AMPICILLIN SODIUM
Clinical safety rating: safe
Probenecid decreases renal tubular secretion of ampicillin Allopurinol may increase the incidence of skin rashes Serious and occasionally fatal hypersensitivity reactions have been reported.
Ampicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death.
| Metabolism | Ampicillin is primarily excreted unchanged in urine (renal elimination); minimal hepatic metabolism. |
| Excretion | Approximately 90% renal excretion via tubular secretion and glomerular filtration; small biliary excretion (<10%); fecal elimination negligible. |
| Half-life | Terminal elimination half-life ~1 hour in healthy adults; prolonged to 2–5 hours in renal impairment (CrCl <10 mL/min) and up to 7–20 hours in anuria; neonatal half-life 2–4 hours. |
| Protein binding | Approximately 20% bound to serum proteins, primarily albumin. |
| Volume of Distribution | 0.3 L/kg, reflecting distribution primarily into extracellular fluid; increased in neonates and inflammation (e.g., meningitis). |
| Bioavailability | Oral: 40–60% (decreased by food); IM: near 100% compared to IV. |
| Onset of Action | IV: immediate; IM: 15–30 minutes; oral: 1–2 hours. |
| Duration of Action | Approximately 4–6 hours; prolonged in renal impairment; dependent on dose and renal function. |
1-2 g IV/IM every 4-6 hours for serious infections; maximum 12 g/day.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 30-50 mL/min: 1-2 g every 6-8 hours; CrCl 15-29 mL/min: 1-2 g every 8-12 hours; CrCl <15 mL/min: 1-2 g every 12-24 hours. |
| Liver impairment | No dose adjustment required for hepatic impairment. |
| Pediatric use | Neonates <7 days: 50 mg/kg/dose IV/IM every 12 hours; 7-28 days: 50 mg/kg/dose every 8 hours; Children: 50-100 mg/kg/day IV/IM divided every 6 hours. |
| Geriatric use | Start at lower end of dosing range; adjust based on renal function; maximum 12 g/day. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Probenecid decreases renal tubular secretion of ampicillin Allopurinol may increase the incidence of skin rashes Serious and occasionally fatal hypersensitivity reactions have been reported.
| FDA category | Human |
| Breastfeeding | Ampicillin is excreted into human breast milk in low concentrations (M/P ratio approximately 0.2). Adverse effects in the nursing infant are rare, but may include diarrhea, candidiasis, or allergic sensitization. The benefits of breastfeeding outweigh potential risks; however, monitor infant for gastrointestinal disturbances. |
| Teratogenic Risk |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | Diarrhea |
| Serious Effects |
["Hypersensitivity to ampicillin, penicillins, or any component of the formulation","Infections caused by penicillinase-producing organisms"]
| Precautions | ["Serious hypersensitivity reactions including anaphylaxis","Clostridium difficile-associated diarrhea (CDAD)","Seizures with high doses or renal impairment","Prolonged use may lead to superinfection"] |
| Food/Dietary | Take on an empty stomach (1 hour before or 2 hours after meals) to maximize absorption. Avoid acidic fruit juices (e.g., orange, grapefruit) which may reduce absorption. No specific food restrictions but high-fat meals may delay absorption. |
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| Ampicillin sodium is classified as FDA Pregnancy Category B. Animal reproduction studies have not demonstrated fetal risk, and there are no adequate and well-controlled studies in pregnant women. Use during pregnancy is generally considered safe, but should be reserved for cases where clearly needed. No known teratogenic effects; however, potential for alterations in gut flora exists. |
| Fetal Monitoring | Monitor maternal renal function and signs of hypersensitivity. No specific fetal monitoring required beyond routine prenatal care. If used during labor, observe for neonatal effects (e.g., diarrhea, rash). |
| Fertility Effects | No known adverse effects on fertility. Ampicillin does not appear to impair reproductive function in animal studies. |
| Clinical Pearls | Ampicillin sodium is a beta-lactam antibiotic; always assess for penicillin allergy before administration. Not effective against beta-lactamase-producing organisms; consider combination with sulbactam if resistance suspected. Monitor renal function as dose adjustment needed in renal impairment. IV administration over 30 minutes to reduce phlebitis risk. May cause false-positive urine glucose tests with Clinitest but not with glucose oxidase methods. |
| Patient Advice | Complete the full course even if you feel better. · Report any signs of allergic reaction: rash, itching, swelling, difficulty breathing. · Take with a full glass of water 1 hour before or 2 hours after meals for best absorption. · Do not take with grapefruit juice as it may affect absorption. · Inform your doctor if you have kidney disease or a history of allergies. · May cause diarrhea; contact doctor if severe or bloody diarrhea occurs. · Use effective birth control if applicable; ampicillin may reduce oral contraceptive efficacy. |