The pharmacokinetic behaviour of hypoxoside taken orally by patients with lung cancer in a phase I trial

• Published in: SAMJ. South African medical journal Vol. 85; no. 9; pp. 861 - 865
• Main Authors: ALBRECHT, C. F, KRUGER, P. B, SMIT, B. J, FREESTONE, M, GOUWS, L, MILLER, R, VAN JAARSVELD, P. P
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Pinelands Medical Association of South Africa 01-09-1995
• Subjects: Adult; Aged; Alkynes - administration & dosage; Alkynes - pharmacokinetics; Alkynes - therapeutic use; Antineoplastic agents; Antineoplastic Agents - administration & dosage; Antineoplastic Agents - pharmacokinetics; Antineoplastic Agents - therapeutic use; Biological and medical sciences; Chemotherapy; Glucosides - administration & dosage; Glucosides - pharmacokinetics; Glucosides - therapeutic use; Humans; Lung Diseases - drug therapy; Lung Diseases - pathology; Lung Neoplasms - drug therapy; Lung Neoplasms - pathology; Medical sciences; Middle Aged; Pharmacology. Drug treatments; Tropical medicine; South Africa; Africa; Antineoplastic agent; Human; Lung disease; Monocotyledones; Respiratory disease; Hypoxidaceae; Lung; Prodrug; Malignant tumor; Chemotherapy; Treatment; Angiospermae; Phase I trial; Spermatophyta; Pharmacokinetics
• ISSN: 0256-9574

To study the pharmacokinetic behaviour of hypoxoside taken orally by 24 patients with lung cancer.
Randomised open study with three single doses of 1,600, 2,400 and 3,200 mg standardised Hypoxis plant extract (200 mg capsules) and a multiple-dose study on the first 6 patients taking 4 capsules 3 times daily for 11 days.
Patients with histologically proven squamous, large-cell or adenocarcinoma were hospitalised at the Radiation Oncology Ward, Karl Bremer Hospital, Bellville, W. Cape.
Blood was drawn at regular intervals up to 75 hours after single doses and the concentrations of metabolites of the aglucone of hypoxoside, rooperol, were measured with a high-performance liquid chromatography method. For the multiple-dose study blood was drawn before the first dose each day. Concentration-time relationships were analysed according to a conventional single open-compartment model and also by using the NONMEM digital computer programme.
Neither hypoxoside nor rooperol appear in circulation. This is due to complete phase II biotransformation to diglucuronide, disulphate and mixed glucuronide-sulphate metabolites, of which the latter is the major component. Considerable interpatient variation in concentration-time relationships was found in the single-dose studies. It was due to an active enterohepatic recirculation in some patients and a distinct lag phase in others together with zero-order rate of formation of rooperol in the colon. Computer modelling indicated a single open-compartment model in which the mass of the patient did not influence volume of distribution and clearance because formation of the metabolites is dependent on the metabolising capacity of the patient. However, the elimination of the metabolites follows first-order kinetics with half-lives ranging from 50 hours for the major metabolite to 20 hours for the two minor metabolites. Multiple-dose studies also showed large interpatient variation.
In order to reach metabolite levels near 100 micrograms/ml, which have been shown to be tumouricidal after enzymatic deconjugation to rooperol, maintenance doses need to be individualised for each patient. For most patients, however, a daily dose of 2,400 mg was sufficient.