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ABSTRACT: A method for the in vitro determination of low- and high-value sun protection factors (SPF) of sunscreens using artificial substrates and a novel pseudo double beam (PDB) mode of operation of a standard double beam UV spectrophotometer is described. The method allows transmittance to be calculated from detector responses of reference and sample beams measured at different gain levels and facilitates the accurate quantification of low levels of electromagnetic radiation transmitted through highly absorbing samples. The spectrophotometer was modified to hold quartz diffusing plates on which a substrate [Transpore adhesive tape or human stratum corneum obtained from a skin surface biopsy (SSB)] and the sunscreens to be tested were applied. The PDB mode of operation increased the effective linear range of the detector response of the spectrophotometer by a factor of approximately 20000-fold, enabling the in vitro SPF determination technique to be applied to both high and low SPF value sunscreens. Eight commercial sunscreens with known SPF values ranging from 4 to 77, previously determined by in vivo methods, were tested in vitro using both test substrates and correlations between the in vivo and in vitro values were determined. SPF values determined using the in vitro method correlated well with the known in vivo results (Transpore tape, R(2) = 0.611; SSB, R(2) = 0.7928). The in vitro SPF obtained for one of the tested products differed substantially from the cited in vivo SPF value. Independent in vitro and in vivo re-evaluation of the SPF of this product matched the value predicted by the present method much more closely than the originally cited in vivo value. All determined SPFs were ordered correctly in comparison to in vivo ranking and the technique appeared to correctly identify a sunscreen that had a labelled SPF value that was significantly higher than its true SPF.
International journal of cosmetic science 09/2008; 30(4):259-70.
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ABSTRACT: The stability of miconazole when mixed with peritoneal dialysis (PD) fluid and stored in plastic bags or glass ampuls was determined. Admixtures of miconazole and PD fluid were prepared in 2-L polyvinyl chloride (PVC) bags and in 1-mL glass ampuls to give a nominal initial concentration of 20 mg/mL. Duplicate samples of each solution were assayed in duplicate by high-performance liquid chromatography immediately after preparation and at various intervals up to nine days. All admixtures were stored in ambient light at 20 +/- 2 degrees C. A substantial loss of miconazole (greater than 10% of the initial concentration) occurred within four hours for admixtures stored in PVC bags, whereas similar solutions retained more than 90% of their initial miconazole concentration for at least three days when stored in glass ampuls under the same conditions. This suggests that the observed loss of miconazole from the PVC bags was largely due to an interaction with the container, rather than to chemical degradation in solution. About 28% of the miconazole lost from the solution during storage in PVC bags was recovered from the plastic by methanolic extraction. The rapid loss of miconazole when the drug was mixed with PD fluid and stored in PVC bags indicates that such admixtures should be prepared immediately before administration.
American journal of hospital pharmacy 03/1991; 48(2):286-90.
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ABSTRACT: This study examines the stability of both components of the antibacterial combination, cotrimoxazole (trimethoprim and sulphamethoxazole) in peritoneal dialysis fluid stored in polyvinyl chloride bags and glass ampoules at room temperature for up to nine days. Greater than 10% loss of trimethoprim occurred within three days for admixtures stored in plastic bags, whereas the original concentration remained virtually unchanged after nine days for similar solutions stored in glass ampoules. This indicated that the loss of trimethoprim observed in solutions stored in plastic bags was associated primarily with the nature of the container, presumably due to some form of uptake by or loss through the plastic. Greater than 10% loss of sulphamethoxazole occurred within two days for all admixtures examined, stored in either glass or plastic containers. This degree of loss was achieved within 12 h for one admixture stored in plastic. There was also the time-dependent appearance of an additional peak in HPLC analyses of these solutions, indicating that loss of sulphamethoxazole was due to chemical decomposition of the drug in the peritoneal dialysis fluid. The shelf-life of such admixtures would be limited by the stability of the sulphamethoxazole component, with the available data suggesting a shelf-life of 12 h for solutions stored at room temperature.
Peritoneal dialysis international: journal of the International Society for Peritoneal Dialysis 02/1990; 10(2):157-60. · 2.10 Impact Factor
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ABSTRACT: 1. Single doses of 1,2,4-trimethylbenzene (124TMB) or 14C-124TMB were administered orally to rats for metabolism and distribution studies. 2. 14C-124TMB was rapidly and widely distributed throughout the body with the highest levels in adipose tissue. No other preferential uptake of 14C-124TMB by any of the organs or tissues examined was evident. 3. Tissue levels declined rapidly within 24 h after dosage, with more than 99% of the administered radioactivity recovered in the urine during this period. 4. A complex mixture of isomeric trimethylphenols, dimethylbenzyl alcohols, dimethylbenzoic acids and dimethylhippuric acids excreted in the urine accounted for more than 81% of the administered dose. The major metabolites were 3,4-dimethylhippuric acid (30.2% dose), 2,4-dimethylbenzyl alcohol (12.7% dose, primarily as sulphate and glucuronide conjugates) and 2,5-dimethylbenzyl alcohol (11.7% dose, primarily as sulphate and glucuronide conjugates).
Xenobiotica 03/1989; 19(2):161-70. · 1.79 Impact Factor
