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Unasyn Dosage

Generic name: AMPICILLIN SODIUM 100mg in 1mL, SULBACTAM SODIUM 50mg in 1mL
Dosage form: injection, powder, for solution
Drug class: Beta-lactamase inhibitors

Medically reviewed by Last updated on Mar 29, 2023.

The pharmacy bulk package is for preparation of solutions for IV infusion only. UNASYN should be administered by slow intravenous injection over at least 10–15 minutes or can also be delivered in greater dilutions with 50–100 mL of a compatible diluent as an intravenous infusion over 15–30 minutes.

The recommended adult dosage of UNASYN is 1.5 g (1 g ampicillin as the sodium salt plus 0.5 g sulbactam as the sodium salt) to 3 g (2 g ampicillin as the sodium salt plus 1 g sulbactam as the sodium salt) every six hours. This 1.5 to 3 g range represents the total of ampicillin content plus the sulbactam content of UNASYN, and corresponds to a range of 1 g ampicillin/0.5 g sulbactam to 2 g ampicillin/1 g sulbactam. The total dose of sulbactam should not exceed 4 grams per day.

Pediatric Patients 1 Year of Age or Older

The recommended daily dose of UNASYN in pediatric patients is 300 mg per kg of body weight administered via intravenous infusion in equally divided doses every 6 hours. This 300 mg/kg/day dosage represents the total ampicillin content plus the sulbactam content of UNASYN, and corresponds to 200 mg ampicillin/100 mg sulbactam per kg per day. The safety and efficacy of UNASYN administered via intramuscular injection in pediatric patients have not been established. Pediatric patients weighing 40 kg or more should be dosed according to adult recommendations, and the total dose of sulbactam should not exceed 4 grams per day. The course of intravenous therapy should not routinely exceed 14 days. In clinical trials, most children received a course of oral antimicrobials following initial treatment with intravenous UNASYN. (see CLINICAL STUDIES section).

Impaired Renal Function

In patients with impairment of renal function the elimination kinetics of ampicillin and sulbactam are similarly affected, hence the ratio of one to the other will remain constant whatever the renal function. The dose of UNASYN in such patients should be administered less frequently in accordance with the usual practice for ampicillin and according to the following recommendations:

TABLE 3 UNASYN Dosage Guide for Patients with Renal Impairment
Creatinine Clearance
Half-Life (Hours)
Recommended UNASYN Dosage



1.5–3 g q 6h–q 8h



1.5–3 g q 12h



1.5–3 g q 24h

When only serum creatinine is available, the following formula (based on sex, weight, and age of the patient) may be used to convert this value into creatinine clearance. The serum creatinine should represent a steady state of renal function.


weight (kg) × (140 – age)

72 × serum creatinine


0.85 × above value

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.