Aqueous stability of human epidermal growth factor 1-48.

Human epidermal growth factor 1-48 (hEGF 1-48, Des(49-53)hEGF) is a single chain polypeptide (48 amino acids; 3 disulfide bonds; 5445 Da) possessing a broad spectrum of biologic activity including the stimulation of cell proliferation and tissue growth. In this study, three primary aqueous degradation products of hEGF 1-48 were isolated using isocratic, reverse phase/ion-pair HPLC. The degradation products were characterized using amino acid sequencing, electrospray ionization mass spectrometry, isoelectric focusing, and degradation kinetics. Results indicate that hEGF 1-48 degrades via oxidation (Met21), deamidation (Asn1), and succinimide formation (Asp11). The relative contribution of each degradation pathway to the overall stability of hEGF 1-48 changes as a function of solution pH and storage condition. Succinimide formation at Asp11 is favored at pH < 6 in which aspartic acid is present mostly in its protonated form. Deamidation of Asn1 is favored at pH > 6. The relative contribution of Met21 oxidation is increased with decreasing temperature, storage as a frozen solution (-20 degrees C), and exposure to fluorescent light.

Simultaneous determination of pseudoephedrine hydrochloride, chlorpheniramine maleate, and dextromethorphan hydrobromide by second-derivative photodiode array spectroscopy.

The simultaneous determination of the active ingredients in multicomponent pharmaceutical products normally requires the use of a separation technique, such as HPLC or GC, followed by quantitation. Presented here is a rapid, validated, analytical method that does not require prior separation for the simultaneous determination of three drugs, pseudoephedrine hydrochloride, chlorpheniramine maleate, and dextromethorphan hydrobromide, in a tablet formulation. A diode array spectrophotometer, capable of multicomponent analysis, was used for the quantitation. The utility of this method was demonstrated in two ways: the analysis of a chewable pediatric tablet (formulation CP) containing 7.5 mg of pseudoephedrine hydrochloride, 0.5 mg of chlorpheniramine maleate, and 2.5 mg of dextromethorphan hydrobromide, and the dissolution analysis of a hydroxypropyl methylcellulose-based sustained-release tablet (formulation SR) containing 120 mg of pseudoephedrine hydrochloride, 8 mg of chlorpheniramine maleate, and 60 mg of dextromethorphan hydrobromide. The sensitivity of this assay is 7.5 micrograms/mL for pseudoephedrine hydrochloride, 1.0 micrograms/mL for chlorpheniramine maleate, and 5.0 micrograms/mL for dextromethorphan hydrobromide, using the second-derivative spectra of the absorbance with respect to wavelength. Determinations were made in 0.1 M sodium acetate buffer at pH 5.0 using a 1-cm quartz cell. Absorbance spectra, and their first and second derivatives, from 240 to 300 nm were used for the determination. The results obtained by this method compared favorably with the results obtained by a validated HPLC method.

Ultrasonically mediated solute permeation through polymer barriers.

The effects of ultrasound on the permeation of benzoic acid through polydimethylsiloxane, and hydrocortisone through cellulose was investigated. Ultrasonic irradiation resulted in a 23% increase in the permeability coefficient of hydrocortisone in a cellulose film. A 14% increase in permeability coefficient was observed for benzoic acid in a polydimethylsiloxane film. The effects of ultrasound on stagnant aqueous diffusion layers, membrane-solution interfacial temperature, membrane integrity, and diffusant stability were investigated. These factors were not responsible for the observed increases in permeability.