Phenobarbital Ampule Content
A standard 1-mL ampule of phenobarbital sodium contains 130 mg 1.
Available Formulations
Phenobarbital sodium injection is commercially available in two concentrations 1:
- 130 mg/mL (standard concentration)
- 65 mg/mL (alternative concentration)
The 130 mg/mL formulation is the most commonly used preparation for both intramuscular and slow intravenous administration.
Formulation Details
Each mL of the 130 mg/mL solution contains 1:
- Phenobarbital sodium: 130 mg
- Alcohol: 0.1 mL
- Propylene glycol: 0.678 mL
- Benzyl alcohol: 0.015 mL
- Water for Injection (with hydrochloric acid for pH adjustment)
- pH range: 9.2-10.2
Clinical Context
This concentration allows for precise dosing in various clinical scenarios:
- Loading doses for seizures typically require 15-20 mg/kg 1, 2, which would necessitate multiple ampules for most adults
- Maintenance dosing for anticonvulsant therapy targets serum levels of 10-25 µg/mL 3, 1
- The 130 mg/mL concentration facilitates administration of therapeutic doses while minimizing injection volume, which is particularly important since no more than 5 mL should be injected at any single intramuscular site 1
Critical safety note: The solution should not be used if discolored or precipitated 1, and intravenous administration must not exceed 60 mg/min in adults to avoid cardiovascular and respiratory complications 1.