Clinical Pharmacology

Tindamax^® contains tinidazole, a synthetic antiprotozoal and antibacterial agent with a proven efficacy and safety profile. Tinidazole, a second generation nitroimidazole, is chemically related to metronidazole, a first-generation nitroimidazole. However, tinidazole is a different molecule, has a different half-life and requires different dosing regimens.

Pharmacokinetics of tinidazole

• After oral administration, tinidazole is rapidly and completely absorbed.
• Tinidazole is distributed into virtually all tissues and body fluids and also crosses the blood-brain barrier.
• Tinidazole is significantly metabolized in humans prior to excretion.
• The plasma half-life of tinidazole is approximately 12-14 hours.
• The pharmacokinetics of tinidazole in patients with severe renal impairment (CrCL < 22 mL/min) are not significantly different from the pharmacokinetics seen in healthy subjects. However, during hemodialysis, clearance of tinidazole is significantly increased; the half-life is reduced from 12.0 hours to 4.9 hours.
• There is no data on tinidazole pharmacokinetics in patients with impaired hepatic function. Reduction of metabolic elimination of metronidazole, a chemically-related nitroimidazole, in patients with hepatic dysfunction has been reported in several studies.

Microbiology of tinidazole

Mechanism of action

The nitro- group of tinidazole is reduced by cell extracts of Trichomonas. The free nitro- radical generated as a result of this reduction may be responsible for the antiprotozoal activity. Chemically reduced tinidazole was shown to release nitrites and cause damage to purified bacterial DNA in vitro. Additionally, the drug caused DNA base changes in bacterial cells and DNA strand breakage in mammalian cells.

The mechanism by which tinidazole exhibits activity against Giardia and Entamoeba species is not known.

Antibacterial

Tinidazole is active in vitro against most strains of the following organisms that have been reported to be associated with bacterial vaginosis:

• Bacteroides spp.
• Gardnerella vaginalis
• Prevotella spp.

Tinidazole does not appear to have activity against most strains of vaginal lactobacilli.

Antiprotozoal

Tinidazole demonstrates activity both in vitro and in clinical infections against the following protozoa:

• Trichomonas vaginalis
• Giardia lamblia (also termed G. duodenalis)
• Entamoeba histolytica

Drug resistance

The development of resistance to tinidazole by G. duodenalis, E. histolytica, or bacteria associated with bacterial vaginosis has not been examined.

Cross-resistance

Approximately 38% of T. vaginalis isolates exhibiting reduced susceptibility to metronidazole also show reduced susceptibility to tinidazole in vitro. The clinical significance of such an effect is not known.