Effect of Renal Impairment on the Pharmacokinetics and Tolerability of Tiagabine

Summary: Purpose: We wished to determine the effect of renal impairment on the pharmacokinetics and tolerability of the new antiepileptic drug tiagabine (TGB).
Methods: We assessed TGB pharmacokinetics and tolerability in 25 subjects with various degrees of renal function (based on creatinine clearance, n = 4–6 per group) from healthy (group I) to requiring hemodialysis (group V) in a single and multiple dose (every 12h), one-period (groups I-IV) or a single dose, two-period (group V) study (4-mg oral doses of TGB · HCl). Blood samples were collected after the first dose (both periods for group V) and after the last dose on day 5 (groups I-IV). TGB plasma concentrations and plasma protein binding were determined by high-performance liquid chromatography (HPLC) and ultrafiltration, respectively.
Results: TGB was well tolerated by all study subjects. The pharmacokinetics of TGB were similar in all subjects; no pharmacokinetic parameter (based on either total or unbound concentrations) was statistically correlated with creatinine clearance. For total TGB in plasma, single-dose mean values of the maximum plasma concentration, clearance, and half-life (t1/2) ranged from 52 to 108 ng/ml, from 7.14 to 11.02 I/h, and from 6.4 to 8.4 h, respectively.
Conclusions: TGB pharmacokinetics and tolerability were independent of renal function; therefore, dosage adjustment is unnecessary for epilepsy patients with renal impairment.     

Glycopyrrolate vs. atropine during anaesthesia for laryngoscopy and bronchoscopy

As glycopyrrolate has been reported superior to atropine with respect to reduction of salivation, stability of cardiac rate and rhythm, and recovery, a comparison of these properties of the two drugs and placebo was made in 45 patients undergoing direct laryngoscopy and 45 patients undergoing bronchoscopy, in most cases followed by mediastinoscopy. When given i.m. 30 min before anaesthesia (midazolam, alfentanil, thiopentone, and suxamethonium), the two test drugs were found to be equally potent regarding the antisialogogic effect. The same increase in heart rate after the test drugs was seen before induction, and during anaesthesia heart rate rose to the same level in the placebo group as the test groups. During anaesthesia, blood pressure was lowest in the atropine group. No differences could be demonstrated with respect to cardiac arrhythmias, possibly due to the small size of the material. The present study gives no reason for preferring either drug, and only the efficacy of both test drugs in controlling airway secretions provides an argument for using any anticholinergic drug when laryngoscopy or bronchoscopy is performed under the conditions of the present study.     

Endocrinology: Two cases of ovarian tumours in women who had undergone multiple ovarian stimulation attempts

Concerns have been raised recently about the possible associationbetween superovulation and ovarian cancer. In order to contributeto the limited literature on this important issue, two casesof ovarian tumours in women who had undergone multiple ovulationinductions are presented. In the first case, the patient hadsecondary anovulatory infertility. She was treated with humanmenopausal gonadotrophin (HMG) alone and in combination withclomiphene citrate or buserelin for six cycles. She then underwentovarian stimulation with buserelin/HMG in the long protocolfor in-vitro fertilization (IVF) and embryo transfer. In preparationfor a new IVF/embryo transfer attempt, 8 months later, the screeningultrasound revealed a cystic formation of the left ovary andan enlargement of the right. During laparotomy, both ovarieswere found to bear large tumours (approximately 6x5x4 cm) whichwere removed. Histological examination showed that they wereepithelial tumours (serous-papillary cystadenomas) of borderlinemalignancy. The patient conceived spontaneously 1.5 years afterthe operation. In the second case, the patient presented withsecondary anovulatory infertility. She underwent ovulation inductionwith clomiphene/HMG and with buserelin/HMG in the long protocol,and intra-uterine insemination with husband's spermatozoa andconceived (singleton pregnancy). She was delivered by Caesareansection, during which a cystic tumour of the left ovary wasremoved. Histological examination revealed a benign mucous cystadenomaof the ovary. In conclusion, the clinical information from thesetwo cases does not support a causal association between ovarianstimulation and ovarian tumours but does potntially supporta facilitating one.     

Selective inhibition of MAO-A,not MAO-B,results in antidepressant-like effects on DRL 72-s behavior

The effects of monoamine oxidase inhibitors (MAOIs) that selectively inhibit the MAO-A or MAO-B forms of MAO were studied in rats performing under a differential-reinforcement-of-low-rate 72-s (DRL 72-s) schedule of reinforcement. Clorgyline and CGP11305A, irreversible and reversible MAO-A inhibitors, respectively, increased the reinforcement rate, decreased the response rate, and enhanced temporal discrimination. The irreversible MAO-B inhibitor (–)-deprenyl did not produce similar effects. Pargyline did not increase the reinforcement rate at low doses that selectively inhibit MAO-B, but did increase the reinforcement rate at doses that inhibit MAO-A by more than 90%. The present results are in accord with clinical data demonstrating that MAO-A inhibitors are effective therapeutic agents in treating depression while MAO-B inhibitors are of questionable antidepressant efficacy. The present findings provide further evidence that the DRL 72-s schedule may be useful both as a screen for identifying new antidepressants and for investigating the neurochemical effects of antidepressant drugs that are responsible for their therapeutic effects.     

Dose-response curves of homovanillic acid in pre-frontal cortex and caudate following antipsychotic drugs: relation to clinical potencies

Dose-response curves for the elevation of homovanillic acid (HVA) levels, determined by high performance liquid chromatography using electrochemical detection, in the pre-frontal cortex and caudate of rats after acute treatment with 12 antipsychotic drugs are presented. The order of potency in both brain regions was: haloperidol fluphenazine > loxapine > trifluoperazine > thiothixene > molindone > clopenthixol > chlorpromazine > metoclopramide > thioridazine > clozapine > sulpiride. This ranking is roughly correlated with that based on clinical potencies. The relative elevation of the content of HVA was weaker in the pre-frontal cortex than in the caudate for all drugs tested, except clozapine at a high dose.     

肥胖相关性肾病诊疗研究进展

肥胖相关性肾病已呈流行发展趋势,已成为终末期肾病的主要原因之一。目前认为其发病机制主要与肥胖所致肾小球血流动力学改变和脂质异位沉积等相关,但其机制仍未完全阐明。减轻体重是治疗肥胖相关性肾病的重要方法,但常因环境、个人执行情况的影响而收效甚微,且有部分患者体重控制后肾病仍持续进展。综合应用有效的肥胖相关性肾病治疗方法,对控制其进展十分重要。该文综述肥胖相关性肾病的致病机制和诊疗进展,探讨中药在肥胖相关性肾病治疗中的价值,旨在为临床提供参考,提高肥胖相关性肾病一体化管理水平。     

Differential potentiation by calcium antagonists of neuromuscular blockade induced by pancuronium and succinylcholine in cats in vivo

Summary The effects of several calcium antagonists (verapamil, nicardipine and two diltiazem isomers, d-cis and l-cis diltiazem) alone and associated to non-depolarizing (pancuronium) and depolarizing (succinylcholine) neuromuscular blockers, were evaluated on sciatic nerve-tibialis anterior muscle preparations from cats in vivo. The calcium antagonists used (at 0.1 and 0.5mg/kg iv) did not modify the height of muscular twitches elicited indirectly. However, these agents potentiated in a dose-dependent way the neuromuscular blockade induced by iv pancuronium (2–40g/kg) and succinylcholine (6–200g/kg). The order of potency in increasing the effects of pancuronium was nicardipine d-cis diltiazem verapamil, whereas the order of potency in enhancing succinylcholine effects was d-cis diltiazem verapamil nicardipine. The effects of diltiazem were stereoselective, thus the potentiation induced by d-cis diltiazem was significantly greater in all cases than that induced by l-cis diltiazem, which suggests that calcium channel blockade plays a role in these interactions. However, other mechanisms such as calcium antagonists-induced nicotinic receptor desensitization may also be involved.     

Specific modulation of social memory in rats by cholinomimetic and nootropic drugs,by benzodiazepine inverse agonists,but not by psychostimulants

The recognition of an unfamiliar juvenile rat by an adult rat has been shown to imply short-term memory processes. In this study the effect of various psychotropic drugs on this investigatory behaviour was examined. The procedure was as follows: an unfamiliar juvenile rat was placed in the home cage of an adult rat for 5 min. The time spent by the adult rat in investigating the juvenile was recorded. The adult rat was then immediately treated with vehicle or test compounds, and was again exposed for 5 min to the same juvenile 2 h later. At this time point vehicle-treated rats no longer recognized the juvenile rat, i.e. the time of investigation was similar to that observed during the first presentation. Arecoline (1 and 3 mg/kg IP), physostigmine (0.05 and 0.1 mg/kg SC), RS86 (0.5 mg/IP) and nicotine (0.125 and 0.5 mg/kg IP) reduced in a dose-dependent fashion the time spent in investigating the juvenile during the second exposure. This result cannot be attributed to nonspecific effects, since it was not observed when a different juvenile was used for the second exposure. The effect of arecoline was reversed by scopolamine, but not by methylscopolamine. Aniracetam reduced investigatory behaviour at the dose of 50 mg/kg IP. FG 7142 (5 mg/kg IP) and -CCM (0.4 mg/kg IP) were also active and their effect was reversed by Ro 15-1788. dl-Amphetamine (0.5 and 1 mg/kg IP), nomifensine (1.25–10 mg/kg IP) and strychnine (0.25 and 0.5 mg/kg IP) were ineffective or reduced this behaviour unspecifically. Social recognition may therefore represent a useful and simple test to detect compounds which enhance short-term, olfactory, memory and to assess in the same animals the specificity of this activity.     

Pharmacokinetic study of iminodibenzyl antipsychotic drugs,clocapramine and Y-516 in dog and man

The pharmacokinetic properties of the iminodibenzyl antipsychotic drugs clocapramine (CCP, 3-chloro-5-[3-(4-carbamoyl-4-piperidino piperidino) propyl]-10, 11-dihydro-5H-dibenzo[b, f]azepine) and Y-516 (3-chloro-5-[3-(2-oxo-1, 2, 3, 5, 6, 7, 8, 8a-octahydroimidazo [1,2-a] pyridine-3-spiro-4-piperidino) propyl]-10, 11-dihydro-5H-dibenzo[b, f]azepine) were investigated in dog and man. Dogs were administered CCP and Y-516 intravenously, intraperitoneally, and orally, and the concentrations of the parent drugs and their metabolites in the plasma and urine were determined. Half-life (t1/2) was approximately the same by all three administration routes, being approximately 5 h for CCP and 3 h for Y-516. Bioavailability following oral administration was 0.16±0.01 (mean ± SD, n=3) for CCP and 0.29±0.07 for Y-516. The fractions of dose absorbed following oral administration were 0.43±0.07 and 0.79±0.24, and the fractions of dose metabolized in the liver due to the first-pass effect were 0.63±0.05 and 0.63±0.04 for CCP and Y-516, respectively. Y-516 was detected in the plasma after intraperitoneal and oral administration of CCP. The ratio of the AUC of Y-516 to that of CCP was 0.06 following intraperitoneal administration and 0.40 following oral administration. This indicated that while the metabolism of CCP into Y-516 may occur partly in the liver due to the first-pass effect, it occurs mostly within the gastrointestinal tract itself or its mucosa. When CCP and Y-516 were given orally to man, the plasma concentrations of both parent drugs increased in a dose-dependent manner. The t1/2 of CCP at a dose of 50 mg was 46±6 h (n=3) while that of Y-516 at a dose of 25 mg was 15±2 h (n=5), so that elimination from the circulation was slower than in the dog in both cases. As in the dog, Y-516 was detected in the plasma following administration of CCP, but its concentration was approximately one fifth that of CCP and lower than that found in the dog. From the ratios of Y-516 produced upon oral administration of CCP in dog and man, we concluded that Y-516 is involved to a considerable degree in the pharmacological action of CCP in the dog and, though to a lesser degree, in man as well.     

Drug Binding to α1-Acid Glycoprotein Studied by Circular Dichroism

The interactions of acidic and basic drugs with ₁-acid glycoprotein (₁-AGP) were investigated using circular dichroism (CD) measurements. Extrinsic Cotton effects were generated by the binding of drugs to ₁-AGP. The CD data suggested the presence of a single binding site on the ₁-AGP molecule. The induced ellipticities of the acidic drug–₁-AGP system decreased with increasing pH, while the ellipticities for the basic drugs increased with pH. The ellipticities for all drugs were reduced by the addition of fatty acids. Furthermore, the induced ellipticities decreased in the presence of cesium chloride for basic drugs bound to ₁-AGP. The extrinsic Cotton effects therefore appear to result from hydrophobic interaction with ₁-AGP for the acidic drugs and from hydrophobic and electrostatic interactions for the basic drugs.