Recent updates in utilizing prodrugs in drug delivery (2013–2015)

ABSTRACT

Introduction: Utilizing the prodrug approach as a method to overcome various pharmaceutical and pharmacokinetic barriers to drug delivery is significantly accelerating and achieving successes. In contrast to the older traditional prodrugs which suffer from decreased bioavailability and a high profile of side effects, due to activation at undesired sites, the targeted prodrug approach utilizes delivery systems to improve delivery for a wide range of therapeutics including anti-cancer, anti-bacterial and anti-inflammatory drugs.

Areas covered: Recent updates in utilization of prodrugs in drug delivery between 2013 and 2015 are discussed. Targeted prodrugs against cancer, solid tumors, microbial infections, inflammation and other diseases using advanced delivery systems such as theranostic approaches, siRNA, DOX immunoconjugate, C 60-ser carrier vector, biotinylated prodrug, human serum albumin (HSA) carrier and others are presented.

Expert opinion: Recent research efforts have been directed at developing targeted prodrugs to replace the classical prodrugs. The use of this approach has accelerated following the emergence of encouraging results from several studies on targeted prodrugs that have highlighted their higher efficiency and improved safety profiles.

Targeted prodrug delivery is now considered more than a chemical modification method. It is an applicable and promising approach and, in the future, better knowledge and wide application of this approach may be attained which may pave the way for more forward-thinking and creative techniques.     

α-Monofluoromethyldopa (MFMD) in combination withl-DOPA

Summary We have investigated the interaction of -monofluoromethyldopa (MFMD) with the effects of i.p. injectedl-DOPA (200 mg·kg^–1) on blood pressure and tissue catecholamines in normal and spontaneously hypertensive rats (SHR). MFMD 10 mg·kg^–1 (i.p.) effectively antagonizes thel-DOPA induced increase in heart dopamine (DA). This action is also seen after 15 or 50 mg·kg^–1. The accumulation of DA in the brain is very much reduced by MFMD 50 mg ·kg^–1 while after 15 or, especially, 10 mg·kg^–1 more DA is formed in the rrain than afterl-DOPA alone, probably due to the peripheral decarboxylase inhibition which presents morel-DOPA to the brain. We conclude that MFMD 10 mg ·kg^–1 gives a relatively selective peripheral inhibition of the decarboxylation ofl-DOPA and this dose combination was accordingly found to result in a reduction of blood pressure in conscious animals. This hypotensive response tol-DOPA was attenuated after MFMD 15 mg·kg^–1 and was absent after MFMD 50 mg·kg^–1. Interestingly, the hypotensive effect ofl-DOPA after MFMD 10 or 15 mg·kg^–1 was more pronounced in SHR.     

Evaluation of sigma (σ) receptors in the antidepressant-like effects of ketamine in vitro and in vivo

Ketamine is an NMDA antagonist and dissociative anesthetic that has been shown to display rapid acting and prolonged antidepressant activity in small-scale human clinical trials. Ketamine also binds to σ receptors, which are believed to be protein targets for a potential new class of antidepressant medications. The purpose of this study was to determine the involvement of σ receptors in the antidepressant-like actions of ketamine. Competition binding assays were performed to assess the affinity of ketamine for σ(1) and σ(2) receptors. The antidepressant-like effects of ketamine were assessed in vitro using a neurite outgrowth model and PC12 cells, and in vivo using the forced swim test. The σ receptor antagonists, NE-100 and BD1047, were evaluated in conjunction with ketamine in these assays to determine the involvement of σ receptors in the antidepressant-like effects of ketamine. Ketamine bound to both σ(1) and σ(2) receptors with μM affinities. Additionally, ketamine potentiated NGF-induced neurite outgrowth in PC12 cells and this effect was attenuated in the presence of NE-100. Ketamine also displayed antidepressant-like effects in the forced swim test; however, these effects were not attenuated by pretreatment with NE-100 or BD1047. Taken together, these data suggest that σ receptor-mediated neuronal remodeling may contribute to the antidepressant effects of ketamine.     

Dextranomer in stabilized sodium hyaluronate (Solesta®): in adults with faecal incontinence

Dextranomer in stabilized sodium hyaluronate, hereafter referred to as dextranomer/hyaluronic acid, is a biocompatible bulking agent administered by submucosal injection. It is hypothesized to expand the submucosal layer of the proximal anal canal, thereby augmenting bowel control. Treatment with dextranomer/hyaluronic acid was associated with symptomatic improvements in adult patients with faecal incontinence participating in a randomized, double-blind, sham-controlled, multinational study and a noncomparative, multinational study. In the double-blind study, patients in the dextranomer/hyaluronic acid group met the primary efficacy objective in that a significantly higher proportion of patients responded to treatment (≥50% reduction from baseline in the number of incontinence episodes) at the 6-month post-treatment timepoint than in the sham group (two of three primary response criteria), with the durability of the treatment response (≥25% reduction from baseline in the number of incontinence episodes) confirmed at the 12-month post-treatment timepoint (third primary response criterion). For the most part, dextranomer/hyaluronic acid did not significantly differ from the sham treatment in terms of quality of life and various other symptomatic endpoints at 6 months post-treatment in the double-blind study, although there were significant improvements from baseline in various parameters, such as the mean number of incontinence-free days, the median number of incontinence episodes and mean Faecal Incontinence Quality of Life domain scores, at 12 months post-treatment. In general, dextranomer/hyaluronic acid was well tolerated for up to 18 months post-treatment, with the majority of treatment-related adverse events considered mild or moderate in intensity.     

Effect of 3,6-dimethamidodibenzopyriodonium citrate on Ca~(2 ) in rabbit platelet in vitro

目的：观察Ｉ６５对家兔血小板胞浆游离钙离子（［Ｃａ２＋］ｉ）浓度的影响．方法：用Ｑｕｉｎ２ＡＭ荧光探针在体外测定家兔血小板［Ｃａ２＋］ｉ．结果：ＣａＣｌ２１ｍｍｏｌ·Ｌ－１时，Ｉ６５（１０，２０和３０μｍｏｌ·Ｌ－１）使血小板［Ｃａ２＋］ｉ分别由１４２±２２ｎｍｏｌ·Ｌ－１和１２４±１８ｎｍｏｌ·Ｌ－１减少到１１８±２０，７８±１２，４０±１０ｎｍｏｌ·Ｌ－１和１０８±１５，７７±１４，３７±１４ｎｍｏｌ·Ｌ－１．用依他酸２ｍｍｏｌ·Ｌ－１络合胞外Ｃａ２＋，Ｉ６５胞内贮存Ｃａ２＋释放从５２±１１ｎｍｏｌ·Ｌ－１减少至３４±９，１９±６和１１±５ｎｍｏｌ·Ｌ－１．另外，Ｉ６５也使胞外Ｃａ２＋跨膜内流从９１±１３ｎｍｏｌ·Ｌ－１分别降至８４±１５，５８±１５和２８±１９ｎｍｏｌ·Ｌ－１．结论：Ｉ６５不仅明显抑制家兔血小板胞外Ｃａ２＋跨膜内流而且抑制胞内贮存Ｃａ２＋释放．     

α(1)-Adrenoceptors in the urinary tract

α(1)-Adrenoceptors have been identified and characterized extensively by functional, radioligand-binding, and molecular biological techniques. Molecular clones have been isolated for three α(1)-subtypes (α(1a), α(1b), and α(1d)), and these subtypes are also functionally characterized. α(1)-Adrenoceptors are present in the prostate, urethra, bladder (urothelium, smooth muscle, and afferent nerves), ureter, vas deferens, peripheral ganglia, nerve terminals, vascular tissues, and central nervous system (CNS), and they could all potentially influence overall urinary function and contribute to both the therapeutic and adverse effects of α(1)-adrenoceptor antagonists in patients with benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). This review aimed to discuss the relevant physiological and pharmacological roles and molecular biology of α(1)-adrenoceptor subtypes in the prostate, urethra, bladder, ureter, and CNS.     

The Metabolites of Oxprenolol (Trasicor®) in man

Abstract

1. Two volunteers given a single oral dose of [³H]oxprenolol, excreted 70% and 95% of the radioactivity in the urine in 48 h. 78% and 71% of the urinary radioactivity is attributed to metabolites more polar than oxprenolol.

2. Metabolites, identified by mass spectrometry and isotope dilution analysis were as follows: I. the glucuronide of unchanged oxprenolol, II. a conjugate of a derivative of oxprenolol hydroxylated in the aromatic ring, III. unchanged oxprenolol, IV. the hydroxycarboxylic acid derived from oxprenolol by oxidative deamination, V. a carboxylic acid with the carboxyl group in the position of the former carbinol, VI. the monoallyl ether of catechol.     

Increase of δ-Aminolevulinic Acid Dehydratase (ALAD) in rat erythrocytes in lead poisoning

The well known fact that the activity of δ-aminolevulinic acid dehydratase (ALAD: EC 4.2.1.24) is reduced in red cells of animals with lead poisoning was found to be upset, by using a modified method of Gibson's original procedure, for determination of activated ALAD activity. The modified method involves addition of 0.2 mM Zn²⁺ and then preheating the enzyme solution at 60° C for 5 min before following Gibson's original procedure. With this methodological modification, the ALAD activity of erythrocytes of rats poisoned with lead was found increased. Furthermore, the enzyme was purified from the peripheral blood of lead-poisoned rats. ALAD protein in peripheral blood was also determined by single radial immuno diffusion using rabbit anti-serum raised against rat liver ALAD. As the result, the ALAD activity obtained from the modified method was found to be directly proportional to the absolute amount of enzyme proteins determined both by chemically and immunochemically. The modified method for measuring true ALAD content in blood cells in lead poisoning is more reliable than previous ones.     

Absorption characteristic of paeoniflorin-6′-O-benzene sulfonate (CP-25) in in situ single-pass intestinal perfusion in rats

1.?Paeoniflorin-6′-O-benzene sulfonate (CP-25) was synthesized to improve the poor oral absorption of paeoniflorin (Pae).

2.?This study was performed to investigate the absorptive behavior and mechanism of CP-25 in in situ single-pass intestinal perfusion in rats, using Pae as a control.

3.?The results showed that intestinal absorption of CP-25 was neither segmental nor sex dependent. However, the main segment of intestine that absorbed Pae was the duodenum. Furthermore, passive transport was confirmed to be the main absorption pattern of CP-25. More importantly, the absorption of CP-25 was much higher than Pae in the small intestine.

4.?Among the ABC transporter inhibitors, the absorption rate of Pae increased in the presence of P-gp inhibitors verapamil and GF120918, which indicated that Pae was a substrate of P-glycoprotein (P-gp), however, such was not observed in the presence of breast cancer resistance protein and multidrug resistance-associated protein 2. Finally, the ABC transporter inhibitors did not have any significant impact on CP-25 as demonstrated in the parallel studies.

5.?CP-25 could improve the poor absorption of Pae, which may be attributed to both the lipid solubility enhancement and its resistance to P-gp-mediated efflux.     

Tyrosine kinases participate in α_(1A)-adrenoceptor-mediated vasoconstriction in perfused rat hindlimb

目的：研究酪氨酸激酶是否参与α１Ａ肾上腺素受体引起血管平滑肌收缩的信号传导．方法：灌流大鼠后肢血管床标本，观察酪氨酸激酶抑制剂对去甲肾上腺素（ＮＥ）引起收缩反应的影响．结果：酪氨酸激酶抑制剂ｔｙｒｐｈｏｓｔｉｎ和ｇｅｎｉｓｔｅｉｎ均显著抑制ＮＥ引起的收缩反应，但对ＫＣｌ引起的收缩反应无影响；酪氨酸磷酸酶抑制剂Ｎａ３ＶＯ４显著加强ＮＥ引起的收缩反应；ｔｙｒｐｈｏｓｔｉｎ和ｇｅｎｉｓｔｅｉｎ对蛋白激酶Ｃ激动剂ｐｈｏｒｂｏｌ１２ｍｙｒｉｓｔａｔｅ１３ａｃｅｔａｔｅ引起的收缩反应均无影响，但均抑制Ｇ蛋白激动剂ＮａＦ引起的收缩反应．结论：Ｔｙｒｐｈｏｓｔｉｎ和ｇｅｎｉｓｔｅｉｎ敏感的酪氨酸激酶参与α１Ａ肾上腺素受体介导的大鼠后肢血管床收缩反应     

Amphotericin-B-loaded polymersomes formulation (PAMBO) based on (PEG)₃-PLA copolymers: an in vivo evaluation in a murine model

This paper deals with in vivo evaluation of a new amphotericin-B-loaded polymersomes (PAMBO) formulation in terms of pharmacokinetics, toxicity, tissue distribution profile, and its efficacy in a murine model of disseminated candidiasis. Pharmacokinetic and tissue distribution studies of the PAMBO showed sustained levels of the drug in plasma as well as in target organs which harbor fungal and leishmanial infection. PAMBO was found to be much less toxic than Fungizone. It was observed that 700% increment in the dose is tolerated without observable toxicity which is supported by survival, biochemical, and histopathological results. PAMBO showed a significant improvement in the survival rate of immunosuppressed mice infected with Candida albicans as compared to control. It also showed better dose to dose (1 mg/kg) efficacy as compared to Fungizone and a significant improvement in the life expectancy at 3 and 5 mg/kg dose levels in the animals. Colony forming unit (CFU) counts in the target organs revealed significant reduction in Candida burden with PAMBO treatment. Kidney, spleen, and lung were cleared of infection, although liver was carrying a very low level of infection. Overall, PAMBO formulation is found to be more efficacious and less toxic in a fungal mice model.     

Learning impairment by Δ(9)-tetrahydrocannabinol in adolescence is attributable to deficits in chunking

Cannabis is the most popular illicit drug used by adolescents. Yet, there are only a few studies that have examined the effects of cannabis use on learning and memory during this sensitive and important neurodevelopmental stage. Male adolescent Sprague-Dawley rats were treated with Δ(9)-tetrahydrocannabinol (THC, 6 mg/kg) daily for 27 days and concurrently trained in a spatial learning and memory task. The chronic effects of cannabis use were specifically examined by assessing animal behaviour during the 'postacute' period (17 h after drug exposure), when minimal acute drug burden is expected to be present. The postacute period is a good model for cannabis use patterns in human adolescents. In addition, we investigated whether the hierarchical organization of working memory (chunking) was impaired by THC-treatment. We show that THC exposure impairs adolescent learning when tested in the postacute period, and that THC impairs the ability of animals to use a chunking strategy.     

Potassium conservation with amiloride/hydrochlorothiazide (‘Moduret’) in thiazide-induced hypokalaemia in hypertension

Summary

A double-blind study was carried out in 24 hypertensive patients with thiazide-induced hypokalaemia (serum potassium <3.2 mmol/l) to compare the effects of treatment with an amiloride/hydrochlorothiazide combination or hydrochlorothiazide alone. The study was divided into three phases: (i) potassium repletion (Weeks 0 to 4) with oral potassium chloride (40 mmol/day), (ii) stabilization (Weeks 4 to 6) of normokalaemia, and (Hi) active drug treatment (Weeks 6 to 14), patients being allocated at random to receive one or other of the two treatments. Dosage was 2 tablets per day of the 5?mg amiloride plus 50?mg hydrochlorothiazide combination or of 50?mg hydrochlorothiazide alone. The results showed that blood pressure control was comparable in both treatment groups but hydrochlorothiazide alone caused a statistically significant reduction in serum potassium levels compared to the drug combination. Apart from 1 patient who developed hypokalaemia on hydrochlorothiazide alone, no other side-effects of treatment were reported.     

Biotransformation and pharmacokinetics of sulfinpyrazone (Anturan®) in man

Summary The absorption, biotransformation and elimination of sulfinpyrazone, 1,2-diphenyl-3,5-dioxo-4-(2-phenylsufinylethyl)-pyrazolidine, have been studied by administration of single 200 mg oral doses of a¹⁴C-labelled preparation to two male volunteers. Absorption from the gastro-intestinal tract was rapid and complete and the plasma concentration of unchanged drug reached maximum values of 22.67 and 13.04 µg/ml, respectively, after 1 – 2 hours. The elimination half-life in the two subjects, calculated from the decline between 3 and 8 hours, was 2.7 and 2.2 hours. The integrated concentration of unchanged sulfinpyrazone in plasma, estimated from the area under the concentration curves (AUC), was almost as high as that of total¹⁴C-substances, so the proportion of metabolized drug in plasma was low. In no case did the AUC of the three specifically determined metabolites, i.e. the sulphone G 31 442, the para-hydroxy-compound G 32 642 and the 4-hydroxy-compound GP 52 097, exceed 4% of the sulfinpyrazone value. More than 95% of whole blood radioactivity was confined to plasma. The oral dose was rapidly and completely excreted, since within 4 days more than 95% was recovered, 85% from urine and 10% from faeces. A large proportion of the dose was excreted as unchanged drug in the two volunteers: 51 and 54% of total urinary radioactivity was present as sulfinpyrazone; 8.2 and 8.8% was present as para-hydroxy-metabolite, 2.7 and 3.0% as sulphone-metabolite, and 0.6 and 0.8% as 4-hydroxy-metabolite. About 30% of urinary radioactivity consisted of highly polar metabolites. Spectroscopy of them showed that they were the C--glucuronides of sulfinpyrazone (28%) and the corresponding sulfone (2%). In these metabolites the C(4) of the pyrazolidine ring was directly attached to glucuronic acid, and thus they represent a new type of biosynthetic conjugate.     

Poly(ε-Caprolactone) Nanocapsules in Carteolol Ophthalmic Delivery

In order to increase the ocular absorption of carteolol, this antiglaucomatous drug was incorporated into either nanoparticles (NP) or nanocapsules (NC). The polymer used was poly(-caprolactone) (PCL). The dosage forms were tested on intraocular hypertensive-induced rabbits. Results are presented as the chronological variations of the intraocular pressure (IOP) in comparison with the commercial aqueous solution (Carteol eye drops). The therapeutic results (decrease in IOP) were much more pronounced with carteolol incorporated into the colloidal carriers than with the commercial eye drops. Further, NC displayed a better effect than NP because the drug was entrapped in the oily core of the carrier, thus more readily available to the eye. The incorporation of the drug into nanocapsules produced a decline in the cardiovascular side effects in comparison with aqueous eye drops, thus showing that the undesired noncorneal absorption was reduced. In conclusion, colloidal suspension made of poly(-caprolactone) could offer a good opportunity for ophthalmic delivery of drugs.     

Biotransformation and pharmacokinetics of acenocoumarol (Sintrom®) in man

Summary The absorption, biotransformation and elimination of the anticoagulant acenocoumarol, 3-[- (4-nitrophenyl)--acetylethyl]-4-hydroxycoumarin, have been studied by oral administration of 12 mg of a¹⁴C-labelled preparation to two male volunteers. Absorption from the gastro-intestinal tract was rapid and the plasma concentration of unchanged drug reached a maximum of 169 and 412 ng/ml, respectively, after 3 hours. The elimination half-life in the two subjects, calculated from the decline between 6 and 24 h, was 8.7 and 8.2 hours. A constant proportion of 98.7% of the drug was bound in vitro to serum proteins over a concentration range of 0.021–8.34 µg/ml, with little interindividual variation. The major portion of the binding was to human serum albumin (97.5%) at two classes of binding sites: association constant K₁=1.04×10⁵ l/mole (n₁=1) and K₂=5.55×10³ l/mole (n₂=4). In addition to unchanged acenocoumarol, four metabolites were determined in plasma by isotope dilution techniques: the amino-, acetamido-, alcohol₁- and alcohol₂-metabolites. Of them, the amino-metabolite showed the highest concentration, namely 278 ng/ml, after 6 h in Subject A, and 163 ng/ml after 10 hours in Subject B. Judged from the integrated concentrations, the compounds analyzed accounted for 76 and 89%, respectively, of the total radioactivity in plasma. All the metabolites detected in plasma showed anticoagulant activity when tested in mice. The quantities of the metabolites excreted in urine from 0–120 hours were (Subject A/Subject B): acenocoumarol 0.3/0.2%, amino-metabolite 12.3/7.7%, acetamido-metabolite 19.0/11.1%, alcohol₁-metabolite 4.6/9.0%, alcohol₂-metabolite 1.7/4.4%, 6-hydroxy-metabolite 6.9/18.3% and 7-hydroxy-metabolite 14.0/22.2%.     

Toxicology and carcinogenesis studies of transplacental AZT (Cas No. 30516-87-1) in Swiss (CD-1®) mice (in utero studies)

3'-Azido-3'-deoxythymidine (AZT) is the most widely used and evaluated chemotherapeutic agent for the treatment of persons with acquired immune deficiency syndrome (AIDS) and persons seropositive for human immunodeficiency virus (HIV). The study in this report was conducted to obtain information on AZT transplacental carcinogenicity at doses that were lower than those used in previous NCI studies and analogous to therapeutic doses. Male and female Swiss (CD-1(R)) mice were exposed to AZT (greater than 99% pure) during all of gestation. Genetic toxicology studies were conducted in mouse peripheral blood erythrocytes. Groups of 22, 28, 34, or 46 female mice (F(0) generation) were administered AZT in 0.5% methylcellulose by gavage at doses of 50, 100, 200, or 300 mg AZT/kg body weight 7 days per week for 29 to 39 days (day of delivery). A vehicle control group of 22 female mice received methylcellulose alone. Each female group was divided into two groups with dosing started 1 week apart in order to facilitate cohabitation, mating, and delivery. Groups of six, six, seven, nine, or twelve undosed male mice were cohabited with the vehicle control and 50, 100, 200, and 300 mg/kg dosed females, respectively, on study days 9 to 13 and then discarded. Pups (F(1) generation) were culled (0, 50, and 100 mg/kg groups) to yield a maximum of five pups/sex per litter on postnatal day 4; no more than four pups/sex per litter were used in the study. On postnatal day 25, all surviving 200 and 300 mg/kg pups were placed on study. After culling and randomization to cage groups, the 0, 50, 100, 200, and 300 mg/kg groups consisted of 50, 50, 50, 37, and 32 male pups and 50, 50, 50, 40, and 42 female pups, respectively. Decreased litter size and fertility rates were observed in the 200 and 300 mg/kg F0 dams. Survival of all exposed groups of F(1) mice was similar to that of the vehicle controls. Mean body weights of 200 mg/kg males were generally less than those of the vehicle controls after week 29. Mean body weights of 300 mg/kg males were less during the first year of the study, but these mice recovered and body weights were generally similar to those of the vehicle controls at the end of the study. The incidences of alveolar/bronchiolar carcinoma and of adenoma or carcinoma (combined) in 200 and 300 mg/kg males were significantly greater than those in the vehicle controls. The incidences of histiocytic cellular infiltration of the lung in 200 and 300 mg/kg males were significantly increased. GENETIC TOXICOLOGY: The NTP conducted a number of studies of the genetic toxicity of AZT, independent of this transplacental carcinogenicity study. In these genetic toxicity studies, AZT (50, 75, 100, or 150 mg/kg) administered to pregnant Swiss (CD-1(R)) dams, beginning prior to conception and continuing throughout gestation and lactation, induced high levels of micronucleated polychromatic erythrocytes (PCEs) in pups sampled on postnatal days 1 and 4. Direct gavage treatment of these transplacentally and lactationally exposed pups, beginning on postnatal day 4, resulted in further increases in the frequencies of micronucleated PCEs on postnatal days 8 and 21. The percentage of PCEs among erythrocytes in pups was significantly elevated over normal adult levels, indicating a high rate of erythropoiesis in neonatal mice. The percentage of PCEs was decreased in all pups exposed to AZT, consistent with treatment-related bone marrow toxicity. CONCLUSIONS: Under the conditions of this study, there was clear evidence of carcinogenic activity in F(1) male mice exposed transplacentally to AZT based on increased incidences of alveolar/bronchiolar neoplasms. There was no evidence of carcinogenic activity in F(1) female mice exposed transplacentally to AZT at 50, 100, 200, or 300 mg/kg. Reproductive toxicity in the form of decreased litter size and fertility rates was observed in dams in the 200 and 300 mg AZT/kg dose groups.     

Correlation of the intrinsic clearance of donepezil (Aricept®) between in vivo and in vitro studies in rat,dog and human

1. Donepezil hydrochloride (Aricept®) is used for the treatment of Alzheimer's disease. Here the correlation of the intrinsic clearance (Cl_int) of donepezil between the in vivo and in vitro states was studied in rat, dog and human. 2. In an experiment with ¹⁴C-donepezil and human microsomes the routes of metabolism were identified as N-dealkylation and O-demethylation, and no unknown metabolites were detected. 3. The Cl_int of donepezil in the male rat, female rat, dog and human liver microsomes were 33.7, 13.4, 37.0 and 6.35 μl/min/mg microsomal protein respectively, and sex difference in rat and interspecies difference in the estimated Cl_int were found. 4. After a single intravenous administration to the male rat, female rat and dog, total plasma clearance (Cl^P_total) was 78.6, 29.5 and 88.3 ml/min/kg respectively, and a sex difference was observed in rat. 5. After a single oral administration to the male rat, dog and healthy volunteer, Cl^P_total/F was 140, 105 and 2.35 ml/min/kg respectively, and remarkable differences were observed between animals and man. 6. The contribution of renal clearance to blood clearance (Cl_r) was low in all species. The predicted in vitro hepatic clearance (Cl_h-pre) was in the rank order: male rat (15.91 ml/min/kg) &gt; dog (7.96) &gt; female rat (7.67) &gt; human (1.04). Although Cl_h-pre was underestimated, Cl_h-pre was significantly correlated with that of ClBtotal in the different animal species and in man, indicating that the in vitro-in vivo ranking order was conserved.