Can Penicillin G Be Given Intravenously?
Yes, penicillin G (benzylpenicillin) is routinely administered intravenously and is the preferred route for serious infections requiring high-dose therapy. 1
FDA-Approved Intravenous Administration Routes
The FDA label explicitly approves multiple IV administration methods for penicillin G 1:
- Continuous intravenous drip for high-dose requirements (add daily dosage to 24-hour fluid requirement and adjust infusion rate accordingly)
- Intermittent IV bolus in divided doses (every 4-6 hours depending on indication)
- IV infusion only for the 20 million unit dosage (this high dose must not be given by other routes)
Clinical Applications Requiring IV Penicillin G
Bacterial meningitis is treated with IV penicillin G 15-20 million units/day, demonstrating that intravenous administration has been standard practice for decades in serious CNS infections. 2
Infective endocarditis guidelines from the American Heart Association recommend aqueous crystalline penicillin G 12-18 million units/24 hours IV either continuously or in 4-6 equally divided doses for highly penicillin-susceptible viridans group streptococci. 2
Congenital syphilis in neonates requires aqueous crystalline penicillin G 100,000-150,000 units/kg/day IV, administered as 50,000 units/kg/dose every 12 hours during the first 7 days of life and every 8 hours thereafter for 10 days. 2
Older infants and children with congenital syphilis or neurologic involvement require aqueous crystalline penicillin G 200,000-300,000 units/kg/day IV, administered as 50,000 units/kg every 4-6 hours for 10 days. 2
Pharmacokinetic Advantages of IV Administration
Continuous IV infusion provides more stable plasma concentrations compared to intermittent dosing, which is particularly important for beta-lactam antibiotics where efficacy correlates with time above the minimum inhibitory concentration. 3
Recent pharmacokinetic studies demonstrate that benzylpenicillin exhibits concentration-dependent clearance, with increased clearance at very low concentrations—making sustained IV administration advantageous for maintaining therapeutic levels. 4
Practical Preparation Guidelines
Reconstitution concentrations can range from 50,000 to 1,000 units/mL depending on clinical need, with higher concentrations (up to 100,000 units/mL) suitable for intramuscular use to minimize injection volume, while lower concentrations are used for IV infusion. 1
Stability considerations: All penicillin solutions should be stored refrigerated and may be kept for seven days without significant potency loss. Penicillins are rapidly inactivated in carbohydrate solutions at alkaline pH, so avoid mixing with dextrose-containing solutions. 1
Routes to Avoid for High-Dose Therapy
The 20 million unit dosage must only be administered by IV infusion—never intramuscularly, as this would require excessive injection volumes and cause severe tissue damage. 1
Intrathecal use is mentioned in the FDA label but requires highly individualized consideration due to possible irritating effects, with IV supplemented by IM being the preferred route for bacterial meningitis rather than direct intrathecal administration. 1