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Biomedical subjects

L Chafetz

Publications and source records attributed to L Chafetz.

At least 19 recordsLinked to original sources
PubMed1994

Trace decomposition of selegiline. Use of worst-case kinetics for a stable drug.

A solution of selegiline hydrochloride reference standard, which contained no detectable impurities at the time of its preparation, was found by HPLC to contain a trace of a compound at the locus of methamphetamine when analyzed after 1 year. Heating selegiline solutions at pH 7 and 105 degrees C produced methamphetamine as the major product at a rate which closely followed the first-order rate equation. Using only these data and worst-case assumptions, rate constants were estimated at various temperatures; the activation energy was estimated to be about 25 kcal, and the stability-indicating validity of the assay used was reaffirmed. Selegiline undergoes degradation at a negligibly slow rate.

Chromatography, Gas↗
PubMed1991

Stability of diltiazem in acid solution.

A brief study of the stability of diltiazem was conducted at 70 degrees C in the pH range of 0.45 to 6.1 using polarimetry. Racemization did not occur. The hydrolysis rate of the acetate ester moiety was found to be slow, with a minimum in the pH-rate catenary at approximately pH 3.5. Where reaction products are known, photoelectric polarimetry has great advantages in speed, convenience, and cost compared with chromatographic methods for measuring rates of reaction of optically active analytes.

Diltiazem↗
PubMed1989

Issues in psychiatric caregiving.

This report presents descriptive data from a pilot investigation of 20 family caregivers to the psychiatrically disabled. Data were obtained through focused interviews with caregivers recruited from community organizations and clinical services. The model subject was a middle-aged mother caring for an adult child with schizophrenia. Qualitative analysis of interview data identified major concerns and support needs of individuals who assume this stressful role. Mental health nurses may assist caregivers to obtain support, reduce risks to their own well-being, and to promote well-being of the mentally ill.

Adult↗
PubMed1987

Phenolic cyclization of epinephrine, metaproterenol, metaraminol, phenylephrine, and terbutaline with formaldehyde.

An exploratory study of the rates of cyclization of the title compounds, all 3-hydroxyphenalkanolamines, with formaldehyde to 1,2,3,4-tetrahydroisoquinolines (THIQs) was performed using high-performance liquid chromatographic (HPLC) methods. Reactions occur quantitatively and practically instantaneously at room temperature and neutral pH; thus, rates were measured at acid pH. Cyclization occurs ortho or para to the 3-phenolic function, so that all but the 3,5-dihydroxyphenyl derivatives, metaproterenol and terbutaline, gave two THIQs. Terbutaline reacted significantly slower than the other compounds. Formaldehyde occurs in pharmaceutical systems and it serves as a model for other aldehydes that occur in sugars and flavors. The pharmaceutical implications of the reaction are discussed.

Cyclization↗
PubMed1981

High-pressure liquid chromatographic assay of theophylline, ephedrine hydrochloride, and phenobarbital tablets.

An innovation high-pressure liquid chromatographic method is described in which theophylline, ephedrine hydrochloride (measured as benzaldehyde), and phenobarbital are determined simultaneously with butabarbital as the internal standard. Chromatographic conditions were selected to afford a pH sufficient for rapid oxidation of ephedrine and relatively high UV absorbance for the barbiturates and a detection wavelength near the maximum for benzaldehyde and the barbiturates and the minimum for theophylline. Chromatograms show peaks from iodate, theophylline, phenobarbital, butabarbital, and benzaldehyde, in order of increasing retention time, all within the dynamic range of a conventional recorder. Procedures are provided for the assay of conventional and sustained-action tablet formulations.

Chromatography, High Pressure Liquid↗
PubMed1980

High-pressure liquid chromatographic assay of quinestrol tablets.

A specific assay for quinestrol was developed using high-pressure liquid chromatography. The estrogen was separated from tablet excipients on a chemically bonded hydrocarbon column utilizing acetonitrile-water as the mobile phase. Linearity studies were carried out using peak height measurements, and the detector response to the concentration of the steroid was confirmed. This procedure was rapid, accurate precise, and specific for the assay of the synthetic estrogen in the presence of formulation excipients and structurally similar estrogens.

Chromatography, High Pressure Liquid↗
PubMed1977

IR spectrophotometric assay of carbachol solutions.

Carbachol ophthalmic solutions can be assayed by evaporating a measured volume, dissolving the residue in methanol, and scanning the carbonyl stretching frequency in an IR spectrophotometer using a cell with calcium fluoride windows. Methylcellulose and other formulation vehicle components do not interfere. The method is stability indicating with respect to hydrolysis. It affords a recovery of 99.5+/-0.51% (RSD).

Carbachol↗
PubMed1977

Selective photometric determination of betamethasone benzoate and other 21-hydroxycorticosteroids.

Condensation of the glyoxal obtained by cupric acetate oxidation of 21-hydroxycorticosteroids with acetous phenylhydrazine reagent affords a near UV chromophore. All of the tested corticosteroids, including triamicinolone acetonide, which gives low color yields in the Porter-Silber reaction and its Lewbart-Mattox modification, gave similar absorption maxima (362-370 nm) and molar absorptivities (epsilon = 17,000-20,500). Since corticosteroid 21-esters and oxidation products do not undergo the reaction, the assay method based on it is stability indicating for betamethasone benzoate and the other test compounds. Procedures are described for the assay of two topical betamethasone benzoate preparations and hydrocortisone and prednisolone tablets; recovery and precision data are given.

Betamethasone↗