Pharmacodynamic properties
Its mode of action is by prevention of cell wall synthesis during bacterial cell growth and is primarily bactericidal. The in-vitro spectrum of activity is mainly within the gram-positive class of bacteria eg Staphylococcus spp, Streptococcus spp, Clostridium spp, Bacillus spp etc.
Pharmacokinetic properties
Penethamate hydriodide is a prodrug which releases benzylpenicillin quantitatively at hydrolysis. The pKa-value of penethamate hydriodide is 8.4. This means that in aqueous solution at physiological pH of 7.2, 8.2% of the drug will be present as the uncharged molecule while 91.8% will be present as the ion. In aqueous solution penethamate is hydrolysed to form benzylpenicillin and diethylaminoethanol. After intramuscular injection the prodrug itself as well as the released alcohol, diethylaminoethanol has not shown any unexpected pharmacological effects.