Hetacillin is a beta-lactam

Beta-lactam antibiotic

β-Lactam antibiotics are a broad class of antibiotics, consisting of all antibiotic agents that contains a β-lactam nucleus in its molecular structure. This includes penicillin derivatives , cephalosporins , monobactams, and carbapenems...

. Hetacillin is a prodrug

Prodrug

A prodrug is a pharmacological substance administered in an inactive form. Once administered, the prodrug is metabolised in vivo into an active metabolite, a process termed bioactivation. The rationale behind the use of a prodrug is generally for absorption, distribution, metabolism, and...

 and it has no intrinsic antibacterial activity, but is converted by the body to ampicillin

Ampicillin

Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci...

, which is active against a variety of organisms.

Administration

Hetacillin is administered orally. The potassium salt, hetacillin potassium, is administered by injection

Injection (medicine)

An injection is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body...

, either intravenously or intramuscularly.

Hetacillin was removed from the market for human use when the discovery was made that it is actually cleaved in the GI tract to formaldehyde and had no benefit to non-ester derivatives (i.e. Ampicillin).