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Hetacillin structure.svg
Systematic (IUPAC) name
(2S,5R,6R)-6-[(4R)-2,2-dimethyl-5-oxo-4-phenylimidazolidin-1-yl]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid
Clinical data
Trade names Hetacin
AHFS/Drugs.com Veterinary Use
Legal status
Routes of
Intramammary injection
CAS Number 3511-16-8 YesY
ATC code J01CA18
PubChem CID: 193260
DrugBank DB00739 YesY
ChemSpider 167708 YesY
KEGG D01074 N
Chemical data
Formula C19H23N3O4S
Molecular mass 389.469 g/mol
 N (what is this?)  (verify)

Hetacillin is a beta-lactam antibiotic that is part of the aminopenicillin family. It is a prodrug and it has no antibacterial activity itself,[1] but quickly splits of acetone in the human body to form ampicillin,[2] which is active against a variety of bacteria.


Hetacillin can be administered orally.[2] The potassium salt, hetacillin potassium, is administered by injection, either intravenously or intramuscularly.[citation needed] It is sold under the trade name Hetacin for intramammary injection in veterinary use.[3]

Hetacillin was removed from the market for human use when the discovery was made that it is actually cleaved in the gastrointestinal tract to formaldehyde and had no advantages over ampicillin.[citation needed]


Hetacillin is prepared from ampicillin and acetone. In aqueous solutions it is unstable, with a half life of 15 to 30 minutes at 37 °C (99 °F) and pH 7, quickly releasing acetone again.[1][4]

As opposed to ampicillin, hetacillin is only marginally broken down by the bacterial enzyme beta-lactamase, at least in vitro.[4]


  1. ^ a b Drugbank: Hetacillin
  2. ^ a b Sutherland, R.; Robinson, O. P. (1967). "Laboratory and pharmacological studies in man with hetacillin and ampicillin". British Medical Journal 2 (5555): 804–808. doi:10.1136/bmj.2.5555.804. PMC 1843140. PMID 5182358. 
  3. ^ Hetacin-K Intramammary Infusion for Veterinary Use
  4. ^ a b Faine, S.; Harper, M. (1973). "Independent antibiotic actions of hetacillin and ampicillin revealed by fast methods". Antimicrobial agents and chemotherapy 3 (1): 15–18. doi:10.1128/aac.3.1.15. PMC 444353. PMID 4597707.