Quantitative determinations of two decongestants and an antihistamine in combination using paired ion high-pressure liquid chromatography.

A single method for the quantitative determinations of three active ingredients, phenylephrine hydrochloride, phenylpropanolamine hydrochloride, and brompheniramine maleate, and one inactive ingredient (sodium benzoate) in a commercial product for colds is reported. The method is based on paired ion high-pressure liquid chromatography using 1-heptanesulfonic acid as the counterion. It is accurate and precise. The relative standard deviations based on six readings are reported. This method is sensitive; less than 1 microgram of each ingredient can be assayed. The peak area of each ingredient is related to its concentration.

Quantitative determinations of codeine phosphate, guaifenesin, pheniramine maleate, phenylpropanolamine hydrochloride, and pyrilamine maleate in an expectorant by high-pressure liquid chromatography.

The quantitative determinations of codeine phosphate, guaifenesin, pheniramine maleate, phenylpropanolamine hydrochloride, and pyrilamine maleate in a liquid dosage form are described. All active and inactive ingredients (sodium benzoate and FD&C Yellow No. 5 dye) can be separated with high-pressure liquid chromatography except the two antihistamines, pheniramine maleate and pyrilamine maleate. Pheniramine maleate is determined colorimetrically, and pyrilamine maleate is determined either by difference or spectrophotometrically. The methods are simple short, accurate, and precise. The standard deviations are reported.

Stability-indicating methods for quantitative determination of spironolactone using high-pressure liquid chromatography and blue tetrazolium reaction.

Stability-indicating methods for the quantitative determination of spironolactone were developed. The methods are based on high-pressure liquid chromatography and a reaction with blue tetrazolium. Both methods are accurate, precise, and sensitive and gave excellent results with commercial tablets, including those containing hydrochlorothiazide in addition to spironolactone, The blue tetrazolium method cannot be used in the presence of high concentrations of either polyethylene glycols or water. Spironolactone decomposition in water or polyethylene glycol appears to follow pseudo-first-order kinetics. The decomposition constant at 65 degrees was 0.0253/day in water versus 0.115/day in polyethylene glycol ointment base USP.

Applications of paired ion high-pressure liquid chromatography to catecholamines and phenylephrine.

Paired ion high-pressure liquid chromatography was useful for separating intact catecholamines (epinephrine, isoproterenol, levodopa, and methyldopa) and phenylephrine from some of their decomposition products. Furthermore, methyldopa was separated from either hydrochlorothiazide of levodopa. Under identical conditions without 1-heptanesulfonic acid (a counterion for paired ion chromatography) in the mobile phase, these separations were not possible. Paired ion chromatography also was tried successfully for the quantitative determinations of isoproterenol, levodopa, methyldopa, and phenylephrine in some dosage forms. The results were compared with the results obtained using some literature methods.

Stability of furosemide in aqueous systems.

A stability-indicating assay for furosemide based on high-pressure liquid chromatography was developed. The method is sensitive, accurate, and precise. The standard deviation based on six injections of the standard solution was +/- 1.37%. This method was used to study furosemide stability in various aqueous solutions and dosage forms. Stability tests were conducted at room temperature as well as at higher temperatures (45, 65, and 85 degrees) at various pH values and with different vehicles. Some decomposition products were identified.

Quantitative determination of four antihistamines in combination by high-pressure liquid chromatography.

A procedure used to assay four antihistamines--brompheniramine maleate, chlorpheniramine maleate, pheniramine maleate and pyrilamine maleate in combination--is discussed. The method requires a high-pressure liquid chromatograph and an intermediate polarity column. The method is accurate and appears to be stability-indicating. The four antihistamines can be separated and assayed accurately. There is no interference from the two commonly used decongestants, phenylephrine hydrochloride and phenylpropanolamine hydrochloride, from the expectorant potassium guaiacolsulfonate, from the preservative propyl paraben or from two other antihistamines, diphenhydramine hydrochloride and bromdiphenhydramine hydrochloride. Guaifenesin, methylparaben and sodium benzoate interfere only with pheniramine maleate. Methapyrilene hydrochloride interferes only with pyrilamine maleate.

Stability of pediatric liquid dosage forms of ethacrynic acid, indomethacin, methyldopate hydrochloride, prednisone and spironolactone.

The stability of liquid dosage forms of ethacrynic acid (1 mg/ml), indomethacin (2 mg/ml), methyldopate hydrochloride (25 mg/ml), prednisone (0.5 mg/ml) and spironolactone (2 mg/ml), which often are compounded extemporaneously, was studied. One or two liquid dosage forms of each of the five drugs was prepared with the pure drug or the powder from a commercial dosage form using aqueous sorbitol or simple syrup alone or with a 10% (v/v) solution of alcohol in water. The dosage forms were stored at 24 C in amber-colored bottles for 21-224 days and assayed by various methods. All solutions studied were stable for at least 84 days. A solution was considered stable if it retained 90% of its drug concentration. Except for the prednisone solution, all solutions were stable for at least 164 days; however, the solution of methyldopate hydrochloride prepared from the pure drug became discolored after 98 days. The liquid dosage forms studied have limited stability but can be used by the pharmacist when extemporaneous oral solutions of these drugs are needed.