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Biomedical subjects

M F Powell

Publications and source records attributed to M F Powell.

49 records · Page 3Linked to original sources
PubMed1987

Temperature and pH dependence of fluocinolone acetonide degradation in a topical cream formulation.

We investigated the degradation of fluocinolone acetonide (FA) incorporated into an oil-in-water cream base. The study examined the influence of temperature (23 to 80 degrees C) and cream pH (pH 2.3 to 6) on FA degradation rates. FA degradation followed pseudo-first-order kinetics and adhered to the Arrhenius expression over the entire temperature range investigated. At all temperatures, the pH strongly influenced the observed degradation rate constant (kobs) values, with rate minima observed near pH 4. The FA log(degradation rate)-pH profiles were consistent with a reaction mechanism requiring drug hydrolysis catalyzed by hydroxide and hydrogen ions. Taking into account both the temperature and the pH dependence of FA degradation permits calculating kobs values from the following equation: kobs = exp[22.5 - (17,200/RT)] + exp[38.7 - (22,200/RT)] x [H+] + exp[49.5 - (21,100/RT)] x [OH-] where the three bracketed terms represent Arrhenius expressions for neutral, acid-catalyzed, and base-catalyzed hydrolysis reactions. FA degradation in the cream base parallels the degradation of a related steroid (triamcinolone acetonide) in an aqueous alcohol solution. The equivalence between FA and triamcinolone acetonide kinetics in the different reaction media suggests that in the cream base, FA degradation is limited to an aqueous phase largely unperturbed by the presence of nonaqueous constituents that comprise the cream formulation.

Acids↗
PubMed1987

Stability of lidocaine in aqueous solution: effect of temperature, pH, buffer, and metal ions on amide hydrolysis.

The degradation of lidocaine in aqueous solution obeys the expression kobs = (kH+[H+] + ko) [H+]/([H+] + Ka) + k'oKa/([H+] + Ka) where kH+ is the rate constant for hydronium ion catalysis, and ko and k'o are the rate constants for the spontaneous (or water-catalyzed) reactions of protonated and free-base lidocaine. At 80 degrees C, the rate constants for these processes are 1.31 x 10(-7) M-1 sec-1, 1.37 x 10(-9) sec-1, and 7.02 x 10(-9) sec-1; the corresponding activation energies are 30.5, 33.8, and 26.3 kcal mol-1, respectively. It was found that the room temperature pH of maximum stability is approximately 3-6 and that lidocaine is more reactive in the presence of metal ions such as Fe2+ and Cu2+. The dissociation constant, Ka, for lidocaine at 25-80 degrees C was also measured at 0.1 M ionic strength and a plot of pKa versus 1/T gave a slope of (1.88 +/- 0.05) x 10(3) K-1 and intercept 1.56 +/- 0.16.

Amides↗
PubMed1986

Enhanced stability of codeine sulfate: effect of pH, buffer, and temperature on the degradation of codeine in aqueous solution.

In the absence of strong buffer catalysts, the degradation of codeine sulfate (7,8-didehydro-4,5 alpha-epoxy-3-methoxy-17-methylmorphinan-6 alpha-ol sulfate) in aqueous solution is described by the expression kobs = kH+ [H+] + k0 + kHO-[HO-], where kH+ = (3.9 +/- 1.3) X 10(-8) M-1 X S-1, k0 = (2.7 +/- 0.5) X 10(-8) S-1, and kHO- = (5.1 +/- 1.0) X 10(-6) M-1 X S-1 at 80 degrees C. The activation energies associated with these rate constants are 27.7, 21.0, and 28.3 kcal X mol-1, respectively. In the absence of buffer catalysis, codeine sulfate is predicted to have a room temperature shelf life of approximately 44 years between pH 1 and 10, significantly longer than the 1.1 year shelf life of codeine phosphate reported earlier.

Buffers↗
PubMed1985

Twenty-four hour emergency pharmaceutical services.

Operation of an emergency department satellite pharmacy in which the pharmacist provided clinical, educational, and drug distribution services during patient visits is described. In a Detroit trauma and ambulatory-care center, drugs were dispensed to outpatients 24 hours a day from a satellite pharmacy located in the 75-bed emergency department. Emergency department pharmaceutical services were expanded to include distributive, clinical, and educational activities by the pharmacist on a 24-hour basis. The pharmacist contributed to improved inventory control and billing for drug products. When reductions in the work force were necessary, the institution chose to retain 24-hour pharmacist coverage during emergency department patient visits and to eliminate 24-hour dispensing to outpatients. In this urban trauma center, the emergency department pharmacist's clinical, distributive, and educational services contributed substantially to delivery of patient care.

Education, Pharmacy↗
PubMed1983

Evaluation of a cardiopulmonary-resuscitation training manual for pharmacists.

The development and evaluation of a training manual for pharmacists participating in cardiopulmonary resuscitation (CPR) efforts at an institution encompassing ambulatory-care, acute-care, and emergency-trauma facilities are described. The manual was developed to familiarize pharmacists who had little or no experience in CPR procedures with the equipment and medications used and the pharmacist's role on the CPR team. To evaluate the effectiveness of the manual, a 29-question multiple-choice test was administered to 35 staff pharmacists who were randomly assigned to study and control groups. Training manuals were issued to members of the study group, who were asked to document time spent studying them. Three weeks after the pretest, the same test was administered to all subjects. There was no control on the number of CPR events attended during the three-week period. The study group spent less than two hours (mean +/- S.D. = 97.5 +/- 34.22 min) using the manual. For the study group, posttest scores were significantly higher than pretest scores. The difference in pretest scores for the study and control groups was not significant, but for the posttest the study group scores were significantly higher. Because use of the manual appeared to improve knowledge of drug therapy and procedures used in CPR, the pharmacy department incorporated it into its orientation procedure.

Education, Pharmacy, Continuing↗
PubMed1982

Concerning 1e- transfer in reduction by dihydronicotinamide: reaction of oxidized flavin and flavin radical with N-benzyl-1,5-dihydronicotinamide.

The rates of reaction of 5-ethyl-3-methyllumiflavinium perchlorate and 5-ethyl-3-methyllumiflavinyl radical with a NADH analogue, N-benzyl-1,4-dihydronicotinamide, were measured anaerobically in tert-butanol and 5% acetonitrile/95% tert-butanol solutions at 30 degrees C. The biphasic kinetics observed for the reaction of flavin radical with dihydronicotinamide were interpreted in terms of both a 1e- and a 2e- mechanism; the former was found to be inadequate based on experimental requirements of the mechanism. The dihydronicotinamide reacts preferentially with oxidized flavin rather than flavin radical, even when the concentration of oxidized flavin is at a concentration 5 orders of magnitude less than that of radical. These studies show that the "hydride" reduction of oxidized flavin by BNAH is more facile than is the 1e- reduction of flavin radical by BNAH.

Electron Transport↗
PubMed1979

Diabetic patient compliance as a function of patient counseling.

The impact of a specially designed patient education program upon the diabetes-related knowledge and compliance of insulin dependent diabetic patients was investigated. The program consisted of an audiovisual presentation, illustrated handout material, and pharmacist-patient counseling. Based on statistical considerations, 65 eligible patients were assigned systematically to a control group (Group I) and a study group (Group II) and were evaluated for compliance following a standardized protocol. Immediately following the interview, Group II patients were instructed utilizing the patient education program. Scores for initial and final evaluations of knowledge and compliance were compared using appropriate statistical procedures. The program was successful in producing improvements in both knowledge and compliance but a need for individualization of patient education efforts was indicated. Significant improvements in compliance were not observed among patients older than the mean age for study patients and those with diabetes complicated by cardiovascular and hypertensive disease.

Attitude to Health↗