Ofloxacin 200 mg, Tinidazole 600 mg Tablets

Mechanism of Action — Tinidazole is an antiprotozoal,antibacterial agent. 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 Giardiaand Entamoebaspecies is not known.

Absorption — After oral administration, tinidazole is rapidly and completely absorbed. A bioavailability study of tinidazole tablets was conducted in adult healthy volunteers. All subjects received a single oral dose of 2 g (four 500 mg tablets) of tinidazole tablets following an overnight fast. Oral administration of four 500 mg tablets of tinidazole tablets under fasted conditions produced a mean peak plasma concentration (C max) of 47.7 (±7.5) μg/mL with a mean time to peak concentration (T max) of 1.6 (±0.7) hours, and a mean area under the plasma concentration-time curve (AUC 0 to ∞) of 901.6 (± 126.5) μg hr/mL at 72 hours. The elimination half-life (T 1/2) was 13.2 (±1.4) hours. Mean plasma levels decreased to 14.3 μg/mL at 24 hours, 3.8 μg/mL at 48 hours and 0.8 μg/mL at 72 hours following administration. Steady-state conditions are reached in 2½ to 3 days of multi-day dosing.

Administration of tinidazole tablets with food resulted in a delay in T maxof approximately 2 hours and a decline in C maxof approximately 10%, compared to fasted conditions. However, administration of tinidazole tablets with food did not affect AUC or T 1/2in this study.

In healthy volunteers, administration of crushed tinidazole tablets in artificial cherry syrup, [prepared as described in Dosage and Administration (2.2) ] after an overnight fast had no effect on any pharmacokinetic parameter as compared to tablets swallowed whole under fasted conditions.

Distribution — Tinidazole is distributed into virtually all tissues and body fluids and also crosses the blood-brain barrier. The apparent volume of distribution is about 50 liters. Plasma protein binding of tinidazole is 12%.

Elimination — The plasma half-life of tinidazole is approximately 12 to 14 hours.

Metabolism:Tinidazole is significantly metabolized in humans prior to excretion. Tinidazole is partly metabolized by oxidation, hydroxylation, and conjugation. Tinidazole is the major drug-related constituent in plasma after human treatment, along with a small amount of the 2-hydroxymethyl metabolite. Tinidazole is biotransformed mainly by CYP3A4. In an in vitrometabolic drug interaction study, tinidazole concentrations of up to 75 μg/mL did not inhibit the enzyme activities of CYP1A2, CYP2B6, CYP2C9, CYP2D6, CYP2E1, and CYP3A4. The potential of tinidazole to induce the metabolism of other drugs has not been evaluated.

Excretion:Tinidazole is excreted by the liver and the kidneys. Tinidazole is excreted in the urine mainly as unchanged drug (approximately 20-25% of the administered dose). Approximately 12% of the drug is excreted in the feces.

Specific Populations — Patients with impaired renal function: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. Approximately 43% of the amount present in the body is eliminated during a 6-hour hemodialysis session [See Use in Specific Populations (8.6)] . The pharmacokinetics of tinidazole in patients undergoing routine continuous peritoneal dialysis have not been investigated.

Patients with impaired hepatic function:There are 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 [See Use in Specific Populations (8.7)] .

Following oral administration, the bioavailability of ofloxacin in the tablet formulation is approximately 98%. Maximum serum concentrations are achieved one to two hours after an oral dose. Absorption of ofloxacin after single or multiple doses of 200 to 400 mg is predictable, and the amount of drug absorbed increases proportionately with the dose. Ofloxacin has biphasic elimination. Following multiple oral doses at steady-state administration, the half-lives are approximately 4 to 5 hours and 20 to 25 hours. However, the longer half-life represents less than 5% of the total AUC. Accumulation at steady-state can be estimated using a half-life of 9 hours. The total clearance and volume of distribution are approximately similar after single or multiple doses. Elimination is mainly by renal excretion. The following are mean peak serum concentrations in healthy 70 to 80 kg male volunteers after single oral doses of 200, 300, or 400 mg of ofloxacin or after multiple oral doses of 400 mg.

Steady-state concentrations were attained after four oral doses, and the area under the curve (AUC) was approximately 40% higher than the AUC after single doses. Therefore, after multiple-dose administration of 200 mg and 300 mg doses, peak serum levels of 2.2 mcg/mL and 3.6 mcg/mL, respectively, are predicted at steady-state.

In vitro, approximately 32% of the drug in plasma is protein bound.

The single dose and steady-state plasma profiles of ofloxacin injection were comparable in extent of exposure (AUC) to those of ofloxacin tablets when the injectable and tablet formulations of ofloxacin were administered in equal doses (mg/mg) to the same group of subjects. The mean steady-state AUC(0 to 12) attained after the intravenous administration of 400 mg over 60 min was 43.5 mcg•h/mL; the mean steady-state AUC(0 to 12) attained after the oral administration of 400 mg was 41.2 mcg•h/mL (two one-sided t-test, 90% confidence interval was 103 to 109). (see following chart).

Between 0 and 6 h following the administration of a single 200 mg oral dose of ofloxacin to 12 healthy volunteers, the average urine ofloxacin concentration was approximately 220 mcg/mL. Between 12 and 24 hours after administration, the average urine ofloxacin level was approximately 34 mcg/mL.

Following oral administration of recommended therapeutic doses, ofloxacin has been detected in blister fluid, cervix, lung tissue, ovary, prostatic fluid, prostatic tissue, skin, and sputum. The mean concentration of ofloxacin in each of these various body fluids and tissues after one or more doses was 0.8 to 1.5 times the concurrent plasma level. Inadequate data are presently available on the distribution or levels of ofloxacin in the cerebrospinal fluid or brain tissue.

Ofloxacin has a pyridobenzoxazine ring that appears to decrease the extent of parent compound metabolism. Between 65% and 80% of an administered oral dose of ofloxacin is excreted unchanged via the kidneys within 48 hours of dosing. Studies indicate that less than 5% of an administered dose is recovered in the urine as the desmethyl or N-oxide metabolites. Four to eight percent of an ofloxacin dose is excreted in the feces. This indicates a small degree of biliary excretion of ofloxacin.

The administration of ofloxacin tablets with food does not affect the Cmax and AUC∞ of the drug, but Tmax is prolonged.

Clearance of ofloxacin is reduced in patients with impaired renal function (creatinine clearance rate < 50 mL/min), and dosage adjustment is necessary. (see PRECAUTIONS, General and DOSAGE AND ADMINISTRATION ).

Following oral administration to healthy elderly subjects (65 to 81 years of age), maximum plasma concentrations are usually achieved one to two hours after single and multiple twice-daily doses, indicating that the rate of oral absorption is unaffected by age or gender. Mean peak plasma concentrations in elderly subjects were 9 to 21% higher than those observed in younger subjects. Gender differences in the pharmacokinetic properties of elderly subjects have been observed. Peak plasma concentrations were 114% and 54% higher in elderly females compared to elderly males following single and multiple twice-daily doses. [This interpretation was based on study results collected from two separate studies.] Plasma concentrations increase dose-dependently with the increase in doses after single oral dose and at steady state. No differences were observed in the volume of distribution values between elderly and younger subjects. As in younger subjects, elimination is mainly by renal excretion as unchanged drug in elderly subjects, although less drug is recovered from renal excretion in elderly subjects. Consistent with younger subjects, less than 5% of an administered dose was recovered in the urine as the desmethyl and N-oxide metabolites in the elderly. A longer plasma half-life of approximately 6.4 to 7.4 hours was observed in elderly subjects, compared with 4 to 5 hours for young subjects. Slower elimination of ofloxacin is observed in elderly subjects as compared with younger subjects which may be attributable to the reduced renal function and renal clearance observed in the elderly subjects. Because ofloxacin is known to be substantially excreted by the kidney, and elderly patients are more likely to have decreased renal function, dosage adjustment is necessary for elderly patients with impaired renal function as recommended for all patients. (see PRECAUTIONS, General and DOSAGE AND ADMINISTRATION ).

Ofloxacin is a quinolone antimicrobial agent. The mechanism of action of ofloxacin and other fluoroquinolone antimicrobials involves inhibition of bacterial topoisomerase IV and DNA gyrase (both of which are type II topoisomerases), enzymes required for DNA replication, transcription, repair and recombination.