We have studied the effect of various absorption promoters on the percutaneous absorption dynamics of 6-carboxyfluorescein (CF) which is a poorly absorbable drug. The absorption of CF was determined by fluorescence photographic image since (CF) emits a strong light yellow fluorescence. The co-administration of sodium dodecylsulfate (SDS) and 2-mercaptoethanol (MER), the pretreatment with calcium thioglycolate and the coadministration of Azone[○!R](AZ) and surfactant (HCO-60) were used to promote the absorption of CF. We have also studied the injury of skin tissue by the absorption promoters. The fluorescence photographic image of rat skin, after the co-administration of SDS and MER and after the co-administration of AZ and HCO-60 were similar to the image with the stratum corneum removed from the skin. These absorption promoters did not affect the histological nature of the rat skin tissue and the recovery experiment showed no injurious effect by these absorption promoters to the skin tissue.

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The effect of probenecid on the plasma kinetics of sulfamonomethoxine (SMM) was examined in conscious pigs. A linear kinetic dose of SMM (10 mg/kg) was injected with or without probenecid. Probenecid (25 mg/kg, i.v.) was injected immediately before SMM injection and against at 1, 2, 3, 4 and 6 h later. The AUCs of SMM and of the acetylated compound of SMM (AcSMM) in probenecid injected animals were significantly larger when compared with those of non-injected animals (p<0.05). Next, possible active secretion from the renal tubule of SMM and its metabolites was examined using probenecid and pyrazinoate. Ten commercial pigs with ureter cannulae were used under anesthesia. The plasma concentration of SMM and AcSMM was maintained at a steady state by a priming dose of SMM (5 mg/kg, i.v.) followed by sustaining inusion (4 μg/kg/min). Renal clearance of AcSMM was suppressed by bolus injection of probenecid (25 mg/kg), but that of SMM was not. The renal excretion of a water soluble metabolite was suppressed by probenecid. No marked changes in renal excretory kinetics were found by pyrazinoate injection (12.5 mg/kg, i.v.). Consequently, the saturation in the active tubular secretion of AcSMM may play an important role in the nonlinear pharmacokinetics of SMM in pigs.

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Interactions between methamphetamine and quinine were studied using two different tests. The duration and intensity of methamphetamine-induced stereotyped behavior was enhanced by pretreatment of rats with quinine. Pretreatment of rats with SKF-525 A and CCl₄ also resulted in the enhancement of methamphetamine-induced stereotyped behavior. Pretreatment with phenobarbital shortened the stereotypy evoked by methamphetamine. Furthermore, urinary excretion patterns of methamphetamine and its metabolites were determined following the administration of the drug to rats which had been pretreated with certain drugs. Quinine, SKF-525 A and CCl₄ inhibited the urinary excretion of p-hydroxylated metabolites and increased the excretion of the unchanged methamphetamine and amphetamine. These results strongly suggest that the enhancement of methamphetamine-induced stereotyped behavior in the rats pretreated with quinine, SKF-525 A and CCl ₄ could be ascribed to the inhibition of the p-hydroxylation reaction of methamphetamine and thus may lead to the increased concentration and pharmacological effect of the drug.

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Chronic effects of highly purified eicosapentaenoic acid (EPA) on systolic blood pressure in spontaneously hypertensive rats (SHR) and normotensive rats were studied. Daily oral administration of 30 to 300 mg/kg EPA for eight weeks significatly decreased the development of hypertension in SHR dose-dependently. Eight weeks treatment of 30, 100, and 300 mg/kg EPA reduced mean systolic blood pressure by 23, 29, and 32 mmHg, respectively, compared to untreated rats. Hypotensive effect of EPA progressed slowly and was reversible after the termination of the treatment. However, daily administration of EPA to normotensive rats did not affect the systolic blood pressure. EPA may be useful as a hypotensive agent for treatment of hypertension.

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The binding of bovine serum albumin (BSA), containing ¹²⁵I-BSA, to isolated rat hepatocytes was studied over a 300-fold concentration range of BSA to characterize the interaction between albumin and the liver cells in albumin-mediated hepatic transport. The binding of BSA with a high affinity to the cell surface of hepatocytes was not found in the binding behavior. The bound fraction of BSA with hepatocytes was about 1% over those concentration range of BSA.

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Liver microsomal 7-alkoxycoumarin O-dealkylase activities in rats were stimulated by the administration of large doses of 5-[(2-aminoacetamide) methyl]-1-[4-chloro-2-(o-chlorobenzoyl) phenyl]-N, N-dimethyl-1 H-s-triazole-3-carboxamide hydrochloride dihydrate (450191-s), a new sleep inducer which is a 1 H-1, 2, 4-triazolyl benzophenone derivative. To obtain the correlation between the stimulation or induction of hepatic enzymes and the plasma level of the metabolites of 450191-S, various amounts of 450191-S were administered orally to rats and the metabolites in plasma were determined by high performance liquid chromatography. Plasma concentration-time profiles for metabolites in rats showed the appearance of metabolites in plasma followed by their rapid disappearance from blood when the animals received non-inducing amounts of 450191-S. On the other hand, the profiles of metabolites in rats administered higher amounts of the drug showed very high plasma concentrations of metabolites, especially 8-chloro-6-(2-chlorophenyl)-N-methyl-4 H-1, 2, 4-triazolo [1, 5-a][1, 4] benzo diazepine-2-carboxamide (M-2) and 8-chloro-6-(2-chlorophenyl)-N-hydroxymethyl-4 H-1, 2, 4-triazolo [1, 5-a][, 4] benzodiazepine-2-carboxamide (M-A), which were maintained for a long time with slow elimination. These results led to the conclusion that the induction of hepatic drug-metabolizing enzymes is closely correlated with the high plasma concentrations of metabolites and their prolonged existence in plasma.

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Effects of diltiazem on renal blood flow and renal function were studied under angiotensin II-loaded condition in anesthetized dogs. Intravenous infusion of angiotensin II at a rate of 0.25 μg/kg/min produced an increase in blood pressure by 30 to 40 mmHg and a decrease in renal blood flow by 30 to 40%, resulting in a 100% increase in renal vascular resistance. Under this condition, diltiazem exhibited a dose related increase in renal blood flow not only by intrarenal administration (1-30 μg/kg) but also by intravenous administration (10-200 μg/kg). The effect was greatly augmented, compared to that observed in a control angiotensin II-unloaded condition. Under angiotensin II-loaded condition, glomerular filtration rate and para-aminohippuric acid clearance, as well as renal blood flow, were markedly reduced, the levels of which were recovered by intrarenal administration of diltiazem (10 μg/kg/min) accompanied by marked natriuresis. The natriuretic effect of diltiazem was also observed by intravenous administration (100 μg/kg). It is suggested that the improving effects diltiazem on renal hemodynamics and ranal function, under angiotensin II-loaded condition, are mainly due to its inhibitory action on angiotensin II-evoked renal vasoconstriction, resulting from its calcium antagonistic action.

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We have designed a thermistor rectal probe thermometer for measuring the antipyretic activity of suppositories. Using this thermistor probe, we tested the antipyretic effect of an indomethacin suppository in comparison with oral and intravenous administrations in rabbits (male, 2.5-2.9 kg). The rectal temperature of normal rabbits remained unchanged after rectal and intravenous administration of indomethacin, 25 mg/body and 10 mg/kg, respectively. The antipyretic effect was tested in febrile rabbits injected with bacterial pyrogen, lipopolysaccharide (LPS) 0.2 μg/kg (i.v.). The dose-dependent antipyretic activities were observed in febrile rabbits administered with indomethacin by rectal (6.3-23.7 mg/body), intravenous (2.5-10 mg/kg) and oral (2.5-20 mg/kg) routes. When indomethacin was administered simultaneously or 1 h after LPS, the most potent antipyretic effect was observed in the case of rectal administration and the weakest effect was observed in that of oral administration. These data indicate that the rectal administration of drugs can produce a potent antipyretic activity, not inferior to that of the intravenous injection.

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The mechanism of the antipyretic effect of indomethacin (IM) on fever induced by bacterial pyrogen (LPS, 0.2 μg/kg, i.v.), leukocytic pyrogen (LP, 2 ml/kg, i.v.) and 2, 4-dinitrophenol (DNP, 20 mg/kg, i.m.) in male adult rabbits was studied. In plasma, the biological half lives of IM in normal and LPS-injected rabbits were estimated to be 24 and 21 min in the early phase and 72 and 51 min in the late phase, respectively. A potent antipyretic effect was observed with intravenous injection of IM in LPS- and LP-induced fevers, but not in DNP-induced fever. The antipyretic effect was also observed with intracisternal injection of indomethacin at doses of 0.025 and 0.013 mg/kg. The activity of endogenous pyrogen in serum after LPS injection was not suppressed by the injection of IM (10 mg/kg, i.v.). The production of LP by leukocytes in vitro was not inhibited by IM (10 μg/ml). In our previous report, it was ascertained that the rectal temperature of normal rabbits remained unchanged after intravenous injection of IM. Thses results suggest that indomethacin may inhibit only the pyretic processes in the central nervous system.

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Cells from pregnant rabbit uterine cervix in primary cultures produced specific collagenase and gelatinolytic metallproteinase, both in latent forms. The two enzymes were separated by CM-52 cellulose chromatography. Dehydroepiandrosterone 3-sulphate (DHAS) stimulated the production of the latent collagenase by the cells in a dose-dependent manner and the maximal effect, which was about 2-fold of control cultures, was observed when 1×10^-6 M DHAS was added to the medium containing 10% (v/v) foetal calf serum (FCS). DHAS also stimulated the production of the gelatinolytic metalloproteinase. The significant stimulative effects were also confirmed when the cells were incubated with 1×10^-7 M DHAS in the medium containing 9% (v/v) dextran-coated charcoal treated FCS and 1% (v/v) FCS. The uptake of [³H] DHAS by the cells from pregnant rabbits was 5-10-fold greater than that from nonpregnant rabbits. When confluent cultures were incubated with 6.5×10^-8 M [³H] DHAS for 2 d, 3.4% and 0.03% of total radioactivity added were accumulated as [³H] oestradiol-17β([³H]E₂) in the medium and cell layer, respectively. Nevertheless, the addition of 1×10^-9 M and 1×10^-11 M E₂ or dehydroepiandrosterone (DHA) to the confluent cultures caused no significant effect on the collagenase production. These results strongly suggest that the stimulative effect of DHAS on the production of collagenase and gelatinolytic metalloproteinase by the rabbit uterine cervical cells was due to unchanged DHAS and not due to E₂ or DHA converted from DHAS.

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A new experimental method using a hamster cheek pouch in vivo for studying absorption processes across the keratinized oral mucous membrane was developed and some characteristics of the oral-mucosal absorption were clarified. A possitive correlation between the absorption rate and the lipophilicity was observed in 18 aromatic compounds examined. The absorption of ionizable compounds was poor in the ionized form. These results suggest that the absorption from the keratinized hamster cheek pouch is due to a passive diffusion mechanism and obeys pH-partition hypothesis. The systemic transfer of salicylic acid after intra-cheek-pouch administration could be approximated by the first-order absorption model including a lag time process and the plasma levels found were consistent with this model.

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Dimethadione (DMO)/trimerhadione (TMO) ratios in serum after oral administration of TMO were investigated in 15 normal subjects and in 20 patients with cirrhosis and esophageal varices. Severe impairment of liver function was associated with a decrease in total cholesterol, total protein and plasma albumin, or an increase in total bilirubin, serum glutamic oxaloacetic transaminsase, serum glutamic pyruvic transaminase, serum γ-glutamyl transpeptidase and indocyanine green retention rate (ICG R₁₅). Serum concentration ratios of DMO to TMO at 2 or 4 h after oral administration of TMO in patients were significantly decreased by 67 or 66%, respectively, compared to normal subjects. DMO/TMO ratios at 2 or 4 h following oral administration of TMO were well correlated with the liver function parameters (plasma albumin r=0.758 at 2 h, r=0.776 at 4 h ; total protein r=0.613 at 2 h, r=0.619 at 4 h ; ICG R ₁₅ r=-0.683 at 2 h, r=-0.746 at 4 h, in patients only ; cholinesterase r=0.873 at 2 h, r=0.908 at 4 h) as well as with pharmacokinetic parameters (total body clearance r=0.794 at 2 h, r=0.786 at 4 h) in both the normal subjects and the patients. It suggests that the DMO/TMO ratio obtained in a single blood sample collected after oral administration of TMO might provide a useful measure for function hepatic reserve.

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Disposition of 1-benzenesulfonyl-5, 5-diphenylhydantoin (II) having a potent anti-inflammatory activity was compared with that of 5, 5-diphenylhydantoin (I), an antiepileptic drug, in order to elucidate whether the pharmacodynamic difference between them can be explained by their physicochemical and pharmacokinetic properties. After oral administration of I-¹⁴C to rats, radioactivity was distributed in all tissues including the brain, whereas after II-¹⁴C administration, the concentrations of radioactivity in most tissues were lower than those in plasma. The results were consistent with the finding obtained by whole-body autoradiography which revealed that after oral administration of II-¹⁴C to rats, radioactivity was not transferred into brain but was significantly transferred into inflamed tissues. Brain/plasma concentration ratio of I was about 1.3, whereas that of II was about 0.05. Plasma protein binding of I having pK_a value of 8.30 was about 88%, whereas that of II having pK_a value of 4.89 was about 99%. The changes in physicochemical properties due to introduction of a benzenesulfonyl group into the hydantoin ring may be responsible for the difference in the disposition between I and II. When II was cerebroventricularly administered to mice, it showed a potent anticonvulsant activity against maximal electroshock seizure, the activity being comparable to that for I. This indicates that the earlier failure to demonstrate the activity of II in a routine screening test for antiepileptic drugs was due to the inability of II to penetrate the bloodbrain barrier and to achieve effective concentration in the brain. II was found to inhibit the biosynthesis of prostaglandin. These findings along with the physicochemical properties suggest that although II does not fall structurally under any category of anti-inflammatory drugs the mechanism of action may be similar to that for non-steroidal acidic anti-inflammatory drugs.

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5-[(2-Aminoacetamide) methyl]-1-[p-chloro-2-(o-chlorobenzoyl) phenyl]-N, N-dimethyl-1 H-s-triazole-3-carboxamide hydrochloride dihydrate (450191-S) is a newly synthesized sleep inducer, which itself has negligible affinities for benzodiazepine receptors. However, several active metabolites have been found in rat plasma. In this paper, the mechanisms and contribution of the activation of 450191-S in rat small intestine were investigated. When 450191-S was incubated with rat everted small intestine, desglycylated 450191-S (191DG) was released in the medium and subsequently converted to 8-chloro-6-(2-chlorophenyl)-N, N-dimethyl-4 H-1, 2, 4-triazolo [1, 5-a][1, 4] benzodiazepine-2-carboxamide (M-1). The results obtained using synthetic 191DG indicated that the conversion of 191DG to M-1 was spontaneous and very rapid, with a half-life of 9 min in pH 7.4 buffer. After incubation, the intestinal tissue contained a small amount of unchanged 450191-S but large amounts of 191DG and/or M-1. Next, metabolites in the mesenteric blood were determined following instillation of ¹⁴C-450191-S into a segment of rat ileum and it was found that almost all of the radioactivity in the blood was accounted for by 191DG and/or M-1. In conclusion, 450191-S is metabolized by intestinal aminopeptidases to 191DG, which is spontaneously converted to M-1, an active metabolite, and the activation is completed by a single passage through the intestinal wall.

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The optimal absorption site of cimetidine was assessed in rats. The ileac pH value (measured by a pH meter with a micro pH combination electrode) was slightly higher than that in other intestinal sites, and the absorption rate constant (k_a) following the administration of cimetidine into the ligated ileac loop was larger than that in the ligated duodenal and jejunal loops. It is suggested that the ileum is the optimal absorption site of cimetidine. On administration of cimetidine into the ligated and unligated intestines, the k_a values of either the duodenum or the ileum were found to be almost the same between the ligated and unligated cases. However, the k_a value of the jejunum in the unligated case was slightly larger than that in the ligated case. Thus, it is suggested that cimetidine is completely absorbed in the duodenum and ileum during its passage through these intestinal sites, but at the jejunum an unabsorbed fraction of cimetidine passes to the ileum, where it is absorbed completely. Based on these results, a pharmacokinetic model for the absorption of cimetidine following oral administration was designed, in which gastric, duodenal, jejunal, and ileac compartments were included separately but enterohepatic circulation was not included, because the biliary excretion of cimetidine following intravenous and oral administrations were generally lower than 2% of the dose. The value of k₄₁ was ca. 4 times larger than that of k₄₅, and the value of k₄₅ could be approximated to zero in the model.

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It is suggested that cimetidine interacts with the transport system for organic anions and oligopeptides in the rat lateral ventricular choroid plexus. In this study, we studied the transport system of cimetidine in the rat 4th ventricular choroid plexus to examine the heterogeneity in the ability to accumulate cimetidine between the lateral and the 4th ventricular choroid plexus. The similar time course of the accumulation of cimetidine was obtained between both choroid plexuses. Furthermore, the accumulation of cimetidine by the choroid plexus from the 4th ventricle was inhibited by unlabelled cimetidine (1 mM) and benzylpenicillin (1 mM) but not by tetraethyammonium (1 mM). These findings suggested that the rat choroid plexuses from the lateral and the 4th ventricle have similar characteristics in transporting cimetidine.

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