Ornidazole

(USAN, rINN)
Ornidazole Chemical formula
Synonyms: Ornidatsoli; Ornidazol; Ornidazolum; Ro-7-0207. 1-Chloro-3(2-methyl-5-nitroimidazol-1-yl)propan-2-ol.
Cyrillic synonym: Орнидазол.

💊 Chemical information

Chemical formula: C7H10ClN3O3 = 219.6.
CAS — 16773-42-5.
ATC — G01AF06; J01XD03; P01AB03.
ATC Vet — QG01AF06; QJ01XD03; QP51AA03.

💊 Adverse Effects and Precautions

As for Metronidazole.

💊 Pharmacokinetics

Ornidazole is readily absorbed from the gastrointestinal tract and peak plasma concentrations are reached within 3 hours. After repeated oral doses of 500 mg every 12 hours, steady-state peak and trough concentrations are 14 and 6 micrograms/mL respectively. The plasma elimination half-life of ornidazole is 12 to 14 hours. Less than 15% is bound to plasma proteins. It is widely distributed in body tissues and fluids, including the CSF. Ornidazole is metabolised in the liver and is excreted in the urine, mainly as conjugates and metabolites, and to a lesser extent in the faeces. Biliary excretion may be important in the elimination of ornidazole and its metabolites.
1. Schwartz DE, Jeunet F. Comparative pharmacokinetic studies of ornidazole and metronidazole in man. Chemotherapy 1976; 22: 19–29
2. Matheson I, et al. Plasma levels after a single oral dose of 1.5 g ornidazole. Br J Vener Dis 1977; 53: 236–9
3. Schwartz DE, et al. Metabolic studies of ornidazole in the rat, in the dog and in man. Xenobiotica 1979; 9: 571–81
4. Turcant A, et al. Pharmacokinetics of ornidazole in neonates and infants after a single intravenous infusion. Eur J Clin Pharmacol 1987; 32: 111–13
5. Martin C, et al. Pharmacokinetics and tissue penetration of a single dose of ornidazole (1,000 milligrams intravenously) for antibiotic prophylaxis in colorectal surgery. Antimicrob Agents Chemother 1990; 34: 1921–4
6. Bourget P, et al. Disposition of ornidazole and its metabolites during pregnancy. J Antimicrob Chemother 1995; 35: 691–6.

Hepatic impairment.

The elimination of ornidazole after a single intravenous dose of 500 mg was impaired in 10 patients with severe liver cirrhosis when compared with 10 healthy subjects; mean half-lives were 21.9 hours and 14.1 hours respectively.1 These results suggested that the interval between doses of ornidazole should be doubled in patients with marked hepatic impairment. The need for dose adjustment was confirmed in further studies of patients with other forms of liver disease.2,3
1. Taburet AM, et al. Pharmacokinetics of ornidazole in patients with severe liver cirrhosis. Clin Pharmacol Ther 1986; 40: 359–64
2. Bourget P, et al. Ornidazole pharmacokinetics in several hepatic diseases. J Pharmacol Clin 1988; 7: 25–32
3. Taburet AM, et al. Pharmacokinetics of ornidazole in patients with acute viral hepatitis, alcoholic cirrhosis, and extrahepatic cholestasis. Clin Pharmacol Ther 1989; 45: 373–9.

Renal impairment.

The half-life of intravenous ornidazole was not prolonged in a study in patients with advanced chronic renal failure, including those on continuous ambulatory peritoneal dialysis, although total plasma clearance was halved; modification of the usual dosage is not necessary in such patients. However, the drug was removed by haemodialysis and ornidazole should be given after the dialysis session rather than before.1In another study2 the systemic availability and total body clearance of ornidazole were unaffected in chronic renal failure; it was considered that an additional dose should be given before haemodialysis to compensate for removal during that procedure.
1. Merdjan H, et al. Pharmacokinetics of ornidazole in patients with renal insufficiency; influence of haemodialysis and peritoneal dialysis. Br J Clin Pharmacol 1985; 19: 211–17
2. Horber FF, et al. High haemodialysis clearance of ornidazole in the presence of a negligible renal clearance. Eur J Clin Pharmacol 1989; 36: 389–93.

💊 Uses and Administration

Ornidazole is a 5-nitroimidazole derivative. It has the antimicrobial actions of metronidazole and is used similarly in the treatment of susceptible protozoal infections and also in the treatment and prophylaxis of anaerobic bacterial infections. It is given orally after food, or intravenously. Intravenous solutions of ornidazole should be diluted to 5 mg or less per mL and 100 or 200 mL infused over 15 to 30 minutes. In amoebiasis, 500 mg of ornidazole is given orally twice daily for 5 to 10 days; children are given 25 mg/kg as a single daily dose for 5 to 10 days. Patients with amoebic dysentery may be given 1.5 g as a single daily dose for 3 days; the children’s dose is 40 mg/kg daily. An alternative regimen for adults over 60 kg is 1 g twice daily for 3 days. In severe amoebic dysentery and amoebic liver abscess, ornidazole may be given by intravenous infusion in a dose of 0.5 to 1 g initially, followed by 500 mg every 12 hours for 3 to 6 days; the children’s dose is 20 to 30 mg/kg daily. In giardiasis, 1 or 1.5 g of ornidazole is given orally as a single daily dose for 1 or 2 days; the children’s dose is 30 or 40 mg/kg daily. In trichomoniasis, a single oral dose of 1.5 g is given; alternatively, a 5-day oral course of ornidazole 500 mg twice daily may be used. Sexual partners should also be treated. The children’s dose is 25 mg/kg as a single dose by mouth. For the treatment of anaerobic bacterial infections, ornidazole is given by intravenous infusion in an initial dose of 0.5 to 1 g, followed by 1 g daily as a single dose or in two divided doses for 5 to 10 days; oral therapy with 500 mg every 12 hours should be substituted as soon as possible. Children may be given 10 mg/kg intravenously every 12 hours for 5 to 10 days. For the prevention of postoperative anaerobic bacterial infections, 1 g is given by intravenous infusion about 30 minutes before surgery.

Administration in hepatic impairment.

In view of the prolonged half-life and reduced clearance of ornidazole reported in patients with hepatic dysfunction (see above), the interval between doses should be doubled in patients with severe hepatic impairment.

Administration in renal impairment.

The elimination of ornidazole is reported to be largely unaltered in patients with impaired renal function (see under Pharmacokinetics, above). Dosage adjustment is therefore usually unnecessary, although patients receiving haemodialysis should be given a supplemental dose of ornidazole before dialysis; a supplemental dose of 500 mg should be given if the daily dose is 2 g daily or 250 mg should be given if the daily dose is 1 g daily.

💊 Preparations

Proprietary Preparations

Arg.: Mebaxol; Belg.: Tiberal; Chile: Invigan; Cz.: Avrazor; Fr.: Tiberal; Gr.: Betiral†; India: Giro; Oniz; Ornida; Zil; Mex.: Danubial†; NZ: Tiberal; Rus.: Dazolic (Дазолик); Ornisid (Орнисид); Spain: Tinerol†; Switz.: Tiberal; Turk.: Biteral; Borneral; Ornidone; Ornisid; Ornitop; Venez.: Tiberal†. Multi-ingredient: India: Bidoflox-Oz†; Gatiquin Oz Kit; Levoflox Oz Kit; Ocimix; Orflaz Kit; Ornof; Tariflox Plus.
Published December 13, 2018.