Tissue distribution of chlorimipramine and its demethylated metabolite after a single dose in the rat

Regional distribution of clomipramine and desmethylclomipramine in rat brain and peripheral organs on chronic clomipramine administration

The tricyclic antidepressant (TCA) clomipramine has been widely used in psychiatry for over 40 years. More recently, its therapeutic potential as an antineoplastic drug has been identified. However, there are no prior data on regional distribution in the brain of clomipramine and its primary metabolite (desmethylclomipramine) after chronic oral administration. The aim of this study was to determine the concentrations of clomipramine and desmethylclomipramine in different rat-brain regions and to compare those with levels in plasma and peripheral organs after chronic oral treatment of Sprague Dawley rats (15 mg/kg) for 14 days. The levels of both parent TCA and metabolite were analysed by high-performance liquid chromatography in six brain regions (cortex, hypothalamus, hippocampus, striatum, brainstem and cerebellum), five peripheral organs and in plasma. Our data show that the cerebral cortex had the highest concentration of clomipramine (2.9 microg/mg), with successively lower concentrations in the hypothalamus, striatum, cerebellum, hippocampus and brainstem. Of the peripheral organs, the lungs and liver, had the highest levels of clomipramine, while in the heart, only the metabolite was detected. The plasma concentration (0.17 microg/ml or 0.48 microM) was comparable to that in the hippocampus and cerebellum (approximately 0.20 microg/mg). The differential distribution of clomipramine in different brain regions and the regional variation in clomipramine to desmethylclomipramine ratios have implications for the use of clomipramine in psychiatry and neuro-oncology.

Treatment of severe tricyclic antidepressant overdose with extracorporeal sorbent detoxification

Tricyclic overdose can be a medical emergency, and therapy with intravenous bicarbonate is not always successful in preventing cardiac toxicity or coma. Mortality in patients developing these complications is from 1% to 15%. Extracorporeal detoxification with sorbents has been used in treatment of patients with very high drug levels and declining clinical condition. Ten patients with serious drug overdose caused by tricyclics failed to respond quickly to standard therapy and were in stage 3-4 encephalopathy. Nine of these patients were on respirator support, 5 had hypotension, and 6 had QRS widening. Average level was 1,423 microg/L at presentation. Enteral activated charcoal and intravenous (IV) bicarbonate were initiated in the emergency room. The patients were treated for 3 to 4 hours with the Liver Dialysis Unit, a hemodiabsorption device using a cellulosic plate dialyzer and sorbent suspension as dialysate. Inflow and outflow blood levels indicated that the hemodetoxifier removed modest amounts of the tricyclics, metabolites, and other consumed drugs. The clinical improvement of the patients was dramatic, with patients reaching stage 0 or 1 encephalopathy during the treatment. Ventilator support was removed at the end of treatment for 3 patients who had not already developed pneumonia, and for others was prolonged up to 48 hours because of pneumonia, rather than mental status. Average length of stay in the intensive care unit (ICU) was 4.8 days (range 1 to 7 days). None of the patients died despite their high risk for ventricular arrhythmias, seizures, and death. Clinical improvement may have been attributable to removal of free drug from the blood or to removal of drug metabolites.

The tricyclic antidepressant clomipramine dose-dependently reduces regional cerebral metabolic rates for glucose in awake rats

The time course and the relation to dose of regional cerebral metabolic rates for glucose (rCMRglc) were measured in awake male Fischer-344 rats after administration of clomipramine (CMI), a serotonin (5-HT) uptake inhibitor and clinical antidepressant. rCMRglc was determined, using the quantitative autoradiographic [14C]2-deoxyglucose technique, in 64 brain regions at 20, 40, 60, 120, and 180 min after administration of CMI 50 mg/kg IP and 120 min after CMI 2 and 10 mg/kg IP. The peak metabolic effect was observed at 120 min after CMI. At that time, CMI 2 and 10 mg/kg IP significantly reduced rCMRglc from control values in 12 (19%) and 14 (22%) brain regions, which correspond to areas with high densities of 5-HT reuptake sites (e.g. visual and limbic areas and raphe nuclei). CMI 50 mg/kg produced widespread rCMRglc reductions in 34 (53%) brain regions, including cortical, hippocampal, raphe and cerebellar areas. The topographic distribution and the relation to time and dose of CMI effects on rCMRglc are different from those of 5-HT1A [8-hydroxy-2(di-N-propylamino) tetralin], 5-HT1B-C (m-chlorophenylpiperazine) and 5-HT3 (quipazine) agonists and resemble those produced by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), an agonist of 5-HT2 receptors, suggesting that CMI may prefentially stimulate this 5-HT receptor subtype.

Compared plasma and brain pharmacokinetics of clomipramine and its metabolite demethylclomipramine in two strains of mice (NMRI and CD1)

The fate of clomipramine (CMI) and its main demethylated metabolite demethylclomipramine (DCMI) was studied in two strains of Swiss mice (NMRI and CD1) after intraperitoneal injection. A study of its distribution among various tissues showed that fixation was most marked in lungs, perirenal fat and kidneys, and only moderate in the brain. The pharmacokinetic parameters of both molecules were determined in brain tissue and plasma. Absorption was rapid (tmax CMI = 14 min), metabolism prompt (tmax DCMI = 17 or 18 min according to the breed) and elimination rapid from both plasma and brain tissue. The first two stages were similar in the two strains, but elimination of CMI from both plasma and brain was faster in the NMRI mice (plasma t1/2 = 53 min against 165 min in the CD1 mice). Both values were well below that reported for man (mean plasma t1/2 = 24 h). The data presented can serve as a basis for designing true chronic administration protocol in animals.

Modification of the antinociceptive effect of morphine by acute and chronic administration of clomipramine in mice

The antinociception effect of clomipramine and the combination of clomipramine and morphine was evaluated using the constant temperature hot plate test, the increasing temperature hot plate test and the formalin test in mice. Both a single dose of clomipramine (10 mg/kg) given intraperitoneally (i.p.) and chronic clomipramine treatment (10 mg/kg/day, i.p., for 7 days) induced antinociception. When morphine (5 mg/kg), given subcutaneously (s.c.), and clomipramine were combined, an increased antinociceptive effect compared to morphine alone was observed in all tests. In the increased temperature hot plate test and in the formalin test increased antinociception was also observed when morphine was combined with chronic clomipramine treatment. In the constant temperature hot plate test no additional effect compared to morphine alone was observed when morphine and chronic clomipramine treatment were combined. These results indicate that clomipramine has an antinociceptive effect in itself, and that it may enhance the antinociceptive effects of morphine. The differences between the tests indicate that different nociceptive mechanisms are involved, and that the combination of clomipramine and morphine may be beneficial for some types of nociceptive stimuli, but not for others.

Physiological pharmacokinetics and pharmacodynamics of (+/-)-verapamil in female rats

Tissue distribution and pharmacodynamics of verapamil were evaluated during steady state intravenous (i.v.) infusion and after single dose intraperitoneal (i.p.) drug administration to female Sprague-Dawley rats. In one group of rats, verapamil was infused to a steady state concentration at which time animals were killed. Verapamil-induced decreases in mean arterial pressure (MAP) were monitored during infusion and correlated with concomitantly obtained plasma verapamil concentrations. Tissue (lung, liver, renal medulla, renal cortex, cardiac muscle, skeletal muscle, perirenal fat, brain stem, cerebral cortex, and cerebellum) and plasma samples were obtained immediately after animals were killed and verapamil and norverapamil concentrations determined. Another group of rats, after receiving i.p. verapamil, were killed at 1, 3, 5, 19, and 24 h. Elimination from each tissue evaluated was described by a first order process. Elimination half-life of verapamil was similar among plasma and tissues evaluated (1.5 to 2.2 h). The per cent verapamil not bound to plasma proteins was concentration-independent and similar between rats receiving i.p. (mean +/- S.D.) (2.28 +/- 0.72 per cent) and i.v. (2.08 +/- 0.03 per cent) verapamil. MAP and verapamil concentration in plasma (r = 0.75; p less than 0.01) and cardiac muscle (r = -0.82; p less than 0.01) were inversely correlated in a highly significant fashion during both i.v. and i.p. drug administrations. The tissue-to-plasma distribution ratio for verapamil and norverapamil was similar among animals receiving i.p. verapamil at all points of sampling, suggesting distribution equilibrium had been achieved. After steady state i.v. infusion, both verapamil and norverapamil tissue: plasma concentration ratios were greater than after i.p. administration. Higher tissue: plasma verapamil concentration ratios after i.v. administration than after i.p. administration suggest either only a pseudoequilibrium is attained after i.p. administration or that determinants of tissue distribution of racemic verapamil differ with different routes of drug administration. In these studies, MAP provided a reasonable pharmacodynamic marker for verapamil tissue and plasma concentrations.