Use of ornidazole in fractionated radiotherapy: dose tolerance, serum and tumour tissue concentration.

Sensitizing and neurotoxic effect of ornidazole, was tested in a double-blind randomized study in patients with carcinoma of the cervix and larynx. Ornidazole or placebo were given orally, two times weekly, for 3 weeks. Dose was 2.5 g/m2 for each administration. Total dose given was 15 g/m2. Radiation therapy was given 3 h after the drug administration. Ornidazole was well tolerated in the majority of the patients. No neurotoxic side effects, such as peripheral neuropathy or convulsion, were observed with a total dose of up to 30 g. Dizziness, somnolence and nausea were the prominent acute side effects, seen mostly (70%) in women. In the placebo group this rate was 17% (p less than 0.01). No important side effect was observed in men receiving ornidazole. Serum concentration of ornidazole reached the maximum level in 2-4 h after oral administration and ranged (23 patients) from 65.1 to 139.8 micrograms/ml. Mean half-life was 15.6 +/- 2.8 h. Peak concentration in tumour tissue was achieved 1-3 h after the administration, ranging from 13.0 to 78.0 micrograms/g. Tumour concentration of ornidazole ranged from 14 to 93% of the serum concentration at the time of irradiation.