Comparative bioavailability study of cefuroxime axetil (equivalent to 500 mg cefuroxime/tablet) tablets (Zednad® versus Zinnat®) in healthy male volunteers.

This study was performed to investigate the bioequivalence of cefuroxime axetil tablets between a generic test product (A) Zednad® Tablet (500 mg cefuroxime/ tablet, Diamond Pharma, Syria), and the Reference Product (B) Zinnat® Tablet (500 mg cefuroxime/tablet, GlaxoSmithKline, Saudi Arabia). The bioavailability study was carried out for 24 healthy male volunteers. The subjects received 1 Zednad® Tablet (500 mg/ tablet) and 1 Zinnat® Tablet (500 mg/tablet) in a randomized, two-way crossover design fashion on 2 treatment days, after an overnight fast of at least 10 h, with a washout period of 7 days. 24 volunteers plus 2 alternatives completed the crossover. The bioanalysis of clinical plasma samples was accomplished by HPLC method, which was developed and validated in accordance with international guidelines. Pharmacokinetic parameters, determined by standard non-compartmental methods, and ANOVA statistics were calculated using SAS Statistical Software. The significance of a sequence effect was tested using the subjects nested in sequence as the error term. The 90% confidence intervals for the ratio between the test and reference product pharmacokinetic parameters of AUC0→t, AUC0→∞, and Cmax were calculated and found to be within the confidence limits of 80.00 - 125.00% for AUC0→t, AUC0→∞ and Cmax. The study demonstrated that the test product (A) was found bioequivalent to the reference product (B) following an oral dose of 500 mg tablet. Therefore, the two formulations were considered to be bioequivalent.

Bioequivalence evaluation of 320 mg gemifloxacin tablets in healthy volunteers.

This study was done to compare the bioavailability of a new tablet formulation of gemifloxacin (gemifloxacin 320 mg/tablet) with that of the reference product (factive 320 mg/tablet). The bioequivalence of a single dose (320 mg) was assessed for gemifloxacin included in the test and reference products by comparing the pharmacokinetic parameters derived from the plasma concentration-time profiles following administration to 24 healthy male volunteers in a balanced, 2-period, 2-sequence, 2-way crossover design. Plasma concentrations of gemifloxacin were analyzed by a validated and sensitive HPLC assay developed in-house. The mean plasma concentration-time profiles are almost superimposable. 18 ANOVAs were performed to compare gemifloxacin plasma levels of the two formulations at each sampling time and there were no statistical differences between the two formulations. The parameters used to measure bioavailability were AUC0-t, AUC0-infinity and Cmax and they were calculated by a model-independent method. The parametric 90% confidence intervals of the mean values for the test/reference ratio were in each case well within the bioequivalence acceptable boundaries of 80-125% for AUCo-t, AUC0-infinity and Cmax. Data obtained in this study prove, by appropriate statistical methods, the essential similarity of plasma levels of gemifloxacin from the test product with those from the reference product suggesting equal clinical efficacy of these two products.

Comparative bioavailability study of cefixime (equivalent to 100 mg/5 ml) suspension (Winex vs Suprax) in healthy male volunteers.

This investigation was carried out to evaluate the bioavailability of a new suspension formulation of cefixime (100 mg/5 ml), Winex, relative to the reference product, Suprax (100 mg/5 ml) suspension. The bio-availability study was carried out in 24 healthy male volunteers who received a single oral dose (200 mg) of the test (A) and the reference (B) products on 2 treatment days after an overnight fast of at least 10 hours. The treatment periods were separated by a one-week washout period. A randomized, balanced two-way crossover design was used. After dosing, serial blood samples were collected over a period of 16 hours. Plasma concentrations of cefixime were analyzed using a sensitive high-performance liquid chromatographic assay. The pharmacokinetic parameters for cefixime were determined using standard non-compartmental method. The parameters AUC(0-t), AUC(0-infinity), Cmax, Kel, t1/2 and Cmax/AUC(0-infinity) were analyzed statistically using raw and log-transformed data. The time to maximum concentration (tmax) was analyzed using raw data. The parametric 90% confidence intervals of the mean values of the pnfinity harmacokinetic parameters: AUC(0-t), AUC(0-infinity) Cmax, and Cmax/AUC(0-infinity) were within the range 80 - 125% which is acceptable for bioequivalence (using log-transformed data). The calculated 90% confidence intervals based on the ANOVA analysis for the mean test/reference ratios of AUC(0-t), AUC(0-infinity), Cmax, and Cmax/AUC(0-infinity) were 88.93 - 107.10%, 89.09 - 107.11%, 89.63 - 108.58% and 96.85 - 105.29%, respectively. The test formulation was found bioequivalent to the reference formulation with regard to AUC(0-t), AUC(0-infinity), and Cmax using the Schuirmann's two one-sided t-tests. Therefore, the two formulations were considered to be bioequivalent.

Comparative bioavailability study of doxycycline hyclate (equivalent to 100 mg doxycycline) capsules (doxycin vs vibramycin) for bioequivalence evaluation in healthy adult volunteers.

This investigation was carried out to evaluate the bioavailability of a new capsule formulation of doxycycline (100 mg), doxycin, relative to the reference product, vibramycin (100 mg) capsules. The bioavailability was carried out in 24 healthy male volunteers who received a single dose (100 mg) of the test (A) and the reference (B) products after an overnight fast of at least 10 hours on 2 treatment days. The treatment periods were separated by a 2-week washout period. A randomized, balanced 2-way cross-over design was used. After dosing, serial blood samples were collected for a period of 48 hours. Plasma concentrations of doxycycline were analyzed by a sensitive and validated high-performance liquid chromatography assay. The pharmacokinetic parameters for doxycycline were determined using standard noncompartmental methods. The parameters AUC(0-t), AUC(0-infinity), Cmax, K(el), t(1/2) and Cmax/AUC(0-infinity) were analyzed statistically using log-transformed data. The time to maximum concentration (tmax) was analyzed using raw data. The parametric 90% confidence intervals of the mean values of the pharmacokinetic parameters: AUC(0-t), AUC(0-infinity), Cmax and Cmax/AUC(0-infinity) were within the range 80-125% which is acceptable for bioequivalence (using log-transformed data). The calculated 90% confidence intervals based on the ANOVA analysis of the mean test/reference ratios of AUC(0-t), AUC(0-infinity), Cmax and Cmax/AUC(0-infinity) were 95.98-109.56%, 92.21 to 107.66%, 93.90-112.56%, and 96.0 to 106.91% respectively. The test formulation was found bioequivalent to the reference formulation with regard to AUC(0-t), AUC(0-infinity), Cmax and Cmax/AUC(0-infinity) by the Schuirmann's two 1-sided t-tests. Therefore, the 2 formulations were considered to be bioequivalent.

Effect of lamotrigine on the pharmacokinetics of carbamazepine and its active metabolite in dogs.

The effect of lamotrigine (LTG) on the pharmacokinetics of carbamazepine (CBZ) and its active metabolite; carbamazepine-epoxine (CBZ-E), was investigated in dogs. Five male dogs received CBZ (2 x 200 mg tab, p.o.) daily for a period of 1 week. After the end of this period, blood samples were collected serially for up to 24 hrs. After a wash-out period of I week, LTG (100 mg tab, p.o.) was coadministered with the CBZ dose (2 x 200 mg tab, p.o.) for 7 days. Blood samples were again serially collected and plasma levels of CBZ and CBZ-E were analysed by high performance liquid chromatography (HPLC). Concurrent administration of LTG with CBZ did not have any significant effect on the pharmacokinetic parameters of CBZ. There was also no significant difference between the plasma concentration ratio (CBZ-E to CBZ) vs time profiles in the two schedules of drug administration signifying the absence of pharmacokinetic interaction between LTG and CBZ or its active metabolite in this animal model.

Liquid chromatographic assay of nifedipine in human plasma and its application to pharmacokinetic studies.

A highly sensitive, selective and reproducible reversed-phase high-performance liquid chromatographic method has been developed for the determination of nifedipine in human plasma with minimum sample preparation. The method is sensitive to 3 ng/ml in plasma, with acceptable within- and between-day reproducibilities and linearity (r2 > 0.99) over a concentration range from 10-200 ng/ml. Acidified plasma samples were extracted using diethyether containing diazepam as internal standard and chromatographic separation was accomplished on C18 column using a mobile phase consisting of acetonitrile, methanol and water (35:17:48, v/v). The within-day precision ranged from 2.22 to 4.64% and accuracy ranged from 102.4-106.4%. The day-to-day precision ranged from 2.34-7.07% and accuracy from 95.1-100.1%. The relative recoveries of nifedipine from plasma ranged from 91.0-107.3% whereas extraction recoveries were 88.6-93.3%. Following eight 6-week freeze-thaw cycles, nifedipine in plasma samples proved to be stable with accuracy ranging from 0.64 to 3.0% and precision ranging from 3.6 to 4.15%. Nifedipine was also found to be photostable for at least 120 min in plasma, 30 min in blood and for 60 min in aqueous solutions after exposure to light. The method is sensitive and reliable for pharmacokinetic studies and therapeutic drug monitoring of nifedipine in humans after the oral administration of immediate-release capsules and sustained-release tablets to five healthy subjects.

Bioequivalence evaluation of two brands of cefuroxime 500 mg tablets (Cefuzime and Zinnat) in healthy human volunteers.

A bioequivalence study of two oral formulations of 500 mg cefuroxime axetil was carried out in 24 healthy volunteers following a single dose, standard two-treatment cross-over design at the College of Pharmacy, King Saud University, Riyadh, Saudi Arabia, working jointly with King Khalid University Hospital. The two formulations used were Cefuzime (Julphar, United Arab Emirates) as the test and Zinnat (Glaxo Wellcome, England) as the reference product. Both test and reference tablets were administered to each subject after an overnight fasting on two treatment days separated by a 1-week washout period. After dosing, serial blood samples were collected for a period of 8 h. Plasma harvested from blood was analysed for cefuroxime by a sensitive, reproducible and accurate high pressure liquid chromatography (HPLC) method. Various pharmacokinetic parameters including AUC(0-t), AUC(0-infinity), C(max), T(max), T(1/2) and K(el) were determined from plasma concentrations of both formulations and found to be in good agreement with reported values. AUC(0-t), AUC(0-infinity) and C(max) were tested for bioequivalence after log-transformation of data. No significant difference was found based on an analysis of variance (ANOVA); 90% confidence interval for test/reference ratio of these parameters were found within bioequivalence acceptance range of 80-125%. Based on these statistical inferences, it was concluded that Cefuzime is bioequivalent to Zinnat.

Bioequivalence evaluation of lomefloxacin 400 mg tablets (Lomax versus Maxaquin in healthy human volunteers.

This study represents the results of a randomized, single dose, two-treatment, two-period crossover study in 18 healthy male volunteers to assess the bioequivalence of two tablets of 400 mg lomefloxacin. The two formulations were: Lomax(R) (Julphar, United Arab Emirates) as the test formulation and Maxaquin(R) (Searle, S.A., UK) as the reference formulation. The study was conducted at the College of Pharmacy, King Saud University, Riyadh, Saudi Arabia, jointly with King Khalid University Hospital, Riyadh, Saudi Arabia. After overnight fasting the two products were administered as a single dose on two treatment days separated by a 1 week washout period. Serial blood samples were collected thereafter, for a period of 48 h. Plasma harvested from blood was analysed for lomefloxacin by a sensitive, reproducible and accurate HPLC method. Various pharmacokinetic parameters including AUC(0-t), AUC(0-infinity), C(max,) T(max), T(1/2), K(elm) and C(max)/AUC(0-infinity) were determined from plasma concentrations for both formulations and found to be in good agreement with reported values. Statistical modules applied to AUC(0-t), AUC(0-infinity) and C(max) revealed no significant difference in the two tested products. Based on these statistical inferences it was concluded that Lomax(R) is bioequivalent to Maxaquin(R).

High-performance liquid chromatographic determination of furosemide in plasma and urine and its use in bioavailability studies.

A sensitive, selective and efficient reversed-phase high-performance liquid chromatographic (HPLC) method is reported for the determination of furosemide in human plasma and urine. The method has a sensitivity limit of 5 ng/ml in plasma, with acceptable within- and between-day reproducibilities and good linearity (r2>0.99) over a concentration range from 0.05 to 2.00 microg/ml. The one-step extract of furosemide and the internal standard (warfarin) from acidified plasma or urine was eluted through a muBondapak C18 column with a mobile phase composed of 0.01 M potassium dihydrogenphosphate and acetonitrile (62:38, v/v) adjusted to pH 3.0. Within-day coefficients of variation (C.V.s) ranged from 1.08 to 8.63% for plasma and from 2.52 to 3.10% for urine, whereas between-day C.V.s ranged from 4.25 to 10.77% for plasma and from 5.15 to 6.81% for urine at three different concentrations. The minimum quantifiable concentration of furosemide was determined to be 5 ng/ml. The HPLC method described has the capability of rapid and reproducible measurement of low levels of furosemide in small amounts of plasma and urine. This method was utilized in bioavailability/pharmacokinetic studies for the routine monitoring of furosemide levels in adults, children and neonate patients.

Comparative bioavailability of two tablet formulations of ranitidine hydrochloride in healthy volunteers.

This investigation was carried out to evaluate the bioavailability of a new tablet formulation of ranitidine HCl (300 mg), Ranid, relative to the reference product, Zantac, (300 mg) tablets. The bioavailability was carried out on 24 healthy male volunteers who received a single dose (300 mg) of the test (T) and the reference (R) products in the fasting state, in a randomized balanced 2-way crossover design. After dosing, serial blood samples were collected for a period of 16 hours. Plasma harvested from blood was analyzed for ranitidine by a sensitive and validated high-performance liquid chromatographic assay. The maximum plasma concentration (Cmax), area under the plasma concentration time curve up to the last measurable concentration (AUC0-t), and to infinity (AUC0-infinity) and the absorption rate (Cmax/AUC0-infinity) were analyzed statistically under the assumption of a multiplicative model. The time to maximum concentration (Tmax) was analyzed assuming an additive model. The parametric confidence intervals (90%) of the mean values of the pharmacokinetic characteristics (AUC0-t, AUC0-infinity), Cmax and Cmax/AUC0-infinity) for T/R ratio were in each case well within the bioequivalence acceptable range of 80-125%. The test formulation was found bioequivalent to the reference formulation by the Schuirmann's two one-sided t-tests and by Wilcoxon Mann Whitney two one-sided tests procedure. Therefore, the 2 formulations were considered to be bioequivalent.

Comparative bioavailability of two tablet formulations of acyclovir in healthy volunteers.

This investigation was carried out to evaluate the bioavailability of a new tablet formulation of acyclovir (400 mg), Clovir, relative to reference product, Zovirax (400 mg) tablets. The 2 brands were found to be similar in weight variation, disintegration time, dissolution, and assay as stipulated by the USPXXIII, as well as by the manufacturer. The bioavailability was carried out on 24 healthy male volunteers who received a single dose (400 mg) of the test (T) and the reference (R) products in the fasting state, in a randomized balanced 2-way crossover design. After dosing, serial blood samples were collected for a period of 16 hours. Plasma harvested from blood was analyzed for acyclovir by a sensitive and validated high-performance liquid chromatographic assay. The maximum plasma concentration (Cmax), area under the plasma concentration-time curve up to the last measurable concentration (AUC0-t), and to infinity (AUC0-infinity), and the absorption rate (Cmax/AUC0-infinity) were analyzed statistically under the assumption of a multiplicative model. The time to maximum concentration (Tmax) was analyzed assuming an additive model. The parametric confidence intervals (90%) of the mean values of the pharmacokinetic characteristics (AUC0-t, AUC0-infinity, Cmax, Cmax/AUC0-infinity) for T/R ratio were in each case, well within the bioequivalence acceptable range of 80-125%. The test formulation was found bioequivalent to the reference formulation by the Schuirmann's two 1-sided t tests and by Wilcoxon Mann Whitney two 1-sided tests procedure. Therefore, the 2 formulations were considered to be bioequivalent.

Determination of pefloxacin and its main active metabolite in human serum by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of a fluoroquinolone, pefloxacin, and its main active metabolite norfloxacin (N-desmethyl metabolite) in serum. Sample preparation involves protein precipitation with acetonitrile. The drugs and the internal standard (acebutolol) were eluted from a 4-microns Novapak C-18 cartridge at ambient temperature with an isocratic mobile phase consisting of 14% acetonitrile in buffer solution, at a flow rate of 2.5 ml/min. The effluent was monitored on a fluorescence detector using excitation and emission wave-lengths of 330 and 440 nm, respectively. Each analysis required no longer than 8 min. Quantification was achieved by measurement of the peak-area ratio of the drugs to the internal standard, and the limit of quantification for both pefloxacin and norfloxacin in serum was 50 ng/ml. The intraday coefficient of variation (CV) ranged from 1.3 to 4.4% and from 2.2 to 7.5% for pefloxacin and norfloxacin, respectively, at the concentration ranges evaluated. The interday CV ranged from 1.1 to 5.9% and from 2.3 to 5.6% for pefloxacin and norfloxacin, respectively, at three concentrations. Relative recovery was 105.5 and 99.5% for pefloxacin and norfloxacin, respectively. Stability tests show that pefloxacin and norfloxacin are stable in serum for at least 3 weeks when stored at -20 degrees C. This method has been used successfully in pharmacokinetic studies in humans.

Comparative bioavailability of two tablet formulations of ibuprofen.

This investigation was carried out to evaluate the bioavailability of a new tablet formulation of ibuprofen (600 mg), Profinal, relative to reference product, Brufen (600 mg) tablets. The 2 brands were found to be similar in assay, weight variation and dissolution as stipulated by the USP XXII, as well as the disintegration time, as specified by the BP 1988. The bioavailability was carried out on 18 healthy male volunteers who received a single dose (600 mg) of the test (T) and the reference (R) products in the fasting state, in a randomized balanced 2-way crossover design. After dosing, serial blood samples were collected for a period of 12 hours. Plasma harvested from blood was analyzed for ibuprofen by a sensitive and validated high-performance liquid chromatographic assay. The maximum plasma concentration (Cmax), area under the plasma concentration-curve up to the last measurable concentration (AUC0-t), and to infinity (AUC0-infinity) were analyzed statistically under the assumption of a multiplicative model. The time to maximum concentration (Tmax) was analyzed assuming an additive model. The parametric confidence intervals (90%) of the mean values of the pharmacokinetic characteristics (AUC0-t, AUC0-infinity and Cmax) for T:R ratio were in each case, well within the bioequivalence acceptable range of 80-125%. The test formulation was found bioequivalent to the reference formulation by the Schuirmann's 2 1-sided t-tests and by Wilcoxon-Mann-Whitney 2 1-sided tests procedure. Therefore, the 2 formulations were considered to be bioequivalent.

Effect of famotidine on ciprofloxacin pharmacokinetics after single intravenous and oral doses in rats.

The effect of intravenous (3.5 mg/kg) and oral (5 mg/kg) famotidine on ciprofloxacin pharmacokinetics after single (i.v.) intravenous (5 mg/kg) and oral (20 mg/kg) doses were examined in the rat. Famotidine co-administration significantly increased the terminal elimination half-life of ciprofloxacin (54% and 29% following i.v. and oral administration, respectively) and tended to reduce the total body clearance by 27% and 34% following i.v. and oral routes, respectively. The area under the plasma concentration-time curve and the mean residence time in the body after i.v. and oral doses were significantly increased following famotidine co-administration. No changes in the steady-state apparent volume of distribution was observed after i.v. administration. The maximum plasma concentration and the time to peak concentration after oral dosing were also unaffected. These results suggest a possible reduction in the total clearance of ciprofloxacin, owing to inhibition of its renal tubular excretion by famotidine. Further studies are warranted to determine whether this interaction occurs in humans.

Microcomputer program for the assessment of one-way, two-way and factorial analysis of variance in pharmaceutical data.

A personal computer program in BASIC for the two-factor factorial analysis of variance has been developed. The factorial design is based on and combined with previous one-way and two-way ANOVA programs. The performance of the program is tested on data obtained from 3 months' consumption of three proprietary antibiotic products in four Saudi hospitals.

Effect of pirenzepine on the N-demethylation of D(-)ephedrine and ethylmorphine by rabbit liver microsomes.

The possible interaction of pirenzepine with the mixed-function oxidases obtained from phenobarbital-pretreated rabbit microsomes was examined in vitro. Under experimental conditions that did not lead to its own N-demethylation, the drug inhibited the microsomal oxidase systems responsible for the N-demethylation of D(-)ephedrine and ethylmorphine. Kinetic studies showed that pirenzepine inhibited the metabolism of both drugs in a competitive manner. The results indicated that the observed pirenzepine stability to the hepatic N-demethylating system is not a result of low affinity of the drug to the system.

A simple high-performance liquid chromatographic assay for ciprofloxacin in human serum.

A simple and selective high-performance liquid chromatographic (HPLC) method for the determination of ciprofloxacin in serum has been developed and evaluated. Serum protein was precipitated with acetonitrile. The drug and the internal standard (quinine) were evaluated from a 10 microns U-Bondapack C-18 cartridge at ambient temperature with a mobile phase consisting of acetonitrile: 0.1 M sodium dihydrogen phosphate (20:80%, v/v) adjusted to pH 3.9 with phosphoric acid, and at a flow rate of 2.5 ml/min. The effluent was monitored on a fluorescence detector using an excitation and emission wavelength of 280 and 455 nm, respectively. Each analysis required no longer than 6 min. Quantification was achieved by the measurement of the peak-height ratio and the limit of quantification for ciprofloxacin in serum is 25 ng/ml. The intraday coefficient of variation (CV) ranged from 0.4 to 5.8%, and interday CV from 4.6 to 8.8% at three different concentrations. Relative recovery ranged from 98 to 100.2% at three different concentrations. Preliminary stability tests show that ciprofloxacin is stable for at least 3 weeks in serum after freezing.

Comparative study of Saudi-marketed products and US drug labeling.

Drug package inserts from ten nonsteroidal antiinflammatory drugs marketed in Saudi Arabia were compared with their corresponding US labels to determine possible differences in their information content. These variations were assessed with special regard to the number of words used and the type of the information provided. The study showed that inserts of Saudi-marketed products generally conveyed limited and incomplete information. Possible adverse reactions, drug--drug interactions, and date of revision often were not included, although this information was present on the corresponding US labels. Comparisons of the package inserts of the same product from various pharmaceutical companies show wide variations in the amount of information provided. Determining the minimal level of information that must be included by the manufacturer in the package insert and the establishment of firm international guidelines by the World Health Organization could effectively reduce such variations.

Phenytoin-bupropion interaction: effect on plasma phenytoin concentration in the rat.

The effect of coadministration of bupropion (50 mg kg-1, p.o.) on the disposition profile of phenytoin has been studied in the rat. Plasma phenytoin concentration was measured serially for 10 h by HPLC. Bupropion had little or no effect on the pharmacokinetic parameters of an acutely administered dose of phenytoin. Following multiple doses of phenytoin however (i.e. steady state) the coadministration of bupropion resulted in significant increases in the elimination half-life (t 1/2), the area under the plasma concentration-time curve (AUC) and the time to maximum plasma concentration (tmax). Allowing for the limitations of single dose studies, these results point to a possible pharmacokinetic interaction between bupropion and phenytoin--the clinical significance of which needs to be assessed.

First-derivative UV spectrophotometric assay of domperidone.

Domperidone in pure form and in a number of pharmaceutical formulations (Motilium) has been determined in 0.5-N sulphuric acid by employing first-derivative at 294 nm and zero-order at 284 nm spectrophotometric modes. The results obtained by utilizing the first derivative procedure were 99.98 +/- 0.47, 101.70 +/- 0.53, 101.70 +/- 0.53 and 101.15 +/- 1.23 for the tablets, oral suspension, drops and suppositories respectively. In a similar way the results obtained for the zero order technique were 105.38 +/- 1.01, 101.70 +/- 2.57, 108.56 +/- 1.16 and 102.23 +/- 3.37 in the order. The standard addition method was adopted to evaluate the accuracy of the first derivative spectrophotometric mode.