Chemical formula: C₇H₁₀ClN₃O₃ Molecular mass: 219.63 g/mol PubChem compound: 28061
Ornidazole is effective against Trichomonas vaginalis, Entamoeba histolytica and Giardia lamblia (Giardia intestinalis), and also against certain anaerobic bacteria such as Bacteroides and Clostridium spp., Fusobacterium spp., and anaerobic cocci.
Following oral administration ornidazole is rapidly absorbed. Mean absorption is 90%. Peak plasma concentrations are reached within three hours.
The mean volume of distribution after i.v. administration is 1 litre per kg. Plasma protein binding of ornidazole is about 13%. Ornidazole penetrates the cerebrospinal fluid, the body fluids and the tissues very effectively.
Plasma concentrations are within the range considered to be optimal for the various indications (6 to 36 mg/l).
After repeated administration of 500 mg or 1000 mg every twelve hours to healthy volunteers, an accumulation factor of 1.5-2.5 was calculated.
Ornidazole is mainly metabolised 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.
The half-life is about thirteen hours. 85% of a single dose is eliminated within the first five days, most of this being metabolised. 4% of the dose is excreted as unaltered substance in the urine.
In patients with liver cirrhosis the elimination half-life is longer (22 versus 14 hours) and clearance lower (35 versus 51 ml/min) than in healthy subjects. The dosing interval should be doubled in patients with severe hepatic impairment.
The pharmacokinetics of ornidazole are unaltered in renal impairment. Dose adjustment is therefore unnecessary in patients with impaired renal function. Ornidazole is removed by haemodialysis. An additional dose of 500 mg of ornidazole should be administered if the daily dose is 2 g/day, or an additional dose of 250 mg ornidazole if the daily dose is 1 g/day, should therefore be administered before the start of haemodialysis.
The pharmacokinetics or ornidazole in neonates and young children are similar to those in adults.
None.
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