosage form | FOR SOLUTION |
| Renal impairment | For CrCl 10-50 mL/min: administer every 8-12 hours; for CrCl <10 mL/min: administer every 12-18 hours; hemodialysis: give after dialysis. |
| Liver impairment | No specific Child-Pugh based dose adjustment; use with caution in severe hepatic impairment. |
| Pediatric use | For children >1 month: 25-50 mg/kg/day orally divided every 6-8 hours; severe infections: 100-250 mg/kg/day IV divided every 4-6 hours; maximum 12 g/day. |
| Geriatric use | No specific dose adjustment except for renal function; monitor renal function and adjust dose accordingly. |
| 1st trimester | Penicillin is generally considered safe during the first trimester; no increased risk of major congenital malformations has been demonstrated in human studies. |
| 2nd trimester | Penicillin is safe in the second trimester; no fetal toxicity reported at standard doses. |
| 3rd trimester | Penicillin is safe in the third trimester; no known adverse effects on the fetus, but caution near delivery due to potential alteration of neonatal gut flora. |
Clinical note
Comprehensive clinical and safety monograph for PENICILLIN-2 (PENICILLIN-2).
| Placental transfer | Penicillin crosses the placenta readily, achieving therapeutic concentrations in fetal tissues and amniotic fluid. |
| Breastfeeding | Penicillin is excreted into breast milk in small amounts; unlikely to cause adverse effects in the nursing infant. May occasionally cause diarrhea or allergic reaction. Use with caution in infants with known hypersensitivity. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Known hypersensitivity to penicillinsHistory of immediate hypersensitivity reaction (e.g., anaphylaxis) to any beta-lactam antibiotic
| Precautions | Hypersensitivity reactions including anaphylaxis, Severe cutaneous adverse reactions (e.g., Stevens-Johnson syndrome), Clostridioides difficile-associated diarrhea, Renal impairment requiring dose adjustment, Neurologic toxicity with high doses (seizures) |
| Food/Dietary | No significant food interactions. Can be taken with or without food. |
| Clinical Pearls |
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| Lactation Rating | L1 - Safe |
| Teratogenic Risk | Penicillin is generally considered low risk; no significant teratogenic effects have been consistently reported in first trimester. Animal studies show no fetal harm. Use is considered safe across all trimesters when indicated. |
| Fetal Monitoring | Monitor maternal renal function and signs of allergic reaction. In prolonged use, monitor for superinfection. Fetal monitoring is not specifically required beyond routine prenatal care. |
| Fertility Effects | No known adverse effects on fertility. Penicillin is not associated with impairment of reproductive function in animal studies or human data. |
| Penicillin-2 (benzathine penicillin G) is indicated for syphilis and group A streptococcal infections. Intramuscular injection only; avoid intravenous administration. Monitor for Jarisch-Herxheimer reaction. Dose adjustment in renal impairment is not typically required due to slow release. |
| Patient Advice | Complete the full course as prescribed, even if symptoms improve. · Report any rash, difficulty breathing, or swelling immediately. · Avoid alcohol during treatment to minimize side effects. · Do not stop or change the dose without consulting your doctor. · Inform all healthcare providers about this therapy. |