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Permapen Isoject Dosage

Generic name: penicillin G benzathine
Dosage form: Injectable Suspension 1,200,000 units
Drug class: Natural penicillins

Medically reviewed by Last updated on Apr 4, 2022.

Administer by deep IM injection in the upper outer quadrant of the buttock. In infants and small children, the mid-lateral aspect of the thigh may be preferable. When doses are repeated, vary the injection site (see PRECAUTIONS).

Pediatric Dosage Schedule

In children under 12 years of age, dosage should be adjusted in accordance with the age and weight of the child and the severity of the infection. Under 2 years of age, the dose may be divided between the two buttocks if necessary.

Streptococcal Infections (group A) pharyngitis

A single injection of 900,000 units for older children; l,200,000 units for adults.

Venereal Infections


Primary, secondary, and latent: 2.4 million units (1 dose).

Late Syphilis (tertiary and neurosyphilis)

3 million units at 7 day intervals for a total of 6–9 million units.

Congenital Syphilis (asymptomatic with normal cerebrospinal fluid)

Under 2 years of age–50,000 units/kg body weight in a single dose; ages 2–12 years–adjust dosage based on adult dosage schedule.

Yaws, Bejel, and Pinta

1.2 million units (1 injection).


For rheumatic fever and glomerulonephritis.

Following an acute attack, penicillin G benzathine (parenteral) may be given in doses of 1,200,000 units once a month or 600,000 units every 2 weeks.

Parenteral drug products should be visually inspected for particulate matter and discoloration prior to administration, whenever solution and container permit.

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