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PubMed1995

Issues in evaluation of bioanalytical method selectivity and drug stability.

Evaluation of selectivity is one of the most controversial aspects of method validation and application of methods to studies. The focus of selectivity testing should address the question: Above what level will interference significantly impact on study conclusions? Four key issues will be addressed: the statistical relevance of any selectivity test performed; a criterion for significant interference; experimental methods to establish selectivity; and criteria for acceptance. To ensure that compound integrity is maintained throughout the work-up process, statistically meaningful methods of stability evaluation which are associated with specific acceptance criteria are required. Suitable methods for evaluating stability of analyte and/or solutions of analyte, in process stability, processed sample stability, long term stability and freeze-thaw stability, as well as meaningful acceptance criteria, are presented.

Animals↗
PubMed2002

A common mechanism of action for three mood-stabilizing drugs.

Lithium, carbamazepine and valproic acid are effective mood-stabilizing treatments for bipolar affective disorder. The molecular mechanisms underlying the actions of these drugs and the illness itself are unknown. Berridge and colleagues suggested that inositol depletion may be the way that lithium works in bipolar affective disorder, but others have suggested that glycogen synthase kinase (GSK3) may be the relevant target. The action of valproic acid has been linked to both inositol depletion and to inhibition of histone deacetylase (HDAC). We show here that all three drugs inhibit the collapse of sensory neuron growth cones and increase growth cone area. These effects do not depend on GSK3 or HDAC inhibition. Inositol, however, reverses the effects of the drugs on growth cones, thus implicating inositol depletion in their action. Moreover, the development of Dictyostelium is sensitive to lithium and to valproic acid, but resistance to both is conferred by deletion of the gene that codes for prolyl oligopeptidase, which also regulates inositol metabolism. Inhibitors of prolyl oligopeptidase reverse the effects of all three drugs on sensory neuron growth cone area and collapse. These results suggest a molecular basis for both bipolar affective disorder and its treatment.

Animals↗
PubMed1994

Tau confers drug stability but not cold stability to microtubules in living cells.

We previously defined two classes of microtubule polymer in the axons of cultured sympathetic neurons that differ in their sensitivity to nocodazole by roughly 35-fold (Baas and Black (1990) J. Cell Biol. 111, 495-509). Here we demonstrate that virtually all of the microtubule polymer in these axons, including the drug-labile polymer, is stable to cold. What factors account for the unique stability properties of axonal microtubules? In the present study, we have focused on the role of tau, a microtubule-associated protein that is highly enriched in the axon, in determining the stability of microtubules to nocodazole and/or cold in living cells. We used a baculovirus vector to express very high levels of tau in insect ovarian Sf9 cells. The cells respond by extending processes that contain dense bundles of microtubules (Knops et al. (1991) J. Cell Biol. 114, 725-734). Cells induced to express tau were treated with either cold or 2 micrograms/ml nocodazole for times ranging from 5 minutes to 6 hours. The results with each treatment were very different from one another. Virtually all of the polymer was depolymerized within the first 30 minutes in cold, while little or no microtubule depolymerization was detected even after 6 hours in nocodazole. Based on these results, we conclude that tau is almost certainly a factor in conferring drug stability to axonal microtubules, but that factors other than or in addition to tau are required to confer cold stability.

Animals↗
PubMed1981

Determination of drug stability in aspirin tablet formulations by high-pressure liquid chromatography.

Salicylic acid and aspirin were resolved from the other salicylates in thermally degraded multicomponent tablets and determined quantitatively. The analytical method involved wetting the powdered tablet with acetic acid and diluting with chloroform to extract the drug components. Automated high-pressure liquid chromatographic analyses of filtered extracts were performed on a silica column with a mobile phase of acetic acid in heptane. The method was capable of resolving the major thermally induced transformation products in tablet formulations. It was sensitive to approximately 0.1 mg of salicylic acid/tablet. Good agreement with the compendial method for free salicylic acid was obtained.

Aspirin↗
PubMedDate not supplied

Interpretive criteria, quality control guidelines, and drug stability studies for susceptibility testing of cefotaxime, cefoxitin, ceftazidime, and cefuroxime against Neisseria gonorrhoeae.

Cefotaxime, cefoxitin, ceftazidime, and cefuroxime were tested in a multicenter study to establish susceptibility testing criteria and quality control guidelines for Neisseria gonorrhoeae. Interpretive criteria were established by using triplicate testing of at least 100 gonococcal strains having various susceptibility patterns to currently utilized drug regimens. Only a susceptible category was proposed for cefotaxime and ceftazidime (greater than or equal to 31 mm and less than or equal to 0.5 micrograms/ml) because of rare resistant isolates. The other interpretive crtieria were cefoxitin susceptible, greater than or equal to 28 mm (less than or equal to 2 micrograms/ml); intermediate, 24-27 mm (4 micrograms/ml), and resistant, less than or equal to 23 mm (greater than or equal to 8 micrograms/ml); cefuroxime-susceptible, greater than or equal to 31 mm (less than or equal to 1 micrograms/ml); moderately susceptible, 26-30 mm (2 micrograms/ml); and resistant, less than or equal to 25 mm (greater than or equal to 4 micrograms/ml). Quality control criteria were established by using multiple agar lots, three disk lots, and a number of replicates consistent with National Committee for Clinical Laboratory Standards M23-T guidelines.

Cefotaxime↗
PubMedDate not supplied

[Higher microsomal monooxygenase activity in chloroquine-resistant strains of malarial plasmodium as a possible cause of drug stability].

Ability to hydroxylate benz(alpha)pyrene--a substrate of arylhydrocarbone hydroxylase (AHH) was distinctly increased in lysates of erythrocytes containing malarial plasmodium. Hydroxylation of benz(alpha)pyrene was inhibited by methyrapone--an inhibitor of microsomal monooxygenases. Activity of AHH was increased from 2- to 3-fold in chloroquine-resistant plasmodium strains as compared with the drug-sensitive strains. Resistance of Plasmodium berghei to chloroquine appears to involve an activation of the monooxygenases system in the parasite.

Animals↗
PubMed1992

An electrically modulated drug delivery device. III. Factors affecting drug stability during electrophoresis.

A number of factors affecting the stability of propranolol HCl during electrophoretic control were investigated. It was found that significant degradation of propranolol HCl and hydrolysis of water occurred when a current of 15 mA was used with platinized electrodes. This degradation was thought to be due to decomposition of propranolol HCl at the electrodes. Degradation could be significantly reduced by using uncoated platinum electrodes and currents in the range of 0 to 2.5 mA, while still allowing control of drug delivery rates. Electrode reaction processes were found at high ionic strengths and high drug concentrations but were not thought to be associated with drug decomposition.

Chromatography, High Pressure Liquid↗