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Not to be confused with penam.

A penem is a type of β-lactam with an unsaturated five-member heterocycle containing a sulfur atom in a pentacyclic ring fused to the β-lactam ring. Penems do not occur naturally; all are synthetic.[1] Related to penems are carbapenems, which have a carbon atom in place of the sulfur atom.[2]

An example is faropenem.[3]

Structure

See also: β-Lactam nomenclature
Faropenem, a penem. A sulfur atom and a double bond are present in the pentacyclic ring.[4]
Imipenem, a carbapenem. Imipenem has a sulfur atom that is not in the pentacyclic ring.
Benzylpenicillin, a penicillin. The double bond is absent in the pentacyclic ring.

Penem molecules do not occur naturally, and production of penems is an entirely synthetic process.[5]

Five main penem subgroups — thiopenems, oxypenems, aminopenems, alkylpenems, and arylpenems — have been produced and are distinguished by the side chain (at position 2) of the unsaturated five-membered ring.[5] One structurally distinct penem is BRL 42715. This molecule has no substitution at the above position, but has a bulky group attached to the β-lactam ring, and it displays effective inhibition of class C β-lactamases, but no antimicrobial activity.[6]

One possible consequence of these structural differences of penems from other β-lactams may be reduced immunogenicity and immunogenic cross-reactivity.[citation needed]

References

  1. ^ Richard Wise (1990). “The carbapenems and Penem Antibiotics—a brief review”. Antimicrobic Newsletter. 7 (10): 73–78. doi:10.1016/0738-1751(90)90045-E.
  2. ^ “Medscape.com”.
  3. ^ Milazzo I, Blandino G, Caccamo F, Musumeci R, Nicoletti G, Speciale A (March 2003). “Faropenem, a new oral penem: antibacterial activity against selected anaerobic and fastidious periodontal isolates”. Journal of Antimicrobial Chemotherapy. 51 (3): 721–5. doi:10.1093/jac/dkg120. PMID 12615878.
  4. ^ Schurek, Kristen N.; Wiebe, Ryan; Karlowsky, James A.; Rubinstein, Ethan; Hoban, Daryl J.; Zhanel, George G. (2007). “Faropenem: Review of a new oral penem”. Expert Review of Anti-Infective Therapy. 5 (2): 185–198. doi:10.1586/14787210.5.2.185. PMID 17402834.
  5. ^ a b Rusu, Aura; Oancea, Octavia-Laura; Donici, Elena; Uncu, Livia (2025-05-11). “Recent Developments in Penem Antibiotics: Structural and Therapeutic Perspectives”. Molecules (Basel, Switzerland). 30 (10): 2126. doi:10.3390/molecules30102126. ISSN 1420-3049. PMC 12113772. PMID 40430299.
  6. ^ Coleman, K.; Griffin, D. R.; Page, J. W.; Upshon, P. A. (September 1989). “In vitro evaluation of BRL 42715, a novel beta-lactamase inhibitor”. Antimicrobial Agents and Chemotherapy. 33 (9): 1580–1587. doi:10.1128/AAC.33.9.1580. ISSN 0066-4804. PMC 172706. PMID 2817854.

Further reading