Determination of sulfametrole in commercial dosage forms (Lidaprim) by TLC densitometry.
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The blanching activities of Betnovate cream, lotion, ointment and scalp application (each containing 0.1% betamethasone (as the 17-valerate] were determined using healthy human subjects over a 32 h period in both the occluded and unoccluded modes. Considering that all four formulation types contained the same label concentration of corticosteroid, it may be presumed that the formulations would show similar topical drug availability: this was, however, not found to be the case. The scalp application demonstrated the highest topical availability in both the occluded and unoccluded modes. The lotion formulation showed the greatest increase in topical availability on occlusion and the ointment formulation was the least sensitive to the effects of occlusion. These differences, due solely to the effects of the vehicle, may have important clinical implications.
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Sustained release hydrodynamically balanced capsules (HBS) of propranolol.HCl have been prepared and evaluated in vitro. Data to support the mechanism of drug release from the HBS capsule are also presented. Floating behaviour of the HBS capsule has also been seen in vivo with the help of endoscopy.
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The comparative bioavailability of two phenytoin products, Phenytoin Sodium (CAPS (Pvt) Ltd) and Epanutin (Parke-Davis (Pty) Ltd) was studied. Single dose studies carried out in eight healthy volunteers showed that CAPS Phenytoin exhibited a small but significantly higher bioavailability (P less than 0.05). The AUC (0-72 hr) for CAPS Phenytoin was 50.61 microgram/ml/hr compared to 45.09 au/ml/hr for Epanutin. The time to peak concentrations, Tmax, was significantly longer in CAPS Phenytoin when compared to Epanutin being 3.75 hr and 3.25 hr respectively (P less than 0.05) and the peak concentrations Cmax, achieved after single dose administration showed that CAPS Phenytoin exhibited higher levels than Spanutin (1.76 au/ml and 1.58 au/ml respectively) although these differences were not statistically significant. Multiple dose studies carried out in four healthy volunteers and two epileptic patients showed that changes from one product to the other did not produce any significant differences in the steady state phenytoin levels.
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The absolute and relative bioavailability of nifedipine (1) from different formulations administered as single oral doses in healthy volunteers was determined. Serum concentrations of 1 were measured by GC. The absolute bioavailability of 1 was 53% because of presystemic metabolism. The bioavailability of Adalat (Bayer) tablets, Nifedipina (Terapia) and Corinfar (VEB Arzneimittelwerk Dresden) sugar-coated tablets was 93%, 92% and 86% (respectively) as compared with Adalat capsules. The AUC were not significantly different. The Cmax and tmax values were different, indicating that the absorption of 1 showed differences in first-order rate constants of dissolution in the above mentioned order. Despite the differences among the formulations studied, each preparation may have its merits. In a multiple dose regimen of 20 mg 1 (Nifedipina, Terapia) t.i.d., minimal therapeutic drug levels were achieved and maintained during steady state, from the 1st d of treatment.
Timolol base was prepared from its maleate salt and checked for purity, pKa (9.03) and n-octanol/phosphate buffer pH 6.6 partition coefficient (1.72). The rate of swelling of sodium carboxymethylcellulose, Carbopol 934 (CP) and hydroxypropylcellulose (HPC) was examined prior to use in bioadhesive compacts with the model drug methylene blue to study their influence on device integrity and drug diffusion. A final compact containing a core of timolol base and Precirol, a bioadhesive layer of CP and HPC, and a cap of magnesium stearate gave sustained release of the drug in simulated saliva pH 6.6. After preliminary evaluation in dogs, the compact was evaluated in a panel of humans in whom it was shown that the flux of drug could be increased from 70 to 127 micrograms mm-2 h-1 by inclusion of the penetration enhancer sodium lauryl-sulphate into the core formulation.
In-vitro dissolution of theophylline from six commercially sustained-release (SR) preparations (Euphyllin retard, Euphyllin retard mite, Theovent L.A. 125 mg, Theovent L.A. 250 mg, Phyllocontin and Uniphyllin) was determined by using rotating basket and rotating bottle apparatus. The effect of pH and rotating speed on the dissolution rate of these SR products was also studied. Scanning electron microscope was used to observe the change of surface topograph and inner texture of these products before, during and after dissolution. The results indicates that the dissolution behavior was pH-dependent which corresponding to the types of SR products. The rotating bottle method was only suitable for the evaluation of release rate of spansule-type SR products and was not suitable for matrix-type SR tablets due to the sticking occurred on the bottle surface leading to faster dissolution and larger variation. The release mechanism of these six SR products can be deduced into three models. Fickian transport (Phyllocontin), non-Fickian transport (Euphyllin, Theovent L.A. 250 mg and Uniphyllin) and zero order transport (Theovent L.A. 125 mg).
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Fenticonazole vaginal ovules of 200 mg, 600 mg and 1,000 mg were administered to 42 women prior to gynecological surgery. Tissue concentrations in the vaginal mucosa were determined after 3 h and 12 h in biopsy specimens taken from the same position in the posterior fornix. Tissue concentrations were higher at 3 h in comparison to 12 h with all 3 doses. There was no statistical difference between the concentrations yielded by the 3 different ovules at 3 h, while after 12 h the concentrations were dose-dependent and significantly higher after 1,000 mg in comparison to 200 mg, but not to 600 mg.
A rapid reverse phase liquid chromatographic method was developed for the determination of levodopa and levodopa-carbidopa in tablets and capsules. The method also separates these drugs from 3-(3,4,6-trihydroxyphenyl)alanine and methoxytyrosine, impurities of levodopa, and from methyldopa and 3-O-methylcarbidopa, impurities of carbidopa. The mobile phase was 3% acetic acid and the detection wavelength was 280 nm. The method was linear over the concentration range 0.05-0.40 mg levodopa/mL, 0.01-0.06 mg carbidopa/mL, 0.9-12.8 micrograms 3-(3,4,6-trihydroxyphenyl)alanine/mL, 0.7-3.1 micrograms methyldopa/mL, 5-20 micrograms methoxytyrosine/mL, and 0.5-3.3 micrograms 3-O-methylcarbidopa/mL. Mean recoveries (%) for spiked commercial tablets were: levodopa 100.3, carbidopa 100.4, 3-(3,4,6-trihydroxyphenyl)alanine 99.1, methoxytyrosine 100.0, methyldopa 100.0, and 3-O-methylcarbidopa 99.4.