Title: Cyclacillin
CAS Registry Number: 3485-14-1
CAS Name: (2S,5R,6R)-6-[[(1-Aminocyclohexyl)carbonyl]amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid
Additional Names: 6-(1-aminocyclohexanecarboxamido)penicillanic acid; (1-aminocyclohexyl)penicillin; ciclacillin
Manufacturers' Codes: Wy-4508
Trademarks: Calthor (Ayerst); Citosarin (Toyo Jozo); Cyclapen (Wyeth); Syngacillin (Wyeth); Ultracillin (Grenthal); Vastcillin (Takeda); Vatracin (Tobishi); Vipicil (Wyeth); Wyvital (Wyeth)
Molecular Formula: C15H23N3O4S
Molecular Weight: 341.43
Percent Composition: C 52.77%, H 6.79%, N 12.31%, O 18.74%, S 9.39%
Literature References: Semi-synthetic antibiotic related to penicillin. Prepn: Alburn et al., US 3194802; C. A. Robinson, J. J. Nescio, DE 1800698; eidem, US 3478018 (1965, 1969, 1969, all to Am. Home Prods.). Activity studies: Rosenman et al., Antimicrob. Agents Chemother. 1967, 590; Hopper et al., ibid. 597; Yurchenco et al., ibid. 602; Chemotherapy 15, 209 (1970). Metabolic studies: Poole, J. Pharm. Sci. 59, 1255 (1970); Tucker et al., Toxicol. Appl. Pharmacol. 19, 361 (1971). Physicochemical data: Alburn et al., Antimicrob. Agents Chemother. 1967, 586; Hou, Poole, J. Pharm. Sci. 58, 1510 (1969); Poole, Bahal, ibid. 59, 1265 (1970).
Properties: Crystals, mp 182-183° (anhydrate) (Hou, Poole); also reported as mp 156-158° (dec) (Alburn et al.). [a]D25 +268° (water). pK1, pK2 in water: 2.68, 7.50; in 50% dioxane: 4.16, 7.04. Stable in acid. Soly at 38°: about 29 mg/ml.
Melting point: mp 182-183° (anhydrate) (Hou, Poole); mp 156-158° (dec) (Alburn et al.)
pKa: pK1, pK2 in water: 2.68, 7.50; in 50% dioxane: 4.16, 7.04
Optical Rotation: [a]D25 +268° (water)
Therap-Cat: Antibacterial.
Keywords: Antibacterial (Antibiotics); ?Lactams; Penicillins.
Cyclamic Acid Cyclarbamate Cyclethrin Cyclexanone Cyclexedrine

Systematic (IUPAC) name
(2S,5R,6R)-6-{[(1-aminocyclohexyl)carbonyl]amino}- 3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane- 2-carboxylic acid
Clinical data
AHFS/ International Drug Names
Legal status  ?
Routes Oral
Pharmacokinetic data
Bioavailability Moderate
Protein binding <25%
CAS number 3485-14-1 YesY
ATC code None
PubChem CID 19003
DrugBank DB01000
ChemSpider 17941 YesY
UNII 72ZJ154X86 YesY
KEGG D01334 YesY
ChEBI CHEBI:31444 YesY
Chemical data
Formula C15H23N3O4S 
Mol. mass 341.425 g/mol
 N (what is this?)  (verify)

Ciclacillin (INN) or cyclacillin (USAN), trade names Cyclapen, Cyclapen-W, Vastcillin, and others, is an aminopenicillin antibiotic. Its spectrum of activity is similar to that of ampicillin, although it is less susceptible to beta-lactamases than ampicillin and has much higher bioavailability.[1] A large randomized, double-blind clinical trial published in 1978 also showed that ciclacillin is associated with significantly fewer and milder adverse effects than ampicillin;[2] later studies seemed to confirm this improved tolerability, at least in children.[3][4]

Ciclacillin has been superseded by newer antibiotics and is no longer in clinical use, at least in the United States.[5]