Penamecillin, an acetoxymethyl ester of benzylpenicillin, is a

prodrug A prodrug is a pharmacologically inactive medication or compound that, after intake, is metabolized (i.e., converted within the body) into a pharmacologically active drug. Instead of administering a drug directly, a corresponding prodrug can be ...

processed to

benzylpenicillin Benzylpenicillin, also known as penicillin G (PenG) or BENPEN, is an antibiotic used to treat a number of bacterial infections. This includes pneumonia, strep throat, syphilis, necrotizing enterocolitis, diphtheria, gas gangrene, leptospiro ...

by esterases. It has no detectable teratogenic risk to the fetus.

References

Penicillins {{antibiotic-stub