Suppression of tumor necrosis factor-alpha production by interleukin-10 is enhanced by cAMP-elevating agents

The pro-inflammatory peptide tumor necrosis factor-alpha (TNF) stimulates production of the anti-inflammatory cytokine-interleukin-10 by monocytes which in turn inhibits the synthesis of TNF. This inhibitory effect of interleukin-10 may contribute to the balance of pro- and anti-inflammatory cytokines in several diseases, e.g., chronic inflammatory bowel disease. In the present study we addressed the question whether interleukin-10 in combination with other TNF-suppressing agents leads to enhanced suppression of TNF synthesis. We investigated the inhibitory potency of interleukin-10 in combination with rolipram, a specific type IV phosphodiesterase inhibitor, or with cicaprost, a stable prostacyclin analogue in lipopolysaccharide-stimulated human peripheral blood mononuclear cells. Peripheral blood mononuclear cells were stimulated with 10 ng/ml lipopolysaccharide in the absence or presence of interleukin-10 or one of the cAMP-elevating agents. First, we confirmed the TNF-suppressing effect of interleukin-10, rolipram and cicaprost alone and determined the IC50 for these substances. Second, for the combination of interleukin-10 with one of the cAMP-elevating substances we were able to demonstrate enhanced TNF inhibition. Of these, the combination of interleukin-10 and rolipram revealed an additive effect. The maximal TNF synthesis of 5.5 +/- 1.1 ng/ml after lipopolysaccharide stimulation alone was inhibited by 0.1 ng/ml interleukin-10 to 2.7 +/- 0.6 ng/ml TNF and by 100 nM rolipram to 3.1 +/- 0.6 ng/ml TNF. Both substances combined suppressed TNF synthesis to 1.5 +/- 0.3 ng/ml. After stimulation with Staphylococcus epidermidis we could demonstrate a more pronounced inhibition of TNF synthesis by interleukin-10 compared to rolipram which was more effective after stimulation with lipopolysaccharide. Finally, the additive inhibitory effect of interleukin-10 and rolipram could be confirmed on the level of TNF mRNA. The results obtained in the present investigation could form a prerequisite to study the combination of interleukin-10 and cAMP-elevating agents in in vivo models of acute or chronic inflammatory diseases.

Pharmacokinetic study of aniracetam in elderly patients with cerebrovascular disease

The clinical pharmacokinetics of the cognitive enhancer, aniracetam (200 mg), was studied in elderly patients with cerebrovascular disease (CVD) and compared with those of young healthy volunteers. Six female hospitalized patients (mean age 84.5 years) were used in this study. The serum level of anisic acid and p-methoxyhippuric acid, major metabolites of aniracetam, reached a peak at 2 h after oral administration, and returned to basal level by 6 h. Mean creatinine clearance was 20-30 ml/min. The t1/2 of metabolites was increased by 4- to 7-fold in the elderly patients compared with young volunteers. This study showed that tmax, t1/2, and AUC were enlarged in the elderly; however, no clinical side effects were observed.

Major metabolic pathway for N-methyl-2-pyrrolidone in humans

The aim was to study the metabolic pathway for N-methyl-2-pyrrolidone (NMP) in humans. Three healthy male volunteers were administered 100 mg NMP orally. All urine was collected during nine consecutive days. The identification and quantification of the metabolites were performed by gas chromatography/mass spectrometry (GC/MS). NMP, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP), N-methylsuccinimide (MSI), and 2-hydroxy-N-methylsuccinimide (2-HMSI) were found in urine. The mean excreted fractions for NMP, 5-HNMP, MSI, and 2-HMSI were 0.8%, 44%, 0.4%, and 20%, respectively. There was no conjugation with glucoronic acid or sulfate or either 5-HNMP or 2-HMSI. One-third of the orally dosed NMP was not recovered in urine as either NMP, 5-HNMP, MSI, or 2-HMSI. The half-lives for 5-HNMP, MSI, and 2-HMSI in urine were approximately 4, 8, and 17 hr, respectively.

[Localization of cAMP-selective phosphodiesterase in the mammalian eye by (3H)-rolipram]

It has been shown that inhibition of phosphodiesterase (PDE) or an increase in intracellular cyclic adenosine monophosphate (cAMP) can lower the intraocular pressure in mammalian eyes. The PDE inhibitor rolipram binds with high affinity to a cAMP-dependent PDE. In the following study, receptors for rolipram in the mammalian eye are determined by autoradiography. About 1050 histological sections of rabbit (albino and pigmented), rat, monkey (baboon and marmoset) and human eyes were examined concerning rolipram-binding sites in different structures. The highest specific binding of rolipram to the ciliary body epithelium was seen in human, rabbit and baboon eyes. Marmoset eyes showed the highest specific binding in the ciliary body muscle, rat eyes in the retina. Specific binding was consistently high in the ciliary body epithelium and therefore at the site of aqueous humor formation. Because of these results and the known mode of action of rolipram, one can assume a close connection between rolipram-binding sites and the regulation of intraocular pressure.

Nefiracetam hydroxylation by rat liver microsomes and expressed human cytochrome P450s

1. The metabolism of nefiracetam, a novel cognition-enhancer, by rat liver microsomes has been studied. 2. Formation of 5-hydroxy (5-OH-NEF) and hydroxymethyl (HM-NEF) derivatives was the principal pathway of NEF oxidation in male rats, and followed Michaelis-Menten kinetics with Km values of 2.9 and 3.3 mM, and Vmax values of 7.8 and 4.5 nmol/min/mg protein, respectively. 3. Enzymes catalysing the formation of these two major metabolites were examined. 5-OH-NEF formation was inhibited by antibody to rat CYP3A2 by 60%, and antibodies to CYP2B1, CYP2C11 and CYP2E1 also showed 15-25% inhibition of the formation of 5-OH-NEF. The formation of HM-NEF was inhibited by antibodies to CYP2C11 and CYP2B1 by 80% and 35%, respectively. These findings indicate that CYP3A plays a major role in the formation of 5-OH-NEF, and CYP2B, CYP2C11 and CYP2E1 are also involved to some extent in the 5-hydroxylation, and that CYP2C11 is mainly responsible for HM-NEF formation, and CYP2B is also involved in that catalysis in male rats. The results from the studies of the effects of various chemical inducers, of selective substrates or inhibitors of P450s on the formation of these metabolites also supported these latter findings. 4. NEF metabolism in microsomes prepared from B-lymphoblastoid cells expressing human cytochrome P450s showed that 5-OH-NEF formation by CYP3A4 is the principal metabolic pathway in humans.

[The kinetics of the excretion of a choline-containing polymer from the body of rats and its effect on the activity of intestinal enzymes]

It was shown that the studied choline-containing polymer is practically not absorbed in the gastrointestinal tract. It is eliminated mainly on the first day. It causes an inhibitory effect on disaccharidases, does not affect animal growth, and has no negative effect on food uptake.

In vitro metabolism of nefiracetam by liver microsomes from rats, dogs and monkeys

The in vitro metabolism of nefiracetam (CAS 77191-36-7, N-(2,6-dimethylphenyl)-2-(2-oxo-1-pyrrolidinyl) acetamide, NEF, DM-9384), a novel cognition enhancer, has been investigated using liver microsomes from rats, dogs and monkeys. Microsomal metabolism of NEF showed qualitatively a similar profile in three species tested. Six metabolites were generated from incubation of NEF with liver microsomes. Their structures were identified using a thermospray LC/MS/MS (liquid chromatography/tandem mass spectrometry) method, as regioisomers of monhydroxylated derivatives of NEF: the 3-hydroxy (3-OH-NEF); 4-hydroxy (4-OH-NEF); 5-hydroxy (5-OH-NEF); 3'-hydroxy (3'-OH-NEF); 4'-hydroxy (4'-OH-NEF); hydroxymethyl (HM-NEF) metabolites. The heat lability, NADPH requirement and inhibition by prototype cytochrome P450 inhibitors (proadifen and metyrapone) implies that NEF oxidations are catalyzed by cytochromes P450. The major metabolic route was 5-OH-NEF formation in all species, corresponding well with the previous investigations in vivo. Inhibitory effects of alpha-naphthoflavone and quinidine on NEF hydroxylation suggest that several isoforms of cytochromes P450 are involved in the formation of these NEF metabolites.

Discriminative stimulus properties of the stereoisomers of the phosphodiesterase inhibitor rolipram

The discriminative stimulus properties of the specific type IV phosphodiesterase inhibitor, rolipram, and its two stereoisomers were assessed using standard two-lever drug discrimination procedures in which responding on the appropriate lever was reinforced on a FR10 schedule. In three separate drug cues based on training rats to discriminate the racemate (0.2 mg/kg, IP), the (-)-isomer (0.1 mg/kg), or the (+)-isomer (2 mg/kg) from vehicle, all forms substituted for one another, differing only in potency. In keeping with published reports, the (-)-isomer was the more potent form, the (+)-isomer being approximately 10 times less potent. Several phosphodiesterase (PDE) inhibitors were found to substitute for the racemate cue, their potencies in the behavioural measure correlating with their potency in displacing [3H]rolipram from its forebrain binding sites in vivo (r = 0.95), suggesting that the discriminative stimulus depends on an action of the drug upon this site. Because rolipram has been reported to possess antidepressant activity, the ability of the tricyclic antidepressant imipramine to substitute for rolipram was investigated; doses of 10 and 20 mg/kg did not substitute. Amphetamine (0.156-1.25 mg/kg) also was inactive. Lisuride gave rise to drug-appropriate responding in 50% of rats only at a dose of 0.078 mg/kg, which severely disrupted responding. It is concluded that the rolipram discriminative stimulus is dependent on the selective PDE inhibitory activity of the drug, and that it does not constitute a cue based on the antidepressant property of rolipram.

New classes of antimuscarinic agents endowed with selective antispasmodic properties. 1-Arylsulfonyl pyrrolidin-2-ones and 2-thiones, 1-arylsulfonyl piperidin-2-ones and 2-thiones and 1-arylsulfonyl hexahydro-2H-azepin-2-one

A series of 1-arylsulfonylpyrrolidin-2-ones (and 2-thiones), 1-aryl sulfonylpiperidin-2-ones (and 2-thiones) and 1-arylsulfonyl hexahydro-2H-azepin-2-one were synthesized and submitted to a battery of binding assays. The compounds showed little or no affinity for the receptors tested other than muscarinic receptors labelled either with [3H]pirenzepine or with [3H]quinuclidinyl benzilate. When tested in the isolated guinea pig ileum, they antagonized the contractions induced by acetylcholine and behaved as competitive muscarinic antagonists. After parenteral administration in mice, most compounds inhibited carbachol-induced diarrhoea but were less effective in counteracting salivation and lacrimation and showed little or no mydriatic action, thus displaying selectivity at the intestinal level. The reference drugs tested, atropine, butyl scopolamine and cimetropium bromide were far less selective. maximal in vivo activity was obtained by introducing diethylamino or 1-piperidino or 1-hexahydroazepinyl groups in the 4-position of the phenyl ring while the enlargement of a 5- to a 6-membered lactam ring or its conversion into a thiolactam had a less marked effect. The most interesting compounds were further evaluated for their ability to antagonize carbachol-induced colonic hypermotility in the rat and arecoline-induced analgesia in mice. The effect on gastric acid secretion in the rat was also investigated. The overall in vivo data showed that compounds 14, 15, 26 and 27, i.e. those bearing a 1-hexahydroazepinyl group in the 4-position of the phenyl ring, were the most potent and selective compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Aniracetam. An overview of its pharmacodynamic and pharmacokinetic properties, and a review of its therapeutic potential in senile cognitive disorders

Aniracetam is a member of the nootropic class of drugs, which have possible cognition enhancing effects. It appears to positively modulate metabotropic glutamate receptors and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-sensitive glutamate receptors, and may facilitate cholinergic transmission, effects which are possibly related to its mechanism of action. Results from trials in elderly patients with mild to moderate cognitive impairment due to senile dementia of the Alzheimer type suggest that aniracetam may be of benefit, with further trials required to confirm its efficacy profile and to define more precisely those patients most likely to respond to treatment. Aniracetam 1500 mg/day was significantly more effective than placebo in all tests at 4 and 6 months, and in a further 6-month trial was more effective than piracetam 2400 mg/day in 8 of 18 tests. Preliminary evidence in the treatment of patients with cognitive impairment of cerebrovascular origin suggests aniracetam may also be of benefit in this condition. Whilst incidence rates of adverse effects are not yet available, data from trials suggest aniracetam is well tolerated. In particular, aniracetam does not appear to cause increases in liver enzyme levels. The evaluation of drugs for patients with senile cognitive disorders is a difficult area and therapeutic options are currently limited. Preliminary evidence of the potential benefits and good tolerability profile of aniracetam support continued evaluation of its use in patients with mild to moderate senile dementia of the Alzheimer type.

Anti-inflammatory activity of rolipram in a rat ear edema model

In the present study the anti-inflammatory activity of the phosphodiesterase inhibitor rolipram (ZK 62,711, CAS 61413-54-5) was tested in a rat model where edema was induced in the ears of the animals by the epicutaneous application of croton oil in ethanol (5%, by volume). The administration of 0.015, 0.15 and 1.5 mg rolipram per ear dose-dependently inhibited the formation of edema. Concomitantly, the body temperature of the rats was decreased. 4-14% of rolipram was percutaneously absorbed within a 5-h interval. The absorbed proportion, represented by the area under the plasma level-time curve, correlated with the inhibition of edema formation and with the decrease in body temperature.

Biotransformation of the antidepressant D,L-rolipram. II. Metabolite patterns in man, rat, rabbit, rhesus and cynomolgus monkey

1. The metabolism of D,L-rolipram in man was studied by comparison of h.p.l.c. radiochromatograms of plasma and urine obtained at various times following oral and/or s.c. administration to man, rat, rabbit, and rhesus and cynomolgus monkey. 2. Seven metabolites isolated previously from man, rat, and rhesus monkey urine by preparative h.p.l.c. and identified by mass spectrometry and n.m.r. analysis were used for metabolite identification. 3. In plasma, 3-5 metabolites were found in addition to the unchanged drug. In urine, which was the main excretion route for rolipram metabolites, > 10 metabolites were detected but not the parent compound. 4. Between 40 and 70% of the compounds eliminated renally, were identified by reference to isolated metabolites. 5. Biotransformation proceeded by ether cleavage at the methoxy and pentyloxy groups, and by hydroxylation in positions 2 or 3 of the pentyloxy ring followed by sulphation. 6. In man, not in the other species studied, the 5-position of the pyrrolidone ring was also hydroxylated. This compound cross-reacted with the antibody raised against rolipram which was used formerly for the determination of rolipram in biological fluids.

Biotransformation of the antidepressant DL-rolipram. I. Isolation and identification of metabolites from rat, monkey, and human urine

The metabolic pathway of DL-rolipram was studied in two animal species and in man. Metabolites were isolated from rat, rhesus monkey, and from human urine by preparative HPLC and identified by MS and NMR analysis. In total, the structures of 7 degradation products could be elucidated. Rolipram was metabolized by ether cleavage at the methoxy and cyclopentyloxy groups and by hydroxylation in positions 2 or 3 of the cyclopentyloxy ring followed by sulphation. Additionally, but exclusively in man, the 5-position of the pyrrolidone ring was hydroxylated.

Pharmacokinetics of nefiracetam and three metabolites in humans and stereoselective hydroxylation of its pyrrolidine ring

1. The kinetics of nefiracetam (I) and three metabolites (II-IV) were investigated in healthy volunteers. Compounds I-IV in serum and urine were measured by h.p.l.c. 2. After a single 200 mg dose of nefiracetam the drug was absorbed rapidly and showed peak serum levels of 16.3 +/- 0.9 nmol/ml. Cmax values of the three metabolites were comparatively low (0.96-4.89 nmol/ml), and tmax and t1/2 values of the metabolites (4.1-9.6 h and 7.8-21.9 h, respectively) were longer than those of I (1.6 h and 3.9 h respectively). Urinary excretion of I in 24 h was about 5% of the dose. The major urinary metabolite, a pyrrolidine ring scission product (IV), had a mean total excretion of 17.8% dose. The total of all four compounds in urine amounted to 43.4% dose. 3. In a multiple-dose study (daily 3 x 200 mg doses of nefiracetam for 7 days), the serum concentration profile of each compound indicated that the steady state was reached in 7 days. 4. Metabolite II existed as a racemate and III mainly as the (-)-enantiomer in human urine.

High-performance liquid chromatographic procedure for specificity testing of radioimmunoassays: rolipram

A high-performance liquid chromatographic (HPLC) procedure for testing the specificity of radioimmunoassays (RIA) was developed using the same method of extraction as in the RIA, followed by fractionation of the extract by HPLC and subsequent measurement of cross-reactions in all the fractions according to the normal RIA procedure. The RIA of rolipram, an antidepressant drug, was checked in plasma samples obtained from pharmacokinetic studies in rats, rabbits, cynomolgus monkeys and humans. The antibody was shown to be specific in the plasma samples from the laboratory animals, but not in human plasma. This was because in human plasma a metabolite occurred with a structure similar to that used for the hapten in the immunization process. This metabolite was not found in the plasma of the animal species investigated. The test procedure described is generally applicable, making the time-consuming development of an alternative method such as gas chromatography-mass spectrometry unnecessary.

Percutaneous absorption of co-administered N-methyl-2-[14C]pyrrolidinone and 2-[14C]pyrrolidinone in the rat

The percutaneous absorption has been investigated in rats of a mixture (3:2, w/w) of N-methyl-2-pyrrolidinone (NMP) and 2-pyrrolidinone (2-P), a combination intended for use as a vehicle in the formulation of an antimycotic drug to enhance skin penetration on dermal application, following co-administration of the two 14C-radiolabelled compounds by the dermal and oral routes. Radioactivity was excreted predominantly in the urine after either route of administration, and comparison of the respective excretion profiles indicated that about three-quarters of the applied dose was absorbed through the skin. Plasma concentrations of each parent compound, as determined by radio-HPLC, reached peak values at 2 hr after oral dosing, and remained relatively uniform during 1-6 hr after application to the skin, suggesting constant percutaneous absorption during this period. NMP appeared to be absorbed through the skin more extensively and at a slightly faster rate than 2-P; total percutaneous absorption tended to be more extensive in female than in male rats. Together, these two 14C-compounds accounted for most of the plasma radioactivity up to 6-8 hr post-administration. However, by 12 hr (when plasma levels were relatively low), most of the radioactivity was associated with unknown polar metabolites. In view of the extensive percutaneous absorption and little first-pass metabolism of the two pyrrolidinones, the oral route was considered to represent a valid alternative to the dermal route for the assessment of the systemic toxicity of the two compounds.

Investigations on the percutaneous absorption of the antidepressant rolipram in vitro and in vivo

In vitro experiments using full-thickness human skin showed that it was feasible to deliver therapeutic amounts of the new antidepressant drug rolipram. Simple transdermal devices were constructed, and the presence of isopropyl myristate (IPM) in a silicone adhesive (Dow Corning X7-2920) enhanced the flux across excised human skin. The steady-state fluxes from adhesive mixtures containing 0, 5, and 10% IPM were 3, 5.2, and 6 micrograms/cm2/hr, respectively. The in vitro experiments were confirmed in a clinical study involving six healthy male volunteers. The formulations tested were an alcoholic solution and adhesive patches containing 5 and 10% IPM. The dose of drug administered was 0.5 mg/cm2 and the device size 25 cm2. Blood samples were withdrawn over a 24-hr period and analyzed using radioimmunoassay. The topical applications were well tolerated, with only mild or no side effects. A lag time of approximately 2 hr was found for the detection of rolipram in the plasma (detection limit, 50 pg/ml). Interindividual variations both for the peak drug levels and throughout the delivery were quite high but this magnitude of variation has been observed in many other transdermal studies. Plasma levels between 1 and 2 ng/ml were found for all formulations and the AUC0-30 hr was significantly higher for the patch containing 5% IPM.

In-vitro and in-vivo characterisation of two sustained release formulations for the antidepressant rolipram

Using the pellet technology two sustained release formulations for (dl)-rolipram (ZK 62 711; CAS 61413-54-5) were developed and characterised by in-vitro dissolution tests and in a cross-over study in healthy male volunteers. In-vitro, 50% release was achieved within 2.5 h for formulation A and within 4 h for B. In-vivo, Cmax values of 4.4 +/- 0.9 ng/ml (A) and 2.1 +/- 0.8 ng/ml (B) were observed 2.8 +/- 0.8 h or 10.3 +/- 3.7 h after oral intake of 3 mg (dl)-rolipram. The terminal disposition half-life in the plasma was similar for both formulations (12 +/- 13 h and 11 +/- 2 h). Expectedly, the relative bioavailability of formulation B was lower compared to A (72%). Using the pellet technology, formulations with an intended release profile can be tailored to suit by mixing pellets with different release characteristics within one dosage form.

Biotransformation of a new pyrrolidinone cognition-enhancing agent: isolation and identification of metabolites in human urine

1. The metabolites of N-(2,6-dimethylphenyl)-2-(2-oxo-1-pyrrolidinyl)acetamide (DMPPA; MH-1), in the urine of human volunteers have been investigated. 2. Ten metabolites together with the unchanged drug (MH-1) were isolated by h.p.l.c. and identified by n.m.r. and mass spectrometry as: three metabolites hydroxylated in the pyrrolidine ring of MH-1 (MH-2, MH-3 and MH-4), three metabolites hydroxylated in the dimethylphenyl ring of MH-1 (MH-6, MH-7 and MH-8), N-[(2,6-dimethylphenylcarbamoyl)methyl]-4-hydroxybutyrylamide++ + (MH-5), N-[(2,6-dimethylphenyl-carbamoyl)methyl]succinamic acid (MH-9), the 3-O-sulphate of MH-6 (MH-10) and the 3-O-sulphate of N-(2,6-dimethyl-3-hydroxyphenyl)-2-(5-hydroxy-2-oxo-1-pyrrolidinyl)aceta mide (MH-11). 3. DMPPA was extensively metabolized. The principal metabolic transformations were hydroxylation of the pyrrolidine ring at the C5 carbon followed by oxidative C-N cleavage, and hydroxylation of the phenyl ring followed by sulphate conjugation.

Determination of aniracetam and its main metabolite, N-anisoyl-GABA, in human plasma by high-performance liquid chromatography

Two different reversed-phase high-performance liquid chromatographic methods for the determination of aniracetam (I) and its metabolite N-anisoyl-GABA (II) in human plasma are described. The procedure for I involves direct injection of plasma samples spiked with the internal standard on a clean-up column followed by reversed-phase chromatography on a C18 column. The limit of quantification was 5 ng/ml, using a 200-microliters specimen of plasma. The mean inter-assay precision of the method up to 800 ng/ml was 3%. The procedure for II involved liquid-liquid extraction of II and the internal standard from plasma with ethyl acetate, and reversed-phase chromatography on a C18 column. The limit of quantification was 50 ng/ml using a 0.5-ml plasma specimen. The mean inter-assay precision up to 50 micrograms/ml was 6%. The applicability and accuracy of the methods were demonstrated by the analysis of over 1000 plasma samples from two bioavailability studies in healthy volunteers.

The pharmacokinetics of cotinine in plasma and saliva from non-smoking healthy volunteers

Cotinine is a major metabolite of nicotine in man. Its disposition kinetics has been followed in plasma and saliva from nine nonsmokers, 23 to 56 years of age. Cotinine 5, 10 and 20 mg was given intravenously and orally to each subject, and plasma, saliva and urine samples were collected for 96 h. The kinetics of cotinine was best described by a multicompartment model with three distinct phases both in plasma and saliva. Regardless of the mode of administration, there was no indication of dose-dependent kinetics. Mean total plasma clearance was 63.8 ml.h-1.kg-1 and mean renal clearance was 4.7 ml.h-1.kg-1, i.e. only 10% of the dose was excreted unchanged in the urine. The volume of distribution, as calculated from the plasma curves, was slightly greater than the body weight, 1.1 l.kg-1. The concentration of cotinine was 20 to 40% higher in unstimulated mixed saliva than in plasma during the absorption, distribution and elimination phases. As the clearance and distribution values in saliva were directly proportional to the corresponding values in plasma, similar terminal half-life values were obtained in the two body fluids, 15.5 and 16.8 h for plasma and saliva, respectively. Thus the kinetics of cotinine is linear after intravenous and after oral dosing, and salivary concentrations give the same information about cotinine disposition in the body as do plasma concentrations.

Transdermal absorption of radioprotectors using permeation-enhancing vehicles

Radioprotectors are not currently used clinically due to concerns regarding toxicity and uncertainties regarding tumor protection. Topical radioprotection of skin might find clinical applications with protectors such as WR-2721, but laboratory studies in which protectors have been applied in water have not been promising. We have studied the absorption of 14C-WR-2721 and [14C]cysteine dissolved in skin permeation-enhancing vehicles through the skin of hairless mice and compared the absorption to that in water. Skin concentration of WR-2721 was increased most by dimethylformamide (DMF), but only propylene glycol increased absorption as far as the dermis, as measured by plasma concentration. Skin concentration of cysteine was improved by DMF, 2-pyrrolidone (2-P), and methyl-2-pyrrolidone (M-2-P); only dimethylsulfoxide (DMSO) resulted in increased plasma levels of the protector. Pretreating skin with DMSO before application of WR-2721, irrespective of the vehicle, improved its concentration within the skin. Plasma levels were improved (10 and 12 times) only with 2-P and DMF. Therefore, by choosing the appropriate vehicle, it is possible to breach the barrier of the stratum corneum and enhance the presence of the protector in all layers of the skin.

Simulation and evaluation of nicotine intake during passive smoking: cotinine measurements in body fluids of nonsmokers given intravenous infusions of nicotine

The technique of monitoring cotinine concentrations in body fluids as a means of measuring nicotine intake during passive smoking has been evaluated in two studies, both of which used intravenous infusion to stimulate nicotine intake. In the first study, nicotine and cotinine were given separately, for 1 hour in four different intravenous doses (3.2, 15.4, 30.9, and 61.7 nmol/min) to each nonsmoker. In the second study, nicotine and cotinine were infused for 4 hours; each subject received five different doses of nicotine (1.5, 3.1, 6.2, 10.8, and 15.4 nmol/min) and one of cotinine (10.8 nmol/min). The concentration of cotinine was constant in both plasma and saliva from 1 to 4 hours after the nicotine infusion; the plateau levels of cotinine were found to be linearly and directly related to the nicotine intake. The ratio of salivary to plasma cotinine was 1:1.27. A linear relationship was also found between nicotine and cotinine infusion rates and the AUC values for cotinine. The fraction metabolized to cotinine was found to be about 0.5. The results from these studies show that: (1) there is a linear relationship between the plateau concentration of cotinine and the amount of nicotine infused over a period of 1 up to 4 hours; (2) salivary cotinine provides the same information on nicotine intake as does plasma cotinine; and (3) single measurements of either plasma or salivary cotinine concentrations at 1 to 4 hours after the exposure could be used to predict the nicotine intake during 1 to 4 hours of environmental tobacco smoke exposure.

Pharmacokinetics of (+)-rolipram and (-)-rolipram in healthy volunteers

Plasma levels of S-(+)-rolipram and R-(-)-rolipram in six healthy male volunteers were measured by radioimmunoassay after intravenous injection of 0.1 mg and oral administration of 1.0 mg of the pure enantiomers. Following i.v. treatment, plasma levels of both isomers declined in three phases, with half-lives of 0.2 h, 0.6-0.9 h and 6-8 h. Total clearance was 6 ml.min-1.kg-1. Oral administration of 1.0 mg gave a peak concentration of 16 ng.ml-1 after 0.5 h. Bioavailability of (+)-rolipram was 77% and of the (-) enantiomer it was 74%. There was no significant difference in Cmax, half-life, total clearance or bioavailability between the two enantiomers.

Elimination of cotinine from body fluids: disposition in smokers and nonsmokers

We have evaluated differences in the elimination of cotinine, a major nicotine metabolite, in smokers who quit smoking and never-smokers who were exposed to environmental tobacco smoke (ETS) under controlled conditions. The mean biological half-life of cotinine in urine, collected from the nine smokers was 16.5 +/- 1.2 h, in never-smokers exposed to ETS, 27.3 +/- 1.9 h. Differences in the mode of uptake and absorption of nicotine and possible differences in nicotine metabolism may play roles in the clearance rate differences between smokers and nonsmokers.

Pharmacokinetics of the antidepressant rolipram in healthy volunteers

1. The pharmacokinetics of rolipram were studied in healthy male volunteers using 3H-rolipram and a radioimmunoassay for measurement of unchanged drug. 2. Rolipram was rapidly and completely absorbed after an oral dose of 1 mg. Bioavailability was 73%. 3. Plasma levels of the unchanged drug declined with a terminal half-life of 2 h. The total clearance of rolipram was 2 ml/min per kg. 4. Labelled rolipram was excreted rapidly and completely. The main route of elimination was via the urine.

Influence of electrical current on transdermal flux of rolipram

Application of an electrical current is an attractive idea to increase and/or control the transdermal flux of drugs. In order to investigate if transdermal fluxes can be influenced by direct current (DC) and/or alternating current (AC), in vitro studies with the investigational antidepressive rolipram with nude mouse and human cadaver skin using the Chien-Valia diffusion cell were performed. Transdermal flux of rolipram depended on DC polarity and was highest when the epidermal side was positive. Flux increased with time and increasing DC current. Application of DC current led to pH changes which can change dissociation of ionizable substances. Avoiding pH changes by increasing ionic strength of buffer and/or application of AC current increased transdermal fluxes only approximately 2-fold compared to controls.

Saliva cotinine and thiocyanate: chemical indicators of smokeless tobacco and cigarette use in adolescents

Recent attempts to measure smoking behavior using chemical tests may have been confounded by the use of smokeless tobacco. An objective measure of smokeless tobacco use is needed, particularly among adolescents who may not provide accurate self-reports of tobacco usage. Saliva cotinine was used to distinguish self-reported tobacco users from nonusers and a combination of saliva cotinine and thiocyanate (SCN) tests was used to distinguish smokers from smokeless tobacco users. The subjects were 471 students in grades 7 through 11 who lived in a high-tobacco production area. Approximately 89% of reported nonusers had no detectable cotinine and 99% of nonusers had levels less than 25 ng/ml. Of those who had used tobacco within the last 12 hr, 95% had detectable levels of cotinine. Samples that tested positive for cotinine were also tested for SCN. Eighty-six percent of smokers and 74% of mixed users had SCN values of greater than 1000 mumol/liter, while only 14% of smokeless users had SCN values at that level. The combination of cotinine and SCN was effective in distinguishing smokers from smokeless users but was not effective in distinguishing mixed use from the other two types of use.

Brain penetration of orally administered sodium pyroglutamate

The absorption and brain penetration of [3H]pyroglutamate was determined after oral administration to rats. Gas-liquid chromatography of the methylated derivatives followed by mass fragmentometry was used to analyse the plasma and brain levels of pyroglutamate. [3H]Pyroglutamate was separated from other labelled compounds by thin layer chromatography. The administration of 500 mg kg-1 [3H]pyroglutamate resulted in a 30-fold increase in plasma levels and a doubling in the brain levels. Over 60% of the cerebral radioactivity was present as [3H]pyroglutamate demonstrating that pyroglutamate is not only well absorbed but also penetrates in significant amounts into the brain.

Disposition kinetics of nicotine and cotinine enantiomers in rabbits and beagle dogs

The disposition kinetics of nicotine and cotinine enantiomers was determined in rabbits. The clearance of (R)-nicotine was similar to that of (S)-nicotine, but clearance of (R)-cotinine was twice that of (S)-cotinine. Fractional conversions of both enantiomers of nicotine to cotinine were approximately 50%. These results suggest that in rabbits the biotransformation pathways of cotinine, but not nicotine, are influenced by stereochemistry. The disposition kinetics of nicotine enantiomers in beagle dogs was also studied. In dogs, the clearance of (R)-nicotine was slightly greater than the clearance of (S)-nicotine. Methods for the synthesis of (R)-nicotine and (R)-cotinine of high enantiomeric purity and a gas chromatographic method for determination of nicotine enantiomeric purity are described.

Pharmacokinetics of rolipram in the rhesus and cynomolgus monkeys, the rat and the rabbit. Studies on species differences

1. The pharmacokinetics of rolipram were studied in rat, rabbit, rhesus monkey and cynomolgus monkey using 14C- or 3H-labelled rolipram and a radioimmunoassay for measurement of unchanged drug. 2. Rolipram was rapidly and completely absorbed after oral doses of up to 50 mg/kg. Bioavailability was 0.1% in rhesus monkey, 3.7% in cynomolgus monkey, 3.6% in rabbit, 35% in rat, and 75% in man. 3. Rolipram was able to pass the blood-brain barrier achieving concentrations in brain twice those in plasma. 4. Plasma levels of the unchanged drug declined with a similar half-life of 1-3 h in all species investigated. In the rat, there were indications for a different clearance of the two rolipram enantiomers. 5. Labelled rolipram was excreted rapidly and completely. The main route of elimination was via the urine.

Mutagenicity and cytotoxicity of N-methyl-2-pyrrolidinone and 4-(methylamino)butanoic acid in the Salmonella/microsome assay

The industrial solvent N-methyl-2-pyrrolidinone (NMP) and its hydrolysis product, 4-(methylamino)butanoic acid (N-MeGABA), were examined for mutagenicity and cytotoxicity in the Ames Salmonella/microsome assay. In order to detect a broad range of possible mutagenic endpoints, the following strains were used in the assay: base-pair substitution strains TA100, TA102 and TA104; frameshift strains TA97 and TA98; and repair proficient strains TA2638, UTH8413 and UTH8414. In the standard plate incorporation assay, six log-linear doses of each compound were tested; doses ranged from 0.01 to 1000 mumol/plate for NMP, and 0.01 to 316 mumol/plate for N-MeGABA. Neither compound was detectably mutagenic when tested in the presence and absence of metabolic activation by Aroclor-induced rat liver S9. NMP did show significant responses with strains TA102 and TA104 that were less than two-fold over background, but no clear dose-response relationships were evident. A preincubation modification of the assay was also performed, using strains TA98 and TA104. Mutagenic activity was not observed for NMP, while N-MeGABA showed significant responses with TA104 but dose-related mutagenicity was not established. Preincubation testing revealed both NMP and N-MeGABA to be cytotoxic to the test population of Salmonella at the highest treatment doses.

Disposition and metabolism of double-labeled [3H and 14C] N-methyl-2-pyrrolidinone in the rat

The disposition of N-methyl-2-pyrrolidinone (NMP) was studied in the rat using tritium-labeled ([4-3H]NMP) and carbon-14-labeled ([methyl-14C]NMP and [ring-14C]NMP) radioisomers. Male Sprague-Dawley rats were administered a single intravenous dose (45 mg/kg) of 5.0 microCi of 3H or 14C for single-labeled disposition studies or 5.0 microCi of 3H and 2.5 microCi of 14C for double-labeled studies (2:1 ratio, 3H:14C). Plasma levels of intact NMP were analyzed by HPLC through 6 hr after dosing and suggested a rapid distribution phase followed by a slow elimination phase. The half-life for the terminal elimination phase from plasma was about 7 hr for both 14C-isomers and 9.9 hr for the 3H-isomer. The major route of excretion of radioactivity was via the urine and accounted for about 70% of the dose within 12 hr. After 24 hr, cumulative excretion in urine represented about 80% of the dose. The 2:1 ratio of administered 3H:14C was maintained in urine through 6 hr. Measurement of radioactivity in tissues at 6 hr showed the liver and intestines to contain the highest accumulations of radioactivity, representing approximately 2% and 3% of the dose, respectively. Tissue distribution of radioactivity was similar for all three radiolabeled isomers and showed that NMP was extensively distributed to all major organs. Radiomonitored HPLC analyses of urine revealed the presence of one major and two minor metabolites. The major metabolite, representing 70-75% of the administered dose of radioactivity, was found to retain all three radiolabeled positions.(ABSTRACT TRUNCATED AT 250 WORDS)

Influx of a choline analog to dog brain measured by positron emission tomography

The influx of the 11C-labeled choline analog pyrrolidinocholine into tissue was measured in the brain of three dogs by positron emission tomography (PET). During the first 90 s after the intravenous bolus injection of the tracer, transfer of tracer from plasma to tissue was unidirectional. The influx constant for pyrrolidinocholine into intracranial tissue, Kin, was 0.017 ml/g/min (0.008 SD), and the initial volume of distribution, V0, was 0.08 ml/g (0.03 SD). The influx constant was at least five times larger than the value expected if simple diffusion were to account for tissue uptake. The method presented in this paper can be used to investigate the availability of plasma choline and its analogs to the living human brain and other tissue in degenerative diseases affecting the cholinergic system, and to provide in vivo information on a choline transport system.

Constant-rate infusion of nicotine and cotinine. I. A physiological pharmacokinetic analysis of the cotinine disposition, and effects on clearance and distribution in the rat

The tissue partition of cotinine was measured by a GC-MS method following a 6-day constant-rate input of nicotine and cotinine to male rats by means of an osmotic minipump. The tissue-to-blood partition coefficients of cotinine were calculated for adipose (0.08), brain (0.48), heart muscle (0.51), following the cotinine infusion. When nicotine was infused the tissue partitioning of cotinine increased by a factor of 2.3-4.9, depending on the tissue sampled. Another group of animals were killed at timed intervals from 10 min to 30 hr, after having received a single intravenous bolus dose of 0.5 mg cotinine, and the washout of cotinine was traced in blood and tissues. A physiological model was used to simulate the disposition of cotinine. Generally, the model-predicted concentrations were consistent with those found experimentally. The fractional uptake of cotinine into various tissues was simulated. Blood, intestinal, and skeletal muscle tissues embodied more than 70% of the total body load of the drug. Clearance (Cl), volume of distribution (Vd), and the biological half-life (t1/2) were calculated both from the infusion study and by fitting a monoexponential model to the iv blood data of the rat. Significant differences were found in the apparent clearance calculated from the single iv bolus dose compared to the constant rate infusion. The volume of distribution was, however, consistent from both studies. The impact of a change in clearance was also simulated.