Drugs online research references
J Control Release. 1999 Jun 2;59(3):327-42.
Identification of critical formulation and processing variables for metoprolol tartrate extended-release (ER) matrix tablets.
Rekhi GS, Nellore RV, Hussain AS, Tillman LG, Malinowski HJ, Augsburger LL.
Department of Pharmaceutical Sciences, University of Maryland, School of Pharmacy, Baltimore, MD 21201-1180, USA.
The objective of this study, was to examine the influence of critical formulation and processing variables as described in the AAPS/FDA Workshop II report on scale-up of oral extended-release dosage forms, using a hydrophilic polymer hydroxypropyl methylcellulose (Methocel K100LV). A face-centered central composite design (26 runs+3 center points) was selected and the variables studied were: filler ratio (lactose:dicalcium phosphate (50:50)), polymer level (15/32.5/50%), magnesium stearate level (1/1.5/2%), lubricant blend time (2/6/10 min) and compression force (400/600/800 kg). Granulations (1.5 kg, 3000 units) were manufactured using a fluid-bed process, lubricated and tablets (100 mg metoprolol tartrate) were compressed on an instrumented Manesty D3B rotary tablet press. Dissolution tests were performed using USP apparatus 2, at 50 rpm in 900 ml phosphate buffer (pH 6.8). Responses studied included percent drug released at Q1 (1 h), Q4, Q6, Q12. Analysis of variance indicated that change in polymer level was the most significant factor affecting drug release. Increase in dicalcium phosphate level and compression force were found to affect the percent released at the later dissolution time points. Some interaction effects between the variables studied were also found to be statistically significant. The drug release mechanism was predominantly found to be Fickian diffusion controlled (n=0.46-0.59). Response surface plots and regression models were developed which adequately described the experimental space. Three formulations having slow-, medium- and fast-releasing dissolution profiles were identified for a future bioavailability/bioequivalency study. The results of this study provided the framework for further work involving both in vivo studies and scale-up.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10332064&dopt=Abstract
Eur J Drug Metab Pharmacokinet. 1994 Oct-Dec;19(4):375-80.
Stable isotope methodology for studying the performance of metoprolol Oros tablets in comparison to conventional and slow release formulations.
Richard J, Cardot JM, Godbillon J.
Centre de Bioanalyse et Pharmacocinetique, Laboratories Ciba-Geigy, Rueil-Malmaison, France.
Metoprolol Oros tablets were designed to deliver their drug content as a constant rate over a period of time longer than that currently recorded with slow-release dosage forms. The bioavailability of 7/95, 14/190 and 21/285 Oros tablets was compared to that of either 100 mg conventional or 200 mg slow-release Lopresor tablets in 3 two-period change over experiments. In each experiment, 6 healthy volunteers received intravenous deuterated metoprolol concomitantly with one of the Oros systems or with one of the other two formulations. The Oros tablets gave rise to lower and steady plasma levels of metoprolol over 24 h than the other formulations. Their mean absorption time was around 3 times longer than that of the slow-release tablets. The amount of the drug absorbed unchanged was linearly related to the dose. The influence of the gastrointestinal transit time on the performance of Oros tablet was limited. These studies demonstrated the value of the stable isotope methodology in bioavailability assessment for drugs presenting a high inter-subject variability in their plasma clearance such as metoprolol.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7737240&dopt=Abstract
Clin Auton Res. 1993 Dec;3(6):363-8.
Effect of antihypertensive formulation on health service expenditures.
Sclar DA, Skaer TL, Robison LM, Chin A, Okamoto MP, Nakahiro RK, Gill MA.
College of Pharmacy, Washington State University, Pullman 99164-6510.
A major barrier to the management of hypertension is the extent to which patients comply with the treatment regimen. Herein we report the findings of a retrospective analysis designed to discern the relationship between antihypertensive formulation, regimen compliance and the utilization of health care services. Data for this analysis were derived from the state of South Carolina's Medicaid computer archive. The study population consisted of 1,000 randomly selected beneficiaries initially prescribed one of the following antihypertensive regimens as monotherapy: atenolol (daily); captopril (twice daily); oral clonidine (twice daily); transdermal clonidine (once a week); diltiazem (twice daily); enalapril (twice daily); metoprolol (twice daily); prazosin (twice daily); terazosin (daily); and verapamil-SR (daily). Multivariate regression analysis was used to determine the incremental influence of selected demographic characteristics, utilization of medical services prior to diagnosis for hypertension, initial antihypertensive medication, medication possession ratio for antihypertensive therapy, and the number of maintenance medications for disease state processes other than hypertension on post-period health care expenditure. Results indicate that patients initially prescribed antihypertensive medication requiring daily or weekly administration experience infrequent changes in their therapeutic regimen, far less use of concomitant therapy for blood pressure control, an increased utilization of antihypertensive medication, and a decrease in the use and cost of physician, hospital and laboratory services.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8193522&dopt=Abstract
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