Oxacillin, cloxacillin, dicloxacillin and floxacillin are isoxazolyl penicillins that are very similar pharmacologically and offer the advantage of being much more resistant to breakdown in acid and therefore more useful for oral administration. They are all highly resistant to cleavage by β-lactamase.
They vary somewhat in potency and therefore dosage is adjusted accordingly. Absorption from the gastrointestinal tract is about 50-90% on an empty stomach, depending on the drug. This yields peak plasma levels in one hour (T1/2 = 30-60 min). 95% of the circulating drug is bound to plasma.