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Biomedical subjects

R L Hagan

Publications and source records attributed to R L Hagan.

12 recordsLinked to original sources
PubMed1997

Stability of ursodiol 25 mg/mL in an extemporaneously prepared oral liquid.

The stability of ursodiol in an extemporaneously formulated oral liquid was studied. A suspension was prepared by combining the contents of commercially available 300-mg capsules of ursodiol with glycerin, Ora-Plus (Paddock Laboratories), and orange syrup. A second formulation was prepared by combining ursodiol capsules with sterile water for irrigation. The final concentration of ursodiol in each formulation was 25 mg/mL. Six samples of each preparation were stored in 4-oz amber plastic prescription bottles protected from light. Three were stored at 22-23 degrees C and three were refrigerated at 2-6 degrees C. Immediately after preparation and at 7, 15, 30, 45, and 60 days, samples were obtained and frozen until assay by high-performance liquid chromatography. On day 60 the mean percentage of the initial ursodiol concentration remaining was 108.4% for the suspension stored at room temperature and 103.3% for the refrigerated suspension. The ursodiolin-water formulation was not analyzed because of rapid settling of ursodiol. Ursodiol 25 mg/mL in an oral liquid prepared extemporaneously from capsules and sweetened vehicle was stable for 60 days when stored in amber plastic bottles at 22-23 and 2-6 degrees C. Addition of ursodiol powder to water without a suspending agent resulted in a liquid formulation with a high variability in content uniformity.

Cholagogues and Choleretics↗
PubMed1997

Increasing urinary cotinine concentrations at elevated temperatures: the role of conjugated metabolites.

The presence of cotinine, a nicotine metabolite, in urine above a specified cutoff concentration is commonly used to distinguish smokers from nonsmokers, as in smoking cessation studies. A stability study of cotinine in urine was carried out after questions arose concerning analyte stability at elevated storage and shipment temperatures. Aliquots from a smokers urine pool were stored at 5, 25, 40, 50 and 60 degrees C for 30 days. Another set of aliquots, obtained by diluting the smokers pool 1:1 with nonsmokers urine, were stored under the same conditions. Free cotinine levels, determined by a stability-indicating gas chromatographic/mass spectrometric (GC/MS) assay, increased over the 30-day period at higher storage temperatures. Cotinine concentrations in the aliquots stored at 60 degrees C, for example, nearly doubled over 30 days (1301 to 2476 ng/ml), with similar proportional increases observed in the aliquots diluted with nonsmokers urine. Since cotinine can be excreted to a large degree as cotinine-N-glucuronide, this conjugated metabolite was determined by an indirect method. As the storage temperature increased, the free/conjugated cotinine ratio dramatically increased, pointing to cotinine-N-glucuronide as the source of the additional free cotinine at the higher storage temperatures. The results of this study are of much practical importance, since urine samples with free cotinine concentrations just below a cutoff value may become positive for smoking status if suitably low temperatures cannot be maintained during sample handling and shipment.

Chromatography, Gas↗
PubMed1997

Urinary 5-hydroxytryptophol following acute ethanol consumption: clinical evaluation and potential aviation applications.

HYPOTHESIS: The unknown prevalence of alcohol use and misuse among aviation pilots, crewmembers and associated support personnel call for continuous improvement of methods for detecting recent alcohol use. Early detection is essential to proper treatment and prevention of potentially catastrophic mishaps. Urinary 5-hydroxytryptophol (5HTOL), a serotonin (5HT) metabolite, has shown promise in the clinical setting as a noninvasive marker of recent alcohol consumption. METHODS: The urinary 5HTOL concentrations of 11 male and female subjects were followed for approximately 24 h following dosing with ethanol 0.6 g.kg-1. Concentrations were reported as a ratio of 5HTOL to 5-hydroxy-indoleacetic acid (5HIAA), 5HTOL/5HIAA (pmol/nmol), to compensate for urinary dilution and elevated 5HTOL levels due to dietary intake. Data from one male subject was excluded after he admitted to continued alcohol consumption subsequent to dosing and missing several urine samples. RESULTS: 5HTOL/5HIAA ratios remained above the 15 pmol/nmol cutoff for recent alcohol use for approximately 11-16 h in all except one subject. Calculations based on body weight and administered alcohol dose suggest that measurable blood alcohol levels would exist for only 5-7 h post ingestion. CONCLUSION: This study confirmed the extended elevation of 5HTOL/5HIAA ratios observed in earlier studies, even at the relatively low alcohol dose used herein. 5HTOL appears to be a marker for acute alcohol consumption worthy of further investigation by military and civilian authorities. Potential aviation applications of 5HTOL include validation of measurable blood alcohol concentrations, investigation of poor performance due to hangover effects, and as a forensic toxicology tool in aircraft accident investigations to distinguish between actual alcohol ingestion and post-mortem alcohol synthesis.

Acute Disease↗
PubMed1995

Studies on the antitumor effects of analogues of 5,8-dideazaisofolic acid and 5,8-dideazaisoaminopterin.

Six new analogues of 5,8-dideazaisofolic acid and 5,8-dideazaisoaminopterin were synthesized in an effort to obtain enhanced antitumor activity. The modifications included the replacement of the 2-amino group by hydrogen or methyl as well as the inclusion of a methyl substituent at position 9. Based upon activity against L1210 leukemia cells in culture, three of the new analogues together with one compound described previously were evaluated for cytotoxicity in vitro using three human tumor cell lines (Colo 320 DM, Hep G2 and HL-60). The most effective compound was 2-desamino-N9-methyl-5,8-dideazaisoaminopterin (2c) with the HL-60 cells being the most sensitive to its cytotoxic effects. These analogues were evaluated in vitro as inhibitors of dihydrofolate reductase (DHFR) and thymidylate synthase (TS) from human as well as bacterial (Lactobacillus casei) sources. All four of the 4-amino analogues were most effective toward L. casei DHFR compared with human DHFR, with 2-desamino-2-methyl-5,8-dideazaisoaminopterin (2d) and its 9-methyl derivative (2e) having 818- and 430-fold greater selectivity (L. casei/human). Most of the compounds studied were found to be only modest inhibitors of human TS (I50 values = 1.5 to 20 microM) and were therefore at least 40-fold less inhibitory than 10-propargyl-5,8-dideazafolic acid. Nevertheless, reversal of cytotoxicity studies with thymidine, hypoxanthine and folinic acid using the HL-60 cell line suggested that TS is the primary target for these analogues.

Aminopterin↗
PubMed1994

High-performance liquid chromatography for small-scale studies of drug stability.

The fundamentals of high-performance liquid chromatography (HPLC), as applied in small-scale studies of drug stability, are presented. Chromatography is the separation of a complex mixture into its individual compounds through partitioning between a mobile phase and a stationary phase. A high-performance liquid chromatograph consists of mobile-phase reservoirs, pumps, a mixer to mix the solvents, a valve into which the sample is injected, a guard column, a column containing the stationary phase, a detector, and a recorder. Once compounds have been separated in the column, they pass into the detector, where an electronic signal corresponding to the amount of compound present is recorded as a peak in a chromatogram. The most common detection method is ultraviolet and visible light spectroscopy. Key concepts in HPLC theory are retention time, the time from injection of the sample to detection of a peak; capacity factor, a measure of retention corrected for the elution of an unretained compound; resolution, a measure of how well two peaks are separated; the selectivity of the method; efficiency, or resolving power; and the degree of symmetry of the peaks produced. Most HPLC separations are performed in the reverse-phase mode, which involves a nonpolar stationary phase and a largely polar mobile phase. Other modes are normal phase, ion exchange, and size exclusion. Before a drug stability study is carried out, an HPLC method must be developed that suits the needs of the proposed experiment. A thorough literature search is essential. Literature procedures serve as useful starting points but may require a great deal of manipulation. After the HPLC separation has been performed, it is necessary to validate the method used. It must be proved that the method is stability indicating, that the chromatographic standards were properly prepared, that the standard curve is acceptable, and that the method is both precise and accurate. Pharmacists who ensure that reliable, reproducible HPLC methods are used throughout studies of drug stability will obtain sound data that may be of great value in pharmacy practice.

Chromatography, High Pressure Liquid↗
PubMed1991

Studies on the mechanism of antitumor action of 2-desamino-2-methyl-5,8-dideazaisofolic acid.

The new folate analogue, 2-desamino-2-methyl-5,8-dideazaisofolic acid, 2c, was synthesized and evaluated using a variety of biochemical and antitumor assays. For purposes of comparison, its 2-desamino, 2b, and 2-amino, 2a, counterparts, as well as N10-propargly-5,8-dideazafolic acid, 1a, and the corresponding 2-desamino, 1b, and 2-desamino-2-methyl, 1c, modifications were included in these studies. Compound 2c was found to be a potent inhibitor of the growth of L1210 and MCF-7 cells in culture, being only 2-fold and 5-fold less effective than 1c, respectively. However, although analogue 2c was 189-fold less inhibitory toward L1210 thymidylate synthase (TS) than 1c, its cytotoxicity was reversed completely by thymidine alone which suggests that the compound behaves as a TS inhibitor in cells. Enzymatically synthesized polyglutamates of 2c were substantially more inhibitory toward human TS than the parent compound. Compound 2c was the most efficient substrate for mammalian folyl-polyglutamate synthetase of the compounds studied having a Vmax/Km nearly 12-fold larger than 1c. Both 1c and 2c were effective inhibitors of the uptake of [3H]methotrexate into MOLT-4 cells, implying that each is efficiently transported into tumor cells. These results suggest that a weak inhibitor of TS in vitro can be a potent cytotoxic agent if it can readily gain entry into target cells and be converted to polyglutamated metabolites.

Animals↗
PubMed1989

Comparison of the biological effects of selected 5,8-dideazafolate analogues with their 2-desamino counterparts.

Three new 5,8-dideaza analogues of folic acid devoid of an amino group at position 2 have been prepared by using synthetic routes patterned after earlier methodologies. They were 2-desamino-5,8-dideazaisofolic acid, 2b, 2-desamino-10-thia-5,8-dideazafolic acid, 2c, and 2-desamino-10-oxa-5,8-dideazafolic acid, 2d. These compounds were found to be 4-6-fold more cytoxic toward L1210 leukemia cells than their 2-NH2 counterparts and to be poor inhibitors of mammalian thymidylate synthase. However, they were only 1.5-3-fold less inhibitory toward dihydrofolate reductase than the analogous compounds containing a 2-NH2 group. The known thymidylate synthase inhibitors 2-desamino-10-propargyl-5,8-dideazafolic acid and 10-propargyl-5,8-dideazafolic acid were included in this study for purposes of comparison.

Animals↗