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Biomedical subjects

B N Swanson

Publications and source records attributed to B N Swanson.

53 records · Page 3Linked to original sources
PubMed1981

Biotransformation and biological activity of N-(4-hydroxyphenyl)retinamide derivatives in rodents.

The metabolism and bioactivity of N-(4-hydroxyphenyl)-all-trans-retinamide (HPR) and of various O-alkyl and ester derivatives of HPR were investigated in rodents. The principal metabolite of HPR in tissues is N-(4-methoxyphenyl)-all-trans-retinamide. N-(4-methoxyphenyl)all-trans-retinamide is equipotent to HPR in reversing keratinization of retinoid-deficient hamster trachea in vitro. Another nonpolar metabolite of HPR is also present in tissue and (although not positively identified) is thought to be a long-chain fatty acid ester of HPR. HPR is excreted into rat bile as numerous polar retinamides, including HPR-O-glucuronide. The rate of hydrolysis of HPR esters by rat serum and hepatic enzymes in vitro is inversely related to the length of the esterified acid side group. After a 30-min incubation at 37 degrees C in serum, percentage of hydrolysis for acetyloxy, propionyloxy, butyryloxy, pivaloyloxy and octanoyloxy esters of HPR is 41, 20, 7.5, 1.9 and 1.5, respectively. In contrast, hydrolysis by hepatic esterases is more rapid, particularly for the pivaloyloxy ester. Potency of the various HPR esters in the tracheal organ culture bioassay decreases as the length of the esterified side group increases; the acetyloxy ester is at least 5 times more potent than the octanoyloxy ester.

Animals↗
PubMed1981

Angiotensin converting enzyme activity in human serum: relationship to enzyme inhibitor in vivo and in vitro.

Quantitative relationships between angiotensin converting enzyme activity in human serum and concentration of an enzyme inhibitor, the active diacid metabolite of MK-421 [N-(S-1-carbethoxy-3-phenylpropyl)-S-alanyl-S-proline maleate], were defined. Dose-response curves were generated in vitro by adding the diacid metabolite (DM) to serum (ID50 = to 6x10-9 M); l0-15% of initial activity was nonsuppressible. DM an converting enzyme activity were also measured in serum from hypertensive subjects receiving oral MK-421. The dose-response curve for serum samples following single doses of MK-421 (ID50 = 6x10-9M), was similar to curves generated in vitro while the curve for sample following chronic therapy suggested a small decrease in inhibitory potency.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1979

The metabolism of floctafenin in man and rodents.

Floctafenin (FFn), 2,3-dihydroxypropyl--N--(8--trifluoromethyl--4--quinolyl) anthranilate, a new nonnarcotic analgesic drug, was studied in man, mice, and the isolated perfused rat liver. In all species the drug is rapidly hydrolyzed to floctafenic acid (FFa). In seven volunteer subjects who each received a single oral dose of 400 mg floctafenin on an empty stomach, the blood concentration of FFa usually reached a maximum between 1 and 2 hours (mean 1.57 +/- 1.28 microgram/ml at 1.5 hours) and declined over the next 6 hours. Eight hours after drug administration the mean concentration of FFa in the blood of the volunteers was 0.1 +/- .05 microgram/ml. Approximately 25 per cent of the administered dose of floctafenin was recovered as FFa and hydroxy-FFa in the urine collected from each subject for 48 hours after drug administration. In mice each having received a single intraperitoneal dose of floctafenin (2 mg), the concentration of floctafenin declined by about 50 per cent in 15 minutes, and this decline was accompanied by a rise in the concentration of FFa that remained constant for 3 hours. The analgesic effect observed after administration of floctafenin to humans is likely to be mediated by its major metabolite, FFa. In these volunteers no free floctafenin was detected in the blood.

Adult↗
PubMed1978

Excretion of valproic acid into semen of rabbits and man.

Dipropylacetic acid (VPA, valproic acid) has been quantified in plasma and semen from rabbits and man using a new gas-liquid chromatographic assay. The drug assay is rapid, sensitive and free from interference by VPA metabolites. The beta phase half-life of VPA in rabbits after an i.v. dose (50 mg/kg) was 56 +/- 6 min. The concentration of VPA in rabbit plasma was 17 to 30 times the concentration in rabbit semen. In man, 500 mg doses of the free acid, p.o., resulted in VPA concentrations in plasma that were 11 to 17 times the concurrent levels in semen. VPA, in concentrations up to 10(-3) M, did not influence the motility of rabbit spermatozoa in vitro.

Adult↗
PubMed1978

Seminal excretion, vaginal absorption, distribution and whole blood kinetics of d-methadone in the rabbit.

The disposition of 40 mg of d-methadone HCl was studied in New Zealand White rabbits. After an intravenous infusion to male rabbits, the beta phase half-life was 106 +/- 21 min and the apparent volume of distribution was 12.6 liters/kg b.w. After an i.m. injection, the peak drug concentration in arterial blood (1.02 microgram/ml) occurred 10 min after the injection, whereas the peak concentration in semen (2.58 microgram/ml) occurred 140 min later. The semen/blood drug concentration ratio was 6.8 at 150 min after the injection. The concentration of d-methadone was measured in blood, spleen, liver, lung, prostate, seminal vesicle, testis and heart 130 minutes after an i.m. dose. All tissues had drug levels that exceeded the concentration in blood (0.42 microgram/ml). The concentrations in lung (33.5 microgram/g), kidney (15.2 microgram/g) and spleen (30.6 microgram/g) were particularly elevated. After intravaginal implantation, d-methadone was rapidly absorbed into the systemic circulation of female rabbits; the peak drug level in blood (0.94 microgram/ml) occurred 60 min after drug administration.

Absorption↗
PubMedDate not supplied

Comparative antihypertensive effects of enalapril maleate and hydrochlorothiazide, alone and in combination.

Enalapril maleate is an investigational oral prodrug whose hydrolyzed diacid metabolite is a potent angiotensin-converting enzyme inhibitor. Fourteen patients with mild to moderate hypertension were evaluated after receiving placebo, and two weeks of treatment with each of the following: enalapril maleate (20 mg b.i.d.), hydrochlorothiazide (25 mg b.i.d.), and the two in combination. In comparison to placebo, the magnitudes of the blood pressure reduction after enalapril and hydrochlorothiazide alone were comparable. The reduction in blood pressure following enalapril was evident throughout the 12-hour dosing interval. The combination of enalapril and hydrochlorothiazide resulted in a marked further reduction in blood pressure that was greater than that predicted from the responses to the individual drugs (P less than 0.05). Biochemical parameters confirmed inhibition of angiotensin-converting enzyme during enalapril treatment; serum angiotensin-converting enzyme activity proved an excellent monitor of compliance. Enalapril was generally well tolerated. Adverse effects included symptomatic hypotension in three patients when enalapril was first added to hydrochlorothiazide and hyperesthesia of the oral mucosa without a loss of taste in one patient on enalapril. Enalapril maleate alone and especially in combination with hydrochlorothiazide appears to be an effective, well-tolerated converting enzyme inhibitor with at least a 12-hour duration of action.

Adult↗
PubMedDate not supplied

Methyldopa does not alter the disposition of digoxin.

To investigate whether methyldopa alters digoxin disposition, eight healthy subjects received methyldopa titrated to 250 mg t.i.d. or placebo in a double-blind, cross-over manner for 16 consecutive days, with 0.25 mg intravenous digoxin coadministered on day 5 and 0.25 mg oral digoxin on days 9 to 16. Digoxin concentrations in plasma and urine were measured by RIA. Although assay sensitivity did not allow an adequate assessment of serum AUC(0-infinity) after intravenous administration, mean digoxin AUC(0-24) was 10.2 +/- 3.5 and 10.0 +/- 1.8 ng/ml X hr with placebo and methyldopa, respectively (P greater than 0.05). Mean urinary excretion after digoxin with or without methyldopa treatment was 0.204 +/- 0.34 and 0.197 +/- 0.38 mg, respectively. The mean steady-state serum concentrations of oral digoxin (AUC(0-24)/zeta) with and without methyldopa were 0.65 +/- 0.2 and 0.62 +/- 0.3 ng/ml, respectively. These data revealed no significant differences (P greater than 0.05) for various parameters with power of greater than 0.8 to detect meaningful differences of approximately 30 per cent. Thus, methyldopa did not alter digoxin disposition in healthy subjects, and a pharmacokinetic interaction in patients is unlikely.

Administration, Oral↗
PubMedDate not supplied

Indacrinone: natriuretic and uricosuric effects of various ratios of its enantiomers in healthy men.

Indacrinone is an investigational loop-acting diuretic. To evaluate the natriuretic and uricosuric effects of varying ratios of its enantiomers, 10 healthy men, on a controlled Na+ (100 mEq) and K+ (80 mEq) diet, participated in a double-blind, randomized, balanced incomplete block, multiple-dose (one week) study of a fixed daily dose (10 mg) of (-) enantiomer combined with increasing doses (40, 90 and 140 mg) of (+) enantiomer versus 50 mg hydrochlorothiazide and placebo. On day 1, mean 24-h urinary Na+ increased (p less than 0.01) comparably (approximately 285 mEq) after each enantiomer combination and hydrochlorothiazide; however, the enantiomer combinations had marked uricosuric and hypouricemic effects that were enhanced with increased (+) enantiomer doses. By day 7, while enantiomer combinations and hydrochlorothiazide demonstrated comparable natriuretic activity, mean serum uric acid levels (mg/dl), in comparison to placebo, were increased (p less than 0.05) with hydrochlorothiazide but progressively decreased with increases in (+) enantiomer. Thus varying the ratio [(+, uricosuric): (-, natriuretic)] of the enantiomers of indacrinone caused natriuresis similar to hydrochlorothiazide, but had an opposite effect on serum uric acid.

Adult↗
PubMedDate not supplied

Steady-state disposition of diflunisal: once- versus twice-daily administration.

To evaluate the steady-state bioequivalence of the nonsteroidal antiinflammatory analgesic agent, diflunisal, administered once versus twice daily, 13 healthy volunteers received diflunisal as follows: 1000 mg at 8:00 AM and 500 mg at 8:00 AM and 8:00 PM, each for 14 days in a randomized crossover study. The mean (+/- SD) steady-state peak plasma concentrations were significantly greater after once-daily dosing (186 +/- 25 micrograms/ml vs 150 +/- 37 micrograms/ml; p less than 0.01). The time to peak concentration was also longer after the single-dose regimen (2.5 +/- 0.8 vs 1.9 +/- 0.9 hr; p less than 0.05). The regimens were similar with respect to the mean 24-hour area under the plasma concentration-time curve at steady state (2839 +/- 612 vs 2782 +/- 778 micrograms.hr.ml-1), steady-state plasma concentrations (118 +/- 25 vs 116 +/- 32 micrograms/ml), trough plasma concentration (85 +/- 27 vs 92 +/- 28 micrograms/ml) as well as 24-hour urinary excretion (776 +/- 79 vs 771 +/- 89 mg) of diflunisal. Based on urinary recoveries, the bioequivalence ratio (once vs twice daily) was 1.01 +/- 0.08. These results indicate that diflunisal administered once daily might offer comparable therapeutic effects but be more convenient than a twice-daily regimen.

Adult↗
PubMedDate not supplied

Inhibition of sulindac metabolism by dimethyl sulfoxide in the rat.

Dimethyl sulfoxide (DMSO) suppresses conversion of the prodrug sulindac to its bioactive sulfide metabolite (SD) by competitively inhibiting sulfoxide reductase. During continuous iv infusions of sulindac (1 mg/kg X h), plasma concentrations of SD at steady-state equilibrium were 80% lower when DMSO was infused concomitantly at 0.34 ml/kg X h, whereas sulindac plasma concentrations were not significantly affected by DMSO. Dermal application and intragastric administration of DMSO also inhibited SD accumulation in plasma. DMSO was only a weak inhibitor of SD oxidation in vitro and did not affect the rate of SD elimination in vivo. In contrast, dimethyl sulfide, a metabolite of DMSO, was a potent inhibitor of SD oxidase in vitro. These data suggest that DMSO can inhibit bioactivation and, hence, the antiinflammatory effects of sulindac.

Administration, Oral↗
PubMedDate not supplied

Excretion of phenytoin into semen of rabbits and man. Comparison with plasma levels.

The concentration of phenytoin (diphenylhydantoin, DPH) was measured in plasma and semen of rabbits and man. In the rabbit, a single iv injection of DPH (4.64 mg) resulted in a concentration-time curve for DPH in semen parallel to the concentration-time curve for DPH in plasma (t1/2beta = 171 +/- 29 min). A semen/plasma drug concentration ratio of 0.20 was maintained for at least 8 hr, demonstrating that DPH concentrations in semen are directly proportional to DPH concentrations in plasma. In epileptic subjects maintained on oral DPH the mean drug concentration in semen was 2.31 microgram/ml while that in plasma was 13.8 microgram/ml. The mean semen-plasma DPH concentration ratio in man was 0.17; this closely approximates the observed ratio in rabbits.

Adult↗
PubMedDate not supplied

Medical use of dimethyl sulfoxide (DMSO).

DMSO is a clear odorless liquid, inexpensively produced as a by-product of the paper industry. It is widely available in the USA as a solvent but its medical use is currently restricted by the FDA to the palliative treatment of interstitial cystitis and to certain experimental applications. Cutaneous manifestations of scleroderma appear to resolve (albeit equivocally) following topical applications of high concentrations of DMSO. A limited number of small clinical trials indicate that intravenous DMSO may be of benefit in the treatment of amyloidosis, possibly by mobilizing amyloid deposits out of tissues into urine. Dermal application of DMSO seems to provide rapid, temporary, relief of pain in patients with arthritis and connective tissue injuries. However, claims for antiinflammatory effects or acceleration of healing are currently unwarranted. There is no evidence that DMSO can alter progression of degenerative joint disease, and, for this reason, DMSO may be considered for palliative treatment only and not to the exclusion of standard antiinflammatory agents. The safety of DMSO in combination with other drugs has not been established; neurotoxic interactions with sulindac have been reported. In experimental animals, intravenous DMSO is as effective as mannitol and dexamethasone in reversing cerebral edema and intracranial hypertension. An initial clinical trial in 11 patients tends to support this latter application. DMSO enhances diffusion of other chemicals through the skin, and, for this reason, mixtures of idoxuridine and DMSO are used for topical treatment of herpes zoster in the UK. Adverse reactions to DMSO are common, but are usually minor and related to the concentration of DMSO in the medication solution. Consequently, the most frequent side effects, such as skin rash and pruritus after dermal application, intravascular hemolysis after intravenous infusion and gastrointestinal discomfort after oral administration, can be avoided in large part by employing more dilute solutions. Most clinical trials of DMSO have not incorporated the components of experimental design necessary for objective, statistical evaluation of efficacy. Randomized comparisons between DMSO, placebo and known active treatments were rarely completed. Final approval of topical DMSO for treatment of rheumatic diseases in particular will require a multi-center, randomized comparison between high and low concentrations of DMSO and an orally-active, nonsteroidal antiinflammatory agent.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Pharmacokinetics of N-(4-hydroxyphenyl)-all-trans-retinamide in rats.

The concentration of N-(4-hydroxyphenyl)-all-trans-retinamide (HPR) was determined in plasma and a variety of tissues from rats after an intravenous dose (5 mg/kg). The plasma concentration-time curve could be accurately described by a triexponential equation. The apparent volume of distribution of HPR was approximately 10-12 liter/kg and the terminal half-life was 12 hr. Metabolites of HPR were more abundant than intact drug in most tissues 24 hr after the iv dose. A 5-day excretion study with radiolabeled HPR revealed that less than 2% of a single iv dose (5 mg/kg) is excreted as unmetabolized HPR in urine and feces and that most of the radioactivity is eliminated in the feces. HPR was incompletely absorbed after an oral dose (10 mg/kg).

Animals↗
PubMedDate not supplied

Effect of dimethyl sulfoxide on sulindac disposition in rats.

Sulindac and dimethyl sulfoxide (DMSO) are both effective antiinflammatory agents in man. Since the sulfoxide moiety in these compounds is metabolized similarly, a biochemical interaction between the two drugs in vivo was thought to be possible. After iv injections of sulindac (5 mg/kg), plasma concentrations of sulindac, and its sulfide and sulfone metabolites, were measured in normal rats and in rats that had received, 30 min earlier, a single ip dose of DMSO (0.1, 0.5, or 1.0 ml). The half-life of sulindac (normally 94 min) was increased significantly by DMSO (0.1, 0.5, or 1.0 ml). The half-life of sulindac (normally 94 min) was increased significantly by DMSO (408 min after 1.0 ml of DMSO). Plasma sulfide metabolite levels were reduced in a dose-related manner by DMSO (93% reduction in peak concentration after 1.0 ml of DMSO). Sulfone metabolite concentration was also significantly diminished by the highest dose of DMSO. Similarly, DMSO was shown to decrease conversion of sulindac to sulfide and sulfone metabolites by rat liver enzymes in vitro. Sulfoxide reductase was more sensitive to DMSO inhibition than was sulfoxide oxidase both in vivo and in vitro. These data demonstrate that DMSO can significantly alter in vivo the formation of the pharmacologically active, sulfide metabolite of sulindac; therefore, concurrent use of DMSO and sulindac should be approached with caution.

Animals↗