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Permapen (Penicillin G Benzathine) - Description and Clinical Pharmacology

 
 



PERMAPEN® ISOJECT®
(Penicillin G Benzathine)
Injectable Suspension
1,200,000 units
For lntramuscular Use Only

STORE BETWEEN 2°–8°C (36°–46°F)

SHAKE WELL BEFORE USING

DESCRIPTION

Permapen® (Penicillin G Benzathine) Injectable Suspension, a sterile antibacterial agent, is a repository penicillin compound which provides blood levels for long periods following its intramuscular injection. This property is the result of its extremely low solubility in water. Each milliliter contains 600,000 units of penicillin G benzathine; 0.006 grams sodium citrate; 0.003 grams polyvinylpyrrolidone; 0.010 grams lecithin, and 0.003 grams sodium carboxymethylcellulose in an aqueous suspension. Permapen also contains methylparaben 0.09% and propylparaben 0.01% as preservatives.

Chemically, Permapen is 3,3-dimethyl-7-oxo-6-(2-phenylacetamido)-4 thia-l azabicyclo [3.2.0] heptane-2-carboxylic acid compound with N,N'-dibenzylethylenediamine (2:1) tetrahydrate. It is prepared by the reaction of dibenzyl-tetrahydrate-ethylenediamine with 2 molecules of penicillin G.

It has a molecular weight of 981.19 and the following chemical structure:

Formula

C16H20N2•2C16Hl8N2O4S•4H2O

Penicillin G benzathine occurs as a white crystalline powder and is very slightly soluble in water.

The pH of the injectable suspension is between 5.0–7.5.

CLINICAL PHARMACOLOGY

Intramuscular penicillin G benzathine is absorbed very slowly into the blood stream from the intramuscular site and converted by hydrolysis to penicillin G. This combination of hydrolysis and slow absorption results in blood serum levels much lower than those of other parenteral penicillins.

Approximately 60% of penicillin G is bound to serum protein. The drug is distributed throughout the body tissues in widely varying amounts. Highest levels are found in the kidneys with lesser amounts in the liver, skin, and intestines. Penicillin G penetrates into all other tissues and the spinal fluid to a lesser degree. With normal kidney function the drug is excreted rapidly by tubular excretion. A small amount is secreted into the bile. In neonates and young infants, and in individuals with impaired kidney function, excretion is considerably delayed.

Microbiology

Penicillin G exerts a bactericidal action against penicillin-susceptible microorganisms during the stage of active multiplication. It acts through the inhibition of biosynthesis of cell wall mucopeptide. It is not active against the penicillinase-producing bacteria, which includes many strains of staphylococci.

While in vitro studies have demonstrated the susceptibility of most strains of the following organisms, clinical efficacy for infections other than those included in the INDICATIONS AND USAGE section has not been documented. Penicillin G exerts high in vitro activity against staphylococci (except penicillinase-producing strains), streptococci (groups A, C, G, H, L, and M), and pneumococci. Other organisms sensitive to penicillin G are: Corynebacterium diphtheriae, Bacillus anthracis, Clostridia, Actinomyces bovis, Streptobacillus moniliformis, Listeria monocytogenes, and Leptospira. Treponema pallidum is extremely sensitive to the bactericidal action of penicillin G.

Penicillin acts synergistically with gentamicin or tobramycin against many strains of enterococci.

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