Intravenous Ampicillin Dosing Guidelines
The recommended intravenous dose of ampicillin for adults is 2 grams every 4-6 hours, with adjustments based on infection severity, patient characteristics, and renal function. 1
Adult Dosing
- Standard adult dosing: 100-200 mg/kg/day divided every 6 hours (typically 1-2 grams every 6 hours) 2, 1
- Severe infections: Up to 12 grams daily in divided doses every 4-6 hours 3, 1
- Bacterial meningitis: 150-200 mg/kg/day in equally divided doses every 3-4 hours 1
- Septicemia: 150-200 mg/kg/day in divided doses every 3-4 hours 1
- Enterococcal infections: 12 grams IV daily continuously or in 6 divided doses 3
Pediatric Dosing
Neonatal Dosing (≤28 days):
Based on gestational age and postnatal age 2, 3, 1:
| Postnatal Age | Weight | Recommended Dose |
|---|---|---|
| ≤7 days | ≤2000 g | 50 mg/kg/day divided every 12 hours |
| ≤7 days | >2000 g | 75 mg/kg/day divided every 8 hours |
| >7 days | <1200 g | 50 mg/kg/day divided every 12 hours |
| >7 days | 1200-2000 g | 75 mg/kg/day divided every 8 hours |
| >7 days | >2000 g | 100 mg/kg/day divided every 6 hours |
Infants and Children:
- Standard dosing: 100-200 mg/kg/day divided every 6 hours 2, 3, 1
- Bacterial meningitis: 150-200 mg/kg/day in equally divided doses every 3-4 hours 1
Administration Guidelines
- Direct IV administration: Reconstitute with appropriate diluent and administer slowly:
- 250-500 mg vials: Administer over 3-5 minutes
- 1-2 gram vials: Administer over 10-15 minutes 1
- IV infusion: Dilute in compatible IV solutions (0.9% sodium chloride, 5% dextrose) 1
- Stability: Solutions maintain potency for up to 8 hours at room temperature or 24-48 hours when refrigerated 1
Special Considerations
Renal Impairment
- Ampicillin half-life increases significantly with declining renal function 4
- For severe renal impairment (CrCl 7-30 ml/min): Consider reducing frequency to twice daily 4
- For hemodialysis patients: Administer every 24 hours, with doses given after hemodialysis on dialysis days 4
Duration of Therapy
- Minimum of 48-72 hours beyond clinical improvement 1
- For Group A beta-hemolytic streptococcal infections: Minimum 10-day treatment course 1
- For endocarditis: 4-6 weeks of therapy 2
Important Precautions
- More rapid IV administration than recommended may result in seizures 1
- Use freshly prepared solutions within one hour of preparation for optimal potency 1
- For neonates, avoid using bacteriostatic water for injection as a diluent 1
- Monitor for hypersensitivity reactions, particularly in patients with penicillin allergy
Following these guidelines will help ensure optimal therapeutic outcomes while minimizing adverse effects when administering intravenous ampicillin.