N,N-bis(2-chloroethyl)-1,3,2-oxazaphosphinan-2-amine 2-oxide

Absorption
Well absorbed orally. T max is 2 to 3 h for metabolites (IV dose).

Distribution
More than 75% bioavailable after oral administration. More than 60% of metabolites are bound to plasma proteins. Low protein binding for cyclophosphamide.

Metabolism
Converted to active alkylating metabolites in the liver.

Elimination
The t ½ is 3 to 12 h (unchanged drug). Eliminated primarily as metabolites. 5% to 25% is excreted in urine as unchanged drug.

Special Populations
Renal Function Impairment
Metabolites may be elevated but increased toxicity has not been seen.

Anticoagulants
Increased hypoprothrombinemic effect may occur.

Barbiturates, other enzyme inducers
May increase the rate of active cyclophosphamide metabolite formation and possibly increase neutropenic effects.

Chloramphenicol, other enzyme inhibitors
May inhibit cyclophosphamide's antineoplastic activity by decreasing rate of active metabolite formation.

Digoxin
May cause decreased serum levels of digoxin.

Oral quinolone antibiotics
May cause decreased GI absorption of quinolone antibiotics.

Succinylcholine and possibly mivacurium
Prolongation of neuromuscular blockade by cyclophosphamide's inhibition of pseudocholinesterase may occur.