Important Facts about Natural Penicillins
- Natural penicillins have a very short half-life and must be dosed frequently or given by continuous infusion. Long-acting depot formulations (procaine, benzathine) are available. It is important to know the differences among these formulations, because the doses vary considerably. It is even more important not to give procaine or benzathine products intravenously, as this can be fatal.
- Penicillin V is the oral form of penicillin G. Other drugs have supplanted it in most, but not all, uses.
- Penicillin G remains the drug of choice for syphilis.
- Due to resistance, penicillin is a poor empiric choice for most infections. Not all medical textbooks have been updated to reflect the changes in penicillin use that have resulted from widespread resistance.
What They're Good For
Syphilis, particularly neurosyphilis. During penicillin shortages, hospitals often reserve its use for this indication. Penicillin is also used in susceptible streptococcal infections such as pharyngitis or endocarditis.
Don't Forget!
Other, more conveniently dosed narrow spectrum beta-lactams are available for bugs treatable with penicillin.