Estimation of pharmacokinetic parameters based on the patient-adjusted population data.
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Population pharmacokinetic data, adjusted for patient characteristics, are recommended for the design of initial dosage regimens of some therapeutically monitored drugs in patients for whom patient-specific data are not available. However, despite widespread use by clinicians such as pharmacists, a clear understanding of the principles of population pharmacokinetics, including data collection and analysis and its limitations, is often lacking. This article describes the 2 main methods of obtaining population kinetic data, namely the two-stage method and nonlinear mixed effect model, and their applications to the pharmacokinetic-based design of dosage regimens. Additionally, some numerical examples are provided to assist the reader in understanding the material. The author uses these tools in a pharmacokinetics course taught to PharmD students. (+info)
Stability-indicating electrochemical methods for the determination of meclophenoxate hydrochloride and pyritinol dihydrochloride using ion-selective membrane electrodes.
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The construction and electrochemical response characteristics of polyvinyl chloride (PVC) membrane sensors for the determination of meclophenoxate hydrochloride (I) and pyritinol dihydrochloride (II) in presence of their degradation products are described. The sensors are based on the use of the ion-association complexes of (I) and (II) cation with sodium tetraphenyl borate and ammonium reineckate counteranions as ion-exchange sites in the PVC matrix. In addition beta-cyclodextrin (beta-CD) membranes were used in the determination of I and II. These ion pairs and beta-CD were then incorporated as electroactive species with ortho nitrophenyl octyl ether (oNPOE) as a plasticizer. Three PVC sensors were fabricated for each drug, i.e. meclophenoxate tetraphenyl borate (meclo-TPB), meclophenoxate reineckate (meclo-RNC) and meclophenoxate beta-cyclodextrin (meclo-beta-CD), and the same was done for pyritinol (pyrit-TPB), (pyrit-RNC) and (pyrit-beta-CD). They showed near Nernestian responses for meclophenoxate over the concentration range 10(-5)-10(-2) with slopes of 52.73, 51.64 and 54.05 per concentration decade with average recoveries of 99.92+/-1.077, 99.96+/-0.502 and 100.03+/-0.763 for meclo-TPB, meclo-RNC and meclo-beta-CD respectively. Pyritinol also showed near Nernestian responses over the concentration range of 3.162 x 10(-6) - 3.162 x 10(-4) for pyrit-TPB and pyrit-RNC, and 10(-6) - 3.162 x 10(-4) for pyrit-beta-CD with slopes of 30.60, 31.10 and 32.89 per concentration decade and average recoveries of 99.99+/-0.827, 100.00+/-0.775 and 99.99+/-0.680 for pyrit-TPB, pyrit-RNC and pyrit-beta-CD respectively. The sensors were used successfully for the determination of I and II in laboratory prepared mixtures with their degradation products, in pharmaceutical dosage forms and in plasma. (+info)
Quality control of active ingredients in artemisinin-derivative antimalarials within Kenya and DR Congo.
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OBJECTIVES: Artemisinin-derivative drugs are widely used to treat Plasmodium falciparum malaria and very few studies have investigated the quality of these medicines in Africa. We analysed the active ingredient contents of artemisinin-derivative drugs marketed in Kenya and DR Congo. METHODS: We analysed tablets, capsules, dry suspensions and injections (IM) containing either artemether (AM), arteether (AE), artesunate (ARS) or dihydroartemisinin (DHA). The content of active ingredients and preservatives was determined quantitatively using validated HPLC-UV methods. All analyses were done according to European pharmacopoeia requirements. RESULTS: Labelled active ingredients were identified in all samples, however with varying dosages. Nine of the 24 drug samples analysed did not comply with the pharmacopoeial requirements of 95-105%: seven samples were underdosed and two were slightly overdosed. DHA was the active ingredient in 57% of the underdosed samples. AE injections had the lowest drug content (77%). Two-thirds of the dry powder suspensions were either substandard or fake. Tablets were up to 23% out of range. Unidentified peaks were observed on the chromatograms of AE IM injections and a DHA dry powder. CONCLUSIONS: Counterfeit or substandard artemisinin-derivative drugs are being sold in parts of Africa, presenting a potential route for resistance development in the future. Appropriate measures need to be taken to maintain proper and safe use of these medicines. (+info)
Stability considerations in liquid dosage forms extemporaneously prepared from commercially available products.
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The pharmacist, both in community and hospital pharmacy practice, is often challenged with the preparation of a liquid dosage form not available commercially for paediatric patients, those adults unable to swallow tablets or capsules and patients who must receive medications via nasogastric or gastrostomy tubes. Recognising the lack of information available to healthcare professionals, a general discussion of the various parameters that may be modified in preparing these dosage forms and a tabulated summary of the dosage forms presented in the literature is described, which, although not exhaustive, will provide information on the formulation and stability of the most commonly prepared extemporaneous liquid dosage forms. An extensive survey of the literature and investigation of 83 liquid dosage forms revealed that stability considerations were of concern for only 7.2% of these liquid dosage forms, extemporaneously prepared from the following commercially available products: captopril, hydralazine hydrochloride, isoniazid, levothyroxine sodium, phenoxybenzamine hydrochloride and tetracycline hydrochloride. Inclusion of the antioxidant, sodium ascorbate in the liquid dosage form for captopril resulted in improved stability at 4 degrees C. Hydralazine hydrochloride, isoniazid and phenoxybenzamine hydrochloride were adversely affected due to interactions with excipients in the formulation, while the effect of the preservative in lowering the pH in a levothyroxine sodium mixture resulted in decreased stability. Interestingly, the instability in these formulations is primarily due to interactions between the drug substance and the excipients rather than degradation of the active pharmaceutical ingredient by standard routes such as oxidation, hydrolysis, photolysis or thermolysis. This low percentage however illustrates the low risk associated with these dosage forms investigated. It may be concluded that when considering the safety and efficacy of liquid dosage forms prepared extemporaneously, it is thus important to consider not only the stability of the drug substance but the entire formulation. (+info)
Immune-mediated changes in actinic keratosis following topical treatment with imiquimod 5% cream.
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BACKGROUND: The objective of this study was to identify the molecular processes responsible for the anti-lesional activity of imiquimod in subjects with actinic keratosis using global gene expression profiling. METHODS: A double-blind, placebo-controlled, randomized study was conducted to evaluate gene expression changes in actinic keratosis treated with imiquimod 5% cream. Male subjects (N = 17) with > or = 5 actinic keratosis on the scalp applied placebo cream or imiquimod 3 times a week on nonconsecutive days for 4 weeks. To elucidate the molecular processes involved in actinic keratosis lesion regression by imiquimod, gene expression analysis using oligonucleotide arrays and real time reverse transcriptase polymerase chain reaction were performed on shave biopsies of lesions taken before and after treatment. RESULTS: Imiquimod modulated the expression of a large number of genes important in both the innate and adaptive immune response, including increased expression of interferon-inducible genes with known antiviral, anti-proliferative and immune modulatory activity, as well as various Toll-like receptors. In addition, imiquimod increased the expression of genes associated with activation of macrophages, dendritic cells, cytotoxic T cells, and natural killer cells, as well as activation of apoptotic pathways. CONCLUSION: Data suggest that topical application of imiquimod stimulates cells in the skin to secrete cytokines and chemokines that lead to inflammatory cell influx into the lesions and subsequent apoptotic and immune cell-mediated destruction of lesions. (+info)
Quantitation of nicorandil in pharmaceutical formulations by spectrophotometry using N-(1-naphthyl) ethylenediamine dihydrochloride as coupling agent.
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A validated and sensitive spectrophotometric method is developed for the quantitation of nicorandil in pharmaceutical formulations. The method is based on the reduction of nitroxy ethyl group of nicorandil to carbonyl derivative and nitrite ion by Zn/NH4Cl. The nitrite ion undergoes diazotization with sulphanilamide in presence of HCl followed by coupling with N-(1-naphthyl) ethylenediamine dihydrochloride (NED) to form a colored product with lambda(max) at 525 nm. Under the optimized experimental condition, Beer's law is obeyed in the concentration range of 0.4-12.0 microg/ml with molar absorptivity of 1.92 x 10(4) l mol(-1) cm(-1). The statistical analysis of calibration data yields the linear regression equation: A = 6.304 x 10(-4)+9.13 x 10(-2) C with correlation coefficient of 0.9999. The limits of detection and quantification are 0.05 and 0.15 microg/ml, respectively. The results obtained by the proposed method are acceptable with average recoveries of 100.0-100.1%. The results of the proposed method are compared with those of the reference method by point and interval hypothesis tests, which showed excellent agreement and there is no significant difference in accuracy and precision of methods compared. (+info)
Low dose 'Sprinkles'-- an innovative approach to treat iron deficiency anemia in infants and young children.
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Iron supplementation programs using pediatric tablets or drops have not been successful in the control of anemia amongst infants and children in India. Sprinkles is an innovative multi-micronutrient home fortification strategy to control iron deficiency and anemia. OBJECTIVE: We aimed to determine the hematologic response to different doses and forms of iron in Sprinkles and iron drops. SETTING: Twenty two villages of Vadu Rural Health Program, KEM Hospital, Pune. DESIGN: Double blind clustered randomized community-based trial. SUBJECTS: Children (n=432) aged 6 to 18 mo age with Hb between 70 to 100 g/L were enrolled. METHODS: Selected villages were randomized into 5 groups: Sprinkles 12.5, 20 or 30 mg ferrous fumarate, Sprinkles 20 mg micronized ferric pyrophosphate or drops 20 mg ferrous glycine sulphate (DROPS) for 8 weeks. Household socio-demographic information was collected at baseline. Side effects and compliance were monitored through weekly visits. Hemoglobin was estimated at baseline, 3 and 8 weeks. Ferritin was assessed at baseline and 8 weeks. RESULTS: Baseline characteristics were similar across all groups. Hemoglobin increased significantly (P<0.0001) in all groups at 8 weeks with no difference between groups. Ferritin increased (P<0.0001) significantly in all groups with no difference across the groups. Compliance (overall range: 42 to 62 %) was lowest for DROPS. Side effects were significantly higher among DROPS compared to Sprinkles (p>0.05). CONCLUSIONS: Sprinkles 12.5 mg FF dose is as efficacious as higher doses of iron in Sprinkles or DROPS in increasing hemoglobin. Sprinkles FF 12.5 mg is recommended as it has fewer reported side effects and better compliance compared to DROPS. (+info)
Drug-dispensing errors in the hospital pharmacy.
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OBJECTIVE: To determine the dispensing error rate and to identify factors associated with them, and to propose prevention actions. METHODS: A cross-sectional study focusing on the occurrence of dispensing errors in a general hospital in Belo Horizonte that uses a mixed system (a combination of multidose and unit dose systems) of collective and individualized dosing. RESULTS: A total of 422 prescription order forms were analyzed, registering 81.8% with at least 1 dispensing error. Opportunities for errors were higher in the pretyped prescription order forms (odds ratio = 4.5; P <.001), in those with 9 or more drugs (odds ratio = 4.0; P <.001), and with those for injectable drugs (odds ratio = 5.0; P <.001). One of the teams of professionals had a higher chance of errors (odds ratio = 2.0; P =.02). A multivariate analysis ratified these results. CONCLUSIONS: The dispensing system at the pharmacy can produce many latent failures and does not have an adequate control; it has several conditions that predispose it to the occurrence of errors, contributing to the high rate reported. (+info)