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Clinical pharmacology of isophosphamide
Author(s) -
Creaven Patrick J.,
Allen Larry M.,
Alford Dorothy A.,
Cohen Martin H.
Publication year - 1974
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1002/cpt1974161part177
Subject(s) - urine , chemistry , urinary system , pharmacology , cyclophosphamide , excretion , endocrinology , medicine , chemotherapy , biochemistry
The alkylating activity in the urine was measured in patients receiving a new antineoplastic cyclophosphomide analog, isophosphamide (IP), at doses of 2,900 to 5,000 mg per square meter body surface area (BSA) and compared with that of patients receiving 1,100 mg per square meter of cyclophosphamide (CP). Total excretion of alkylating activity after CP (1,l00 mg per square meter) lay between values for the 3,800 mg per square meter dose and the 5,000 mg per square meter dose of IP. The concentration of urinary alkylating activity was higher in patients who developed cystitis than in those who did not. Alkylating activity in the urine was unaltered by acetylcysteine bladder washout. Plasma alkylating activity was more persistent after 5,000 mg per square meter IP than after 1,100 mg per square meter CPo After [HC] IP 5,000 mg per square meter, the plasma half‐life was 13.79 hours, and the urinary recovery of radioactivity was 81.6%, of which 61.6% was unchanged drug. These values differ markedly from those published for CPo IP penetrated the blood‐brain barrier, but its metabolites did not. The greater propensity of IP than of CP to cause cystitis at apprOXimately equitoxic doses may be related to larger amounts of alkylating activity in urine of patients receiving IP. The greater dose of IP than of CP required to produce the same alkylating activity in urine correlates well with the differences in Km of the two drugs in an isolated microsomal enzyme system in vitro previously reported.