DOSES AND DRUG INTERACTIONS OF PENICILLINS

DOSES OF PENICILLINS:

Most commonly used penicillins have the following doses:

* BENZYL PENICILLIN:

By intramuscular or slow intravenous injection or by infusion:

2.4-4.8 g daily in divided doses

* PHENOXYMETHYL PENICILLIN:

By oral route:

500 mg every 6 hours up to 1g every 6 hours in severe infections.

* AMOXICILLIN:

By mouth:

250mg every 8 hours, doubled in severe infections.

* AMPICILLIN:

By mouth:

0.25g-1g every 6 hours, at least 30 minutes before food.

DRUG INTERACTIONS OF PENICILLINS:

* ALLOPURINOL:

Increased risk of rash when amoxicillin and ampicillin are given with allopurinol.

* ANTIBACTERIALS:

Absorption of phenoxy methyl penicillin is reduced by neomycin.

* CYTOTOXICS:

Penicillins reduce excretion of methotrexate (increased risk of toxicity).

* MUSCLE RELAXANTS:

Piperacillin enhances effects of non depolarising muscle relaxants and suxamethonium.

* PROBENECID:

Excretion of penicillins is reduced by probenecid.

* SULFINPYRAZONE:

Excretion of penicillins is reduced by sulfinpyrazone.