Pharmacological studies on Myrica rubra Sieb et zucc. Effects on the cardiovascular system and platelets.

UNLABELLED: The effects of 50% Drink of Myrica rubra (MRD) on the cardiovascular system of the rat and on the platelets aggregation of rats and guinea pigs were studied. METHOD: Different groups of male Wistar rats were treated either with 50% Myrica rubra drink as drinking vehicle (4 weeks) or water. The animals were then prepared for the measurement of arterial blood pressure and heart rate, ECG, sensitivity of the baroreceptors, platelets' aggregation, blood clotting time and cardiac parasympathetic ganglia. The mechanism of action of any induced effect was elucidated using different receptor blockers. RESULTS: Treatment induced a significant decrease in the arterial blood pressure and heart rate on Wistar rats, but no significant changes in the ECG were observed. Pretreatment of rats with MRD 10 or 20 ml/kg (i. p.) significantly suppressed vagal electrical stimulation to the heart and nicotine-induced bradycardia, via decreasing phenylephrine-induced rise in the arterial blood pressure and the reflexly-induced bradycardia. It significantly suppressed the Baroreceptor Sensitivity Index (BSI). The treatment also significantly suppressed ADP-induced platelets aggregation in rats and arachidonic acid-induced aggregation in guinea pigs.All these actions seemed to be mediated by the MRD constituents such as proanthocyanidins, polyphenols and flavonoids. The decreases in the heart rate and BSI were probably caused by an inherent ability to block the parasympathetic ganglia. CONCLUSION: The results of this study regarding the effects of MRD actions on the cardiovascular system and platelets qualify the drink to be classified as a functional food.

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.

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.