Synthesis, characterization and evaluation of tinidazole-loaded mPEG-PDLLA (10/90) in situ gel forming system for periodontitis treatment.

Traditional in situ gel forming systems are potential applications for parenteral administration but always accompanied with burst release. To overcome this limitation, the tinidazole (TNZ)-loaded in situ gel forming system using a diblock copolymer, monomethoxy poly(ethylene glycol)-block-poly(d,l-lactide) (mPEG-PDLLA), was designed. The formulation of the mPEG-PDLLA-based TNZ in situ gel forming system contained 5% (w/w) TNZ, 0.4% glycerol, 5 ml N-methyl pyrrolidone (NMP) and 35% (w/w) mPEG-PDLLA. The in situ gel forming system showed sustained TNZ release over 192 h with low burst effect (around 7% in the first 8 h) in the in vitro release study. Additionally, in vivo studies were performed on rabbits with ligature-induced periodontitis, and the concentration of TNZ in the gingival crevicular fluid (GCF) as well as the pharmacokinetic parameters was calculated and the pharmacological effect of TNZ-loaded in situ gel forming (mPEG-PDLLA)-based system was found effective. Finally, histological studies revealed that the gel was a safe formulation with low irritation. The desirable drug release kinetics combined with the excellent in vivo characteristics highlight the potential of the gel in the treatment of periodontitis. Therefore, these results confirmed that the TNZ-loaded in situ gel forming mPEG-PDLLA-based system could reduce burst release of TNZ and act as a sustained-release and injectable drug depot for periodontitis treatment.

Multiple targeted drugs carrying biodegradable membrane barrier: anti-adhesion, hemostasis, and anti-infection.

A multiple targeted drug carrying bilayer membrane for preventing an abdominal adhesion is prepared by electrospinning. Two bioactive drugs were successfully incorporated into this bilayer membrane and can be independently released from nanofibrous scaffolds without losing structural integrity and functionality of the anti-adhesion membrane. Besides, the drug release profile could be easily adjusted by optimizing the swelling behavior of the fibrous scaffold. The inner layer of the bilayered fibrous membranes loaded with carbazochrome sodium sulfonate (CA) showed an excellent vascular hemostatic efficacy and formed little clot during in vivo experiment. The outer layer loaded with tinidazole (TI) had outstanding antibacterial effect against the anaerobe. We believe this approach could serve as a model technique to guide the design of implants with drug delivery functions.

Concentrations of tinidazole in gingival crevicular fluid and plasma in dogs after multiple dose administration.

Tinidazole 15 mg/kg was administered to eight Beagle dogs with gingivitis or periodontitis twice daily for 3 days. Tinidazole concentrations in blood and gingival crevicular fluid (GCF) were measured 1, 3, 6 and 9 h after the morning dose each day. The concentration of tinidazole was determined by high performance liquid chromatography (HPLC). The mean concentration of tinidazole in GCF for each dog ranged from 6.05 to 9.32 micrograms/mL at different time points after the first dose, and on the first day the highest concentration was observed 6 h after the drug administration. Tinidazole concentrations were 34 +/- 4%-72 +/- 9% (mean +/- SEM) of simultaneous plasma concentration. At steady-state, on the third treatment day, the mean tinidazole concentrations in GCF ranged from 6.68 to 13.1 micrograms/mL, i.e. 44 +/- 6%-75 +/- 25% of the corresponding concentrations in plasma. Tinidazole concentration in GCF exceeded the MIC values for putative path-ogenic periodontal bacteria and it is concluded that, when indicated, tinidazole could be used for chemotherapy of periodontitis in dogs.

Rapid and selective high-performance liquid chromatographic method for the determination of metronidazole and its active metabolite in human plasma, saliva and gastric juice.

A rapid and selective HPLC method has been developed for the separation and quantitation of metronidazole and its hydroxylated metabolite in human plasma, saliva and gastric juice. The assay requires a simple protein precipitation step prior to analysis and is selective, sensitive and reproducible. The limits of quantitation (0.5-ml sample) were at least 0.25 microgram/ml for metronidazole and 0.20 micrograms/ml for its hydroxy metabolite. A Hypersil ODS 5 micron (150 x 4.5 mm I.D.) column was used with a mobile phase of acetonitrile-aqueous 0.05 M potassium phosphate buffer (pH 7) containing 0.1 % triethylamine (10:90) delivered at a flow-rate of 1.0 ml/min.

Bacterial mutagens in the urine of patients under tinidazole treatment.

Tinidazole is an antiparasitic drug belonging to the 5-nitroimidazole family. It is prescribed against protozoal infestations and is widely used in Mexico as well as other underdeveloped countries where infectious diseases are the first cause of children mortality. The drug is a direct mutagen in Salmonella typhimurium TA100 strain and the presence of S9 mixture did not modify its mutagenic effect. At low doses no mutagenicity was detected with strains TA100NR, TA98 or UTH8414 (Uvr+ derivative of TA100). Urine from four patients under tinidazole treatment exhibited a mutagenic activity on strain TA100, greater than the expected from the tinidazole concentrations determined by high-performance liquid chromatography (HPLC). Components from the urine samples were separated on thin-layer chromatography (TLC) plates, and their mutagenic effects tested by direct application of the Salmonella assay onto sections of the developed chromatoplate. The Rf of one component (0.62) corresponded to the one obtained for a tinidazole standard and showed the expected mutagenicity, while a second component with an Rf=0.39, exhibited a mutagenic potency slightly greater than the observed for tinidazole; however, as in the case of the drug itself, reduction of the nitro group was necessary for a mutagenic activity.

N-oxidation: a possible route of tinidazole metabolism in man.

Treatment of tinidazole with a mixture of hydrogen peroxide and acetic acid, or liver homogenate preparations, yields the N-3 oxide. This was identified by thin-layer chromatographic analysis on silica gel G, Rf 0.6, using ethanol-chloroform-ammonia (50:49:1) as solvent, and by chemical reduction with sulphur dioxide. UV spectrophotometry and high performance liquid chromatography (HPLC) gave an RT of 0.55 min using Pye Unicam apparatus equipped with a UV detector at 330 nm, a reversed-phase RP 18 (10 microns) column which was 12.5 cm long, a mobile phase of methanol-0.005 M KH2PO4 (pH 4) (20:80, v/v) and a flow rate of 2 ml/min. In-vitro metabolic N-oxidation was achieved by incubating the parent drug, tinidazole, with rat liver homogenates fortified with cofactors at 37 degrees C. HPLC analysis of blood and urine samples from healthy volunteer subjects who took a single oral dose of tinidazole showed the presence of an in-vivo N-oxidation metabolite of the drug. The identical physico-chemical characteristics of the synthetic and biologically produced tinidazole N-oxide strongly suggest that tinidazole, a tertiary amine drug, undergoes metabolic N-oxidation.

Effect of enzyme induction and inhibition on the fate of metronidazole and tinidazole in the rat.

The excretion routes of intact metronidazole and tinidazole were studied in rats kept in metabolism cages and cannulated for continuous bile collection. The nitroimidazoles were given intraarterially either alone or after a 5-day pretreatment with phenobarbitone (70 mg/kg/day intravenously) or after a single dose of cimetidine (50 mg/kg intraarterially). After 30 mg/kg, 27.0% of the metronidazole dose was excreted intact in 24-hr urine and 2.2% in bile. After tinidazole, the recoveries of the intact drug in urine and bile were 48.1% and 1.7%, respectively. After 90 mg/kg, the total recoveries of both drugs were 25-28% smaller than after 30 mg/kg. Phenobarbitone pretreatment did not affect metronidazole levels in plasma but decreased tinidazole levels at 4 hrs. The 24-hr recoveries of the intact nitroimidazoles in urine were significantly reduced by phenobarbitone while the 24-hr bile recoveries were not. Cimetidine treatment enhanced both metronidazole (at 1, 2 and 3 hrs) and tinidazole (only at 1 hr) concentrations in plasma, but this shift was not reflected in the 24-hr urine recoveries of the intact nitroimidazoles. Cimetidine doubled, however, the 24-hr bile recovery of the intact tinidazole. The calculations of the apparent degree of metabolism, assuming no methodological losses, showed that phenobarbitone increased the metabolism of tinidazole by about 62% and that of metronidazole only by about 16%. The effect of a single dose of cimetidine was negligible.

Pharmacokinetics and metabolism of 14C-tinidazole in humans.

Following intravenous infusion of 800 mg of 14C-tinidazole during 30 min to two human subjects, a mean of 44% of the dose was excreted in urine during the first 24 h, increasing to 63% of the dose during five days: 12% of the dose was excreted in the faeces, indicating the possible involvement of biliary excretion and other secretory processes in the disposition of tinidazole. At 6 min after the end of the infusion, the mean plasma tinidazole concentration was 12 mg/l. Tinidazole was a major component in 0-120 h urine (about 32% of urinary 14C): the major metabolite in the 0-12 h urine examined was ethyl 2-(5-hydroxy-2-methyl-4-nitro-1-imidazolyl)ethyl sulphone (about 30% urinary 14C), the product of hydroxylation and nitro-group migration. These compounds were also present in the faeces. A minor urinary metabolite was 2-hydroxymethyltinidazole (about 9% urinary 14C), which was also present in plasma. The mean pharmacokinetic parameters obtained for tinidazole were similar to those reported in the literature; total clearance 51 ml/min, renal clearance 10 ml/min, volume of distribution 501 and half-life 11.6 h.

Radiosensitization by tinidazole: pharmacokinetic study.

In previous study on cell-cultures, the authors have proved that tinidazole had radiosensitizing properties on hypoxic cells similar to those of metronidazole. The radiosensitizing activity of tinidazole becomes useful in vitro using a concentration of 1 millimol. The purpose of this study was to determine the dose of tinidazole necessary to produce a useful radiosensitizing effect in patients cured by radiotherapy. The pharmacokinetic properties of tinidazole were studied by treating patients with 1.5-3-4.5 g of the drug per day, using single doses for two consecutive days. The plasma concentration was determined by 15 series samples during a period of 48 h. Moreover endotumoural concentrations of tinidazole were studied in a group of patients using high pressure liquid chromatography techniques. The results showed that a dose of 4.5 g of tinidazole was sufficient to reach plasmatic and endotumoural concentrations similar to those which provide a radiosensitizing effect in vitro with an enhancement factor ratio of approximately 1.5. The initial dose and the accumulation factor were also determined in order to maintain the above-mentioned concentrations for a time sufficient to be able to apply multiple daily fractions of radiotherapy. The tolerance of the drug throughout the study was excellent.

Concentrations of metronidazole and tinidazole in male genital tissues.

The steady-state concentrations of metronidazole and tinidazole in male genital tissues were analyzed in patients subjected to elective gonadal surgery. The nitroimidazoles were administered orally at 500 mg every 8 h, beginning 5 days before the operation. Eight hours after the last dose, the concentrations of tinidazole were 24.1 +/- 2.5 micrograms (mean +/- standard error of the mean)/g of prostatic tissue, 29.1 +/- 2.9 micrograms/g of vas deferens, 22.1 +/- 2.1 micrograms/g of epididymis, and 18.6 +/- 2.3 micrograms/g of testis. The corresponding values of metronidazole were 14.3 +/- 1.8 micrograms/g, 15.9 +/- 1.2 micrograms/g, 14.0 +/- 1.2 micrograms/g, and 12.5 +/- 1.7 micrograms/g, respectively.

Comparative pharmacokinetics of metronidazole and tinidazole and their tissue penetration.

Since metronidazole and tinidazole are used prophylactically against infections after colorectal surgery, their pharmacokinetics and that of hydroxy-metronidazole were compared in 34 such patients. Seventeen patients received a single dose of 1.5 g (50-min infusion) of either agent 1 h before the operation. The concentrations of serum and tissue homogenates (subcutaneous fat, omentum, peritoneum, ileum, appendix, colon) were assayed by high-pressure liquid chromatography. The serum concentrations 1 h after start of infusion were 34.1 +/- 6.7 mg/l of metronidazole, 2.3 +/- 1.2 mg/l of OH-metronidazole, and 35.2 +/- 6.3 mg/l of tinidazole. OH-metronidazole and tinidazole were detectable for 72 h and metronidazole for 48 h. The ranges of serum and tissue concentrations (subcutaneous fat, omentum, peritoneum, ileum, appendix, colon) overlapped (within one single standard deviation). The tissue concentrations were high, particularly in intestinal tissues, except that the levels were low in subcutaneous tissue. The serum half-life of metronidazole was 9.0 +/- 1.6 h, of OH-metronidazole 14.8 +/- 7.4 h, and of tinidazole 16.4 +/- 3.8 h. The terminal-phase distribution volume was 35.8 +/- 10.01 for metronidazole and 40.6 +/- 9.91 for tinidazole, and the total body clearance 2.7 +/- 1.2 l/h and 1.8 +/- 0.5 l/h, respectively. The slower disposition of OH-metronidazole, which inhibits anaerobic bacteria, prolongs the duration of bioactivity in the body after metronidazole to that reached by tinidazole. OH-tinidazole was not detected in patient specimens (assay standards ensured that it could be assayed).(ABSTRACT TRUNCATED AT 250 WORDS)

Tinidazole milk excretion and pharmacokinetics in lactating women.

Five women undergoing acute Caesarean section were given an i.v. dose of 1600 mg tinidazole preoperatively as prophylaxis against anaerobic infection. Blood and breast milk samples were collected at 8 and 4 h intervals, respectively, for 120 h. Tinidazole concentrations were measured by means of high performance liquid chromatography (h.p.l.c). The concentration of tinidazole in breast milk was highly related to the concentration in serum (r = 0.969). Tinidazole concentrations in serum declined monoexponentially with an average half-life of 11.4 h (range 8.7-13.1). The milk/serum concentration ratio varied between 0.62 and 1.39. Seventy-two hours after the Caesarean section the milk concentration exceeded 0.5 microgram/ml in only one woman. It may be calculated that at this time the maximum daily dose to the infant would be 0.1 mg/kg body weight (assuming 3.5 kg body weight and 400 ml milk consumed). We conclude that until tinidazole has been proven harmless to the neonate breast feeding following i.v. administration of 1600 mg should not be initiated earlier than 72 h after the dose.

A novel metabolite of tinidazole involving nitro-group migration.

After oral doses to dogs of 14C-tinidazole, a 5-nitroimidazolyl antiprotozoal compound, a major and previously unidentified radioactive metabolite was isolated from urine and shown by FAB mass spectrometry and n.m.r. spectroscopy to be ring-hydroxylated. The exact identity of this metabolite was established by X-ray diffraction analysis as ethyl 2-(5-hydroxy-2-methyl-4-nitro-1-imidazolyl)ethyl sulphone. The apparent migration of the nitro group from the 5 position in the parent drug to the 4 position in the metabolite is a novel metabolic route.

Uptake of antimicrobial agents by human polymorphonuclear leucocytes.

The uptake of the antimicrobial agents tinidazole, josamycin and penicillin G by normal human polymorphonuclear leucocytes (PMNs) was measured in vitro, using radiolabeled drugs. Extracellular concentrations corresponding to therapeutically effective serum levels of the drugs were used. Penicillin G penetrated the leucocyte membrane poorly, the ratio of the cell-associated to the extracellular concentration (C/E) being between 0.23 and 0.54. In contrast, tinidazole and josamycin were accumulated by the cells: C/E for tinidazole varied from 1.38 to 1.56 and C/E for josamycin from 3.5 to 21.4, depending on incubation times. It is inferred that these two compounds are capable of inactivating intracellular organisms and would therefore be useful for treating or preventing chronic infections caused by pathogens which survive intracellularly. The extraordinarily high accumulation of josamycin by PMNs could not easily be reversed by repeated cell washing and might be explained by the existence of an active transport mechanism.

Placental transfer of metronidazole and tinidazole in early human pregnancy after a single infusion.

Concentrations of metronidazole and tinidazole were analysed in mother's serum, placental tissue and foetal tissue after a single intravenous infusion of 500 mg of either drug in 21 patients who underwent a first trimester legal abortion. At the time of the evacuation (60 min from the start of the infusion) the concentrations of metronidazole and tinidazole in serum were 13.6 +/- 0.6 micrograms/ml and 13.2 +/- 0.4 micrograms/ml, respectively. In foetal tissue the concentrations of metronidazole and tinidazole reached 66% and 58%, and in placental tissue 26% and 37%, of the respective serum values.

Prophylaxis with tinidazole in oral surgery. Tissue penetration and effect on the oral microflora.

10 patients with odontogenic cysts were given 500 mg tinidazole orally every 12 h for infection prophylaxis before cystectomy. The administration started 48 h before operation and lasted for 7 days. Samples for assay of tinidazole were collected from blood plasma and cystic fluid during surgery. Saliva samples for microbiological studies of the normal flora were obtained before, during and after the antibiotic administration period. Mean concentrations of tinidazole in plasma and cystic fluid were 10.7 mg/l and 10.0 mg/l, respectively. The anaerobic flora was suppressed in all patients and two patients were colonized with enterobacteria, and two with fungi. No anaerobic bacterial strains resistant to tinidazole emerged during the treatment period. It is concluded that tinidazole can be administered prophylactically 48 h before oral surgery, in order to obtain maximal tissue concentration, without risk of the emergence of resistant bacterial strains or severe ecological disturbances of the oral microflora.

Tinidazole pharmacokinetics in severe renal failure.

The single-dose pharmacokinetics of intravenously and orally administered tinidazole were studied in normal subjects and patients with severe chronic renal failure. The clearance of tinidazole was also measured in patients on regular haemodialysis. After intravenous administration the mean elimination half-life of tinidazole was 17.1 +/- 2.3 (SD) hours in the normal subjects and 16.9 +/- 4.9 hours in patients with renal failure; the mean apparent volumes of distribution were 0.80 +/- 0.09 L/kg and 0.69 +/- 0.09 L/kg, respectively. Following oral administration the mean elimination half-life was 15.6 +/- 1.6 hours in the normal subjects and 18.4 +/- 3.5 hours in patients with renal failure; there were no statistically significant differences in these pharmacokinetic parameters. There was no accumulation of the major metabolite (hydroxymethyl tinidazole) in normal subjects or in patients with renal failure. Tinidazole clearance during haemodialysis was 71 +/- 7.7 ml/min. In the presence of renal failure no modification of tinidazole dosage would appear to be necessary. Tinidazole should be administered in full dosage following haemodialysis.

The pharmacokinetics of one single preoperative dose of metronidazole or tinidazole.

Eight patients who were subjected to colorectal surgery received 1500 mg metronidazole and another 8 patients 1600 mg tinidazole. The two groups of patients were comparable in respect to age, body size, diagnoses, types of operations, premedication, and anaesthesia. Concentrations of the parent compounds and hydroxy-metronidazole were determined by high pressure liquid chromatography in serum and tissues (subcutaneous fat, rectus abdominal muscle, peritoneum, greater omentum, distal ileum, colon, appendix). The serum and tissue concentrations of metronidazole and tinidazole were within overlapping ranges. Hydroxy-metronidazole but not hydroxy-tinidazole was detected. The total area under the serum curves was 505 (SD: +/- 181) mg . h/l for metronidazole, 137 (+/- 38) mg . h/l for hydroxy-metronidazole, and 810 (+/- 286) mg . h/l for tinidazole. The serum half-life values in the same order were 8.5, 11.2, and 14.2 hours. The distribution volume (Vd,area) were 30.1 liter for metronidazole and 38.8 liter for tinidazole. The range of tissue concentrations were completely overlapping. The two regimens can, consequently, be assessed as pharmacokinetically similar.

Comparative pharmacokinetics of metronidazole and tinidazole used as single dose prophylactic agents.

The pharmacokinetic properties of metronidazole (M) and tinidazole (T) were studied in patients undergoing colorectal surgery after a single preoperative dose of 1500 mg infused during 50 minutes. High-pressure liquid chromatography was used to determine serum concentrations, which for M and T were almost identical during the first 12 hours. After 24 hours, the concentration of T were slightly higher. Both drugs were detected in serum at 72 hours. The serum half-life (t1/2) was 9.4 hours for M and 17.6 hours for T, whereas the hydroxymetabolite of M had a t1/2 of 17.6 hours. There was considerable interindividual variation in both T and M concentrations. The prophylactic use of a single preoperative dose of 1500 mg of either M or T in elective colorectal surgery is supported by favourable pharmacokinetic properties of both drugs.