Simultaneous determination of chlorzoxazone and acetaminophen in combined dosage forms by an absorbance ratio technique and difference spectrophotometry.

Two spectrophotometric methods have been developed for the simultaneous determination of chlorzoxazone and acetaminophen in their combined dosage forms. No preliminary separation step is required in either method. The first, an absorbance ratio technique using the isoabsorptive point as one of the wavelengths, together with "Q curve" analysis gives accurate and reproducible results for both drugs. The second, a difference spectrophotometric method is based on measurement of absorbance of an alkaline solution relative to that of an acidic solution of identical concentration of the sample at two different wavelengths. The method is suitable for routine analysis of such combinations of the drugs.

Simultaneous spectrophotometric determination of mefenamic acid and paracetamol in pharmaceutical preparations.

A spectrophotometric procedure for the simultaneous determination of mefenamic acid and paracetamol in a mixture is described. Using 0.01 M methanolic hydrochloric acid as solvent, the absorbance of the mixture is measured at 248, 279 and 351 nm. The concentration of each component can be calculated by solving two equations using two wavelengths, either 248 and 279 nm or 248 and 351 nm.

Spectrophotometric assays of diloxanide furoate and tinidazole in combined dosage forms.

Two spectrophotometric methods have been developed for the simultaneous determination of diloxanide furoate and tinidazole in combined dosage formulations without prior separation. The first method is based on the measurement of the absorbance of a methanolic solution of the sample at 259 and 311 nm and application of a simplified Vierordt equation for the determination of diloxanide furoate, whereas tinidazole is determined by direct spectrophotometry. The second method is a difference spectrophotometric procedure based on measurement of the absorbance of the sample solution in water relative to that of an acidic or alkaline solution of identical concentration at the appropriate wavelength of maximum difference absorption. The results are calculated by reference to standard absorptivity values.

Antagonism of anthracene-9-carboxylic acid as screening test for muscle relaxants.

Veratrinic response produced by anthracene-9-carboxylic acid in mice has been used as a model for studying effect of variety of drugs which induce muscle relaxation. None of the drugs listed as general depressants, central muscle relaxants, neuromuscular blocking agents and anti-convulsants were effective even at doses causing 100% loss of righting reflex. Local anaesthetics/direct acting muscle relaxants were effective. This simple model employed in conjunction with Straub's tail test can differentiate various categories of muscle relaxants and their mechanism of action.

Investigations of nicandrenone--a withanolide-like aromatic plant steroid from Nicandra physaloides.

On the basis of IR, UV, ORD, NMR and high resoluted mass spectral data as well as chemical transformations, evidence for structure 1 of the D-homo-aromatic plant steroid nicandrenone from Nicandra physaloides (Solanaceae) was given. The sterochemistry of both epoxy lactol functions in this compound was established using intramolecular hydrogen bonding investigations. Biogenetical aspects are discussed.