Drugs online research references
J Natl Cancer Inst. 1993 Oct 20;85(20):1685-90.
Measurement of cremophor EL following taxol: plasma levels sufficient to reverse drug exclusion mediated by the multidrug-resistant phenotype.
Webster L, Linsenmeyer M, Millward M, Morton C, Bishop J, Woodcock D.
Peter MacCallum Cancer Institute, Melbourne, Victoria, Australia.
BACKGROUND: Paclitaxel (Taxol) is the first of a new class of cytotoxic agents with activity against tumors resistant to other drugs. For clinical use, paclitaxel is currently formulated in a vehicle of 50% ethanol and 50% polyethoxylated surfactant Cremophor EL (Cremophor). We have previously shown that Cremophor will block the P-glycoprotein drug efflux pump responsible for the multidrug-resistant phenotype. Overexpression of P-glycoprotein is one mechanism of in vitro resistance to a number of currently used cytotoxic agents including paclitaxel. PURPOSE: Our aim was to develop a bioassay to measure plasma levels of Cremophor and to determine whether or not plasma levels of Cremophor achieved during paclitaxel therapy are sufficient to inhibit the activity of the P-glycoprotein. METHODS: All patients studied had histologically proven, advanced ovarian carcinoma with measurable or evaluable disease and had received at least one prior platinum-containing regimen. The bioassay used flow cytometry to measure the increase in equilibrium intracellular daunorubicin levels in multidrug-resistant human T-cell leukemia cells (CEM/VLB100) in the presence of a series of concentrations of Cremophor. Levels of Cremophor were measured in plasma from 21 patients after a 3-hour infusion of 135 or 175 mg/m2 paclitaxel. Both dose levels were given following premedication with oral dexamethasone, intravenous promethazine hydrochloride, and intravenous cimetidine. The Cremophor bioassay involved incubation of CEM/VLB100 cells (5 x 10(5)) for 1 hour with 2 micrograms/mL daunorubicin in 0.5 mL HL-1 medium plus 0.5 mL plasma prior to flow cytometric analysis. Pretreatment plasma was used to derive a standard curve for the effect of Cremophor on equilibrium daunorubicin levels. All measurements were done in triplicate. RESULTS: In vitro experiments indicated that, for maximal inhibition of P-glycoprotein activity, concentrations of Cremophor of 0.1% (vol/vol) were required. At the end of a 3-hour infusion of paclitaxel, plasma levels of Cremophor in 19 of 21 patients were 0.1% or higher and 0.09% in the remaining two. Concentrations of 5-20 microM paclitaxel dissolved in ethanol without Cremophor did not inhibit P-glycoprotein in this assay. CONCLUSION: The concentrations of Cremophor measured in plasma drawn from patients after a 3-hour infusion of paclitaxel at 135 or 175 mg/m2 were found to be sufficient to inhibit P-glycoprotein activity in vitro. IMPLICATIONS: The efficacy of paclitaxel against some tumors may be aided by its administration in a vehicle solution containing Cremophor in quantities that reach concentrations in the plasma sufficient to reverse multidrug resistance of neoplastic cells.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8105099&dopt=Abstract
Pharm World Sci. 1994 Feb 18;16(1):18-21.
The preservation of some oral liquid preparations. The replacement of chloroform by other preservatives.
van Doorne H, Leijen JB.
Department of Pharmaceutical Technology and Biopharmacy, University of Groningen, The Netherlands.
Chloroform should be considered as an obsolete preservative for pharmaceutical preparations, because of its toxicological implications and its physical instability. The effectiveness of possible alternatives for chloroform in three oral liquid pharmaceutical preparations was investigated, using a microbiological challenge test. Magnesium trisilicate mixture (British Pharmacopoeia) can be adequately preserved with methylparaben (2 g/l). Only insignificant amounts of methylparaben were absorbed by the solids present in the magnesium trisilicate mixture. Ferrous sulfate mixture (British Pharmacopoeia) can be preserved with a mixture of methylparaben (1.8 g/l) and propylparaben (0.2 g/l). Sorbic acid (1 g/l) is a suitable preservative for promethazine hydrochloride syrup.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8156044&dopt=Abstract
Biull Eksp Biol Med. 1978 Oct;86(10):471-4.
[Inhibition of non-cytotoxic histamine liberation from isolated rat mast cells by antihistaminic preparations]
[Article in Russian]
Gushchin IS, Kaminka ME, Deriugin IL.
Phenothiazines (chlorpromazine and promethazine) and antihistaminic quinuclidine derivatives [phencarol, quinuclidyl-3-di-(o-tolyl) carbinol, hydrochloride quinuclidyl-3-di-(o-methoxyphenyl) carbinol--HQMC] at concentrations preceding the histamine-releasing ones inhibited the compound 48/80-induced histamine release from the isolated rat mast cells. HQMC inhibited histamine release induced by selective liberators (compound 48/80, MCD-peptide, specific antigen), but potentiated histamine release induced by nonselective liberators (chlorpromazine, tryton X-100). The inhibition by HQMC of histamine release induced by compound 48/80 increased during 1 min and was reversible. The inhibitory effect of all the compounds tested was partially counteracted by glucose.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=81693&dopt=Abstract
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