Ampicillin administration route

Case A. When a prodrug is pharmacologically inactive and is subject to an important presystemic transformation to the active moiety, it is correct to administer the active moiety by the intravenous route as the reference pharmaceutical form, as long as its behavior (CL,Vd) is identical for both modes of administration. The ratio of dose-normalized AUCs after oral and intravenous administration is the absolute bioavailability of the active moiety. This is, for example, the procedure that was used with ampicillin and its prodrugs ba-campicillin and pivampicillin (107). 

The pharmacology of penicillins differs markedly from compound to compound but has been well reviewed (57). The majority of derivatives, including penicillin G and the antipseudomonal penicillins, are unstable in gastric acid and are not available orally. The isoxazolyl penicillins are relatively acid stable but not consistently well absorbed by the oral route. Nafcillin and oxacillin are poorly absorbed orally cloxacillin, didoxacfllin, and flucloxacillin are more reliable. Penicillin V, ampicillin, and particularly amoxicillin are relatively well absorbed orally. Esters of ampicillin such as bacampicillin, pivampicillin, and talampicillin improve the level of oral absorption of ampicillin to that achieved by amoxicillin. Absorption can be diminished by food after oral administration, however, and peak blood levels, usually achieved after 1 to 2 h, are somewhat delayed after ingestion of food. 

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