Ornidazole is an antiprotozoal, antibacterial agent. The nitro-group of ornidazole is reduced by cell extracts of Trichomonas. The free nitro-radical generated as aresult of this reduction may be responsible for the antiprotozoal activity. It caused DNA base changes in bacterial cells and DNA strand breakage in mammalian cells. Half-life is approximately 12-14 hours
Ornidazole is absorbed rapidly following oral administration; peak plasma concentrations usually attained after 2 hours.
Distributed virtually all body tissues and body fluids. Plasma protein binding of ornidazole is <15%
Ornidazole is mainly metabolized to 2-hydroxymethyl and a-hydroxymethyl metabolites in the liver. Both main metabolites are less active against Trichomonas vaginalis and anaerobic bacteria than the unchanged ornidazole
It is excreted in the urine mainly as conjugates and metabolites and to a lesser extent in the feaces.
Class: Antiprotozoal agent
It is indicated for the treatment of amoebiasis all intestinal infections due to Entamoeba histolytica, including amoebic dysentery. All extraintestinal forms of amoebiasis, especially amoebic liver abscesses, giardiasis, trichomoniasis, bacterial vaginosis (non-specific vaginitis); infections due to anaerobic bacteria; prevention of postoperative anaerobic infections.
It is contraindicated in patients with known hypersensitivity to the drug or to other nitroimidazole derivatives.
Special precautions and warnings
CNS: caution should be exercised in patients with diseases of the CNS, e.g. epilepsy or multiple sclerosis
Pregnancy and lactation: Pregnancy category C. It has not been shown to have any teratogenic or foetotoxic action, it is recommended not to use during pregnancy and lactation period except when necessary as no controlled studies have been carried out in pregnant women. It should be used only if a potential benefit justifies the potential risk to the fetus.
Renal impairment: Use with caution in patients with renal impairment
Hepatic impairment: Use with caution in patients with hepatic impairment
Dosage and directions for use
Amoebiasis: 500mg twice daily for 5-10 days. For patients >60kg body weight, 1g twice daily for 3 days
Giardiasis: 1-1.5g once daily for 1-2 days
Trichomoniasis: 1.5g as a single dose or 500mg twice daily for 5 days. Sexual partner should be simultaneously treated
Bacterial vaginosis: 1.5g once or 500mg once daily for 5-7 days
Anaerobic bacterial infections: Initiate oral therapy as soon as possible after I.V infusion. 500mg twice daily for 5 to 10 days
Prevention of postoperative anaerobic bacterial infections: 1.5g as single dose 12 hour before surgery then 500mg twice daily for 3-5 days postoperatively.
Amoebiasis: 25 mg/kg once daily for 5 to 10 days
Amoebic dysentery: 40mg/kg once daily for 3 days
Giardiasis: 30-40mg/kg for 2 days
Trichomoniasis: 25mg/kg as a single dose
Anaerobic bacterial infections: 10mg/kg twice daily for 5-10 days
Somnolence, headache, nausea, vomiting, dizziness, tremor, rigidity, poor coordination, seizures, tiredness, vertigo, temporary loss of consciousness and signs of sensory or mixed peripheral neuropathy, taste disturbances, abnormal liver function tests, skin reactions.
Ornidazole may potentiate effect of coumarin-type oral anticoagulants
Ornidazole prolongs the muscle-relaxant effect of vecuronium bromide
Concomitant use of ornidazole with phenobarbital or other enzyme inductors reduces the serum half-life of ornidazole. Mixed-function oxidase (cytochrome P450 Isoenzyme) enzyme inhibitors (e.g. cimetidine) prolong the serum half-life of ornidazole.
Symptoms: overdosage may cause exacerbation of all the pharmacological side effects of ornidazole.
Treatment: in the event of overdose, treatment is symptomatic and supportive. Specific antidote is unknown