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Biomedical subjects

T R Bates

Publications and source records attributed to T R Bates.

At least 37 records · Page 2Linked to original sources
PubMed1977

Gastrointestinal absorption of griseofulvin from corn oil-in-water emulsions: effect of amount of corn oil ingested in man.

The effect of the amount of emulsified corn oil ingested on the gastrointestinal absorption of griseofulvin in man was assessed after oral administration of 5, 10, 15, or 30 gm doses of a corn oil (40% w/w)-in-water emulsion dosage form, each containing 250 mg of microsize griseofulvin. For comparison, griseofulvin absorption from two-125 mg commercial tablets of ultramicrosize drug dispersed in polyethylene glycol 6;000 was also determined. Griseofulvin was almost completely absorbed from the microsize drug emulsions and ultramicrosize drug tablets, whereas 50% of an oral dose is absorbed from commercial microsize griseofulvin tablets. Only 4 gm of emulsified corn oil (as a 10-gm dose of emulsion) is required to maximize the uniformity and extent of griseofulvin absorptions. The emulsion dosage form is uniquely suited for pediatric use.

Absorption↗
PubMed1976

The influence of food on nitrofurantoin bioavailability.

The effect of food on the absorption of five commercial dosage forms of nitrofurantoin varying widely in drug release and dissolution characteristics was assessed in man after oral administration. Four healthy fasting and nonfasting male subjects received, in a crossover fashion, a single 100-mg dose of microcrystalline nitrofurantoin as an aqueous suspension, three different compressed tablets, and a single 100-mg dose of macrocrystalline nitrofurantoin in a capsule. Both the absorption and the duration of therapeutic urinary concentrations of nitrofurantoin were significantly increased after administration of the five products to nonfasting subjects. The enhancement in the bioavailability of the drug in the presence of food ranged from 20% to 400%, with the greatest absorption-enhancing effect occurring with those dosage forms exhibiting the poorest dissolution characteristics. It is concluded that single-dose comparative bioavailability studies of drug products normally administered with food should be performed in both nonfasting and fasting subjects.

Adult↗
PubMed1976

Warfarin.

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Biological Availability↗
PubMed1976

Cholestyramine-induced inhibition of salicylazosulfapyridine (sulfasalazine) metabolism by rat intestinal microflora.

The effect of multiple oral administration of the hypocholesterolemic agent cholestyramine (a strongly basic anion-exchange resin) on the metabolism of salicylazosulfapyridine by microflora present in the colon and cecum was assessed in conventional rats by following the time course of salicylazosulfapyridine and its metabolites in the urine and feces. The intestinal metabolism of salicylazosulfapyridine (a single 100 mg/kg oral dose), which involves reduction of the azo linkage by bacterial azo reductases and the liberation of sulfapyridine and 5-aminosalicylic acid (potential active metabolites of the drug), was markedly inhibited by the resin (250 mg/kg oral doses at -2, +2 and +6 hours), resulting in an enhanced fecal excretion of intact salicylazosulfapyridine. The existence of a rank-order correlation between the in vitro binding of salicylazosulfapyridine, sulfapyridine and 5-aminosalicylic acid to the resin and their fecal excretion pattern in resin-treated animals suggests that a direct cholestyramine-salicylazosulfapyridine interaction occurred within the intestinal tract and that in the bound state, the azo bond of the drug was inaccessible to bacterial azo reductases. These findings suggest that chronic oral administration of cholestyramine to patients with ulcerative colitis who are receiving salicylazosulfapyridine could result in a significant reduction in the absorption and metabolism of the drug and hence, in its therapeutic efficacy.

Aminosalicylic Acids↗
PubMed1976

Time course of free and N4-acetylated sulfapyridine concentrations in the plasma and saliva of man after sulfasalazine (salicylazosulfapyridine) administration: preliminary findings.

The time course of free and N4-acetylated sulfapyridine (SP) concentrations in the saliva and whole plasma was determined in a healthy male volunteer after a single 2.0 g oral dose of salicylazosulfapyridine (SASP) as four-500 mg commercial, uncoated tablets. The mean (+/- S.D.) plasma: saliva concentration ratios for free and acetylated SP was 2.04 (+/- 0.24) and 3.12 (+/-0.43), respectively, and were independent of plasma concentration and saliva pH. The elimination half-lives of SP and N4-acetyl SP could be determined from either salivary or plasma concentration-time data. These preliminary results suggest that measurement of saliva concentrations of free and acetylated SP may be a convenient, noninvasive method for monitoring indirectly the plasma concentrations of SP and acetyl SP in patients treated with SASP and for determining acetylator phenotype.

Acetates↗
PubMed1975

Bioavailability of micronized griseofulvin from corn oil-in-water emulsion, aqueous suspension, and commercial tablet dosage forms in humans.

The purposes of this investigation were to determine and to compare the oral absorption characteristics of micronized griseofulvin (500 mg) after its administration to humans in the form of a corn oil-in-water emulsion containing dispersed drug, an aqueous suspension, and two different commercial tablets (A and B). The four dosage forms were administered in a random crossover fashion to five fasting subjects, and drug absorption was assessed from urinary excretion data for the major metabolite of the antibiotic (6-desmethylgriseofulvin). The drug was most rapidly, uniformly, and completely absorbed from the corn oil-in-water emulsion. As compared to either the aqueous suspension, Tablet A, or Tablet B, three- to fourfold increases in the maximum body levels and a twofold enhancement in the bioavailability of the antibiotic were observed after administration of the emulsion dosage form. A mechanism based on the ability of the linoleic and oleic acids liberated during the digestion of corn oil to inhibit GI motility and stimulate gallbladder evacuation may explain the marked enhancing effect of emulsified corn oil on griseofulvin absorption in humans. This new lipid-in-water emulsion dosage form of micronized griseofulvin appears to offer several clinical advantages in the treatment of fungal infections.

Adult↗
PubMed1975

Apparent absorption kinetics of micronized griseofulvin after its oral administration on single- and multiple-dose regimens to rats as a corn oil-in-water emulsion and aqueous suspension.

This investigation was designed to quantitate and compare in the rat the oral absorption characteristics of micronized griseofulvin from a corn oil-in-water emulsion dosage form containing suspended drug and a control aqueous suspension after single-dose (50 mg/kg) and multiple-dose (50 mg/kg every 12 hr for five doses) administrations. The time course of intact drug in the plasma of all animals was best described by a one-compartment open model with apparent zero-order absorption. In contrast to that observed with the aqueous suspension, the onset of drug absorption after single-dose administration of the corn oil emulsion was significantly delayed. This difference disappeared upon multiple dosing of the two dosage forms, with the mean onset being quite rapid in both cases. Administration of a single dose of the antibiotic as the corn oil emulsion resulted in considerable increases in the maximum plasma levels of griseofulvin and in the duration, relative extent, and uniformity of drug absorption compared to those observed after administration of the control aqueous suspension. The potentiating effects of the lipid on drug absorption persisted on multiple dosing but at a somewhat reduced level.

Administration, Oral↗
PubMed1975

The effect of natural and surgically constructed aortopulmonary shunts on hemodynamic function in tetralogy of Fallot.

A hemodynamic model has been developed for the patient with tetralogy of Fallot. Equations representing the circulatory flow pattern and oxygen balance in this disease were incorporated into a computer program. With the computer model it is possible to simulate the effect of natural and surgically constructed aortopulmonary shunt flow on hemodynamic function in tetralogy of Fallot. Graphic representations of the computer output are presented which show how aortopulmonary shunt flow influences the physiology of exercise and hypoxic episodes. An explanation is advanced for the lack of correlation between resting arterial oxygen saturation and the incidence of hypoxic episodes. The model demonstrates the effect of surgical aortopulmonary shunts in eliminating hypoxic spells.

Aorta↗
PubMed1975

Nitrofurantoin.

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Biological Availability↗
PubMed1975

Comparative bioavailability of anhydrous griseofulvin and its chloroform solvate in man.

Using a crossover experimental design, the absorption profile of griseofulvin was assessed in human volunteers after oral administration of a 500 mg dose of the antifungal antibiotic as capsules of the anhydrous (nonsolvated)-and monochloroform solvate forms of the drug. The maximum body level of drug and the rate and extent of griseofulvin absorption (or bioavailability) were significantly increased after administration of the chloroform solvate as compared to that observed after administration of the nonsolvated form of the drug. The enhanced absorption of griseofulvin chloroformate correlated well with its enhanced solubility and dissolution rate at 37 degrees C in simulated intestinal fluid (20 mM sodium deoxycholate, pH 7.5). This is the first demonstration of a drug-organic solvate displaying improved gastrointestinal absorption characteristics over the anhydrous form of a drug.

Biological Availability↗