Ther Drug Monit. 1993 Aug;15(4):267-73.
Distribution of amitriptyline and nortriptyline in blood: role of alpha-1-glycoprotein.

Amitai Y, Kennedy EJ, DeSandre P, Frischer H.

Department of Pharmacology (Section of Blood Genetics and Pharmacogenetics), Rush-Presbyterian St. Luke's Medical Center, Rush University, Chicago, Illinois 60612.

To interpret blood levels of tricyclic antidepressants, we studied the distributions of amitriptyline and nortriptyline in human blood and explored their control by plasma factors. Each compound (300 ng/ml) was added to whole adult blood and to cord blood with decreased alpha-1-glycoprotein (AGP). Drugs (250 ng/ml) were also added to washed erythrocytes (RBCs) resuspended in autologous plasma or saline (hematocrit = 0.4) with or without AGP, albumin, or tris(2-butoxyethyl) phosphate (TBEP), used to displace AGP-bound drugs. Plasma AGP was determined in all adult blood donors (n = 17). With adult blood, plasma amitriptyline was 393 +/- 52 ng/ml, RBC amitriptyline was 184 +/- 33 ng/ml. Plasma and RBC nortriptyline were 199 +/- 28 and 288 +/- 39 ng/ml, respectively. With saline, cellular amitriptyline and nortriptyline were 81 +/- 10 and 88 +/- 6%, respectively. With plasma, cellular amitriptyline and nortriptyline were 25 +/- 8 and 49 +/- 10%, respectively. The corresponding cord blood values were 52 +/- 12 and 62 +/- 6%. Graded increments of AGP in saline reproduced the distribution pattern seen with increasing concentrations of plasma. Albumin did not influence drug distribution. TBEP markedly increased erythrocyte amitriptyline in adult but not in cord blood. Plasma AGP correlated positively (p = 0.031) with the RBC/plasma ratio of amitriptyline. Amitriptyline is predominantly distributed in plasma, nortriptyline in RBCs. This differential distribution is dose dependent and reflects the higher binding of amitriptyline to AGP when compared with nortriptyline. Interpretation of tricyclic antidepressant blood levels is clarified by obtaining assays from RBCs and plasma.

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Acta Psychiatr Scand Suppl. 1983;308:131-4.
A comparison of zimeldine and amitriptyline on cardiovascular effects in healthy volunteers.

Wester HA.

The cardiovascular effects of zimeldine (200 mg) and amitriptyline (150 mg) for 6 days were compared in a study involving 10 healthy volunteers. No significant changes were found in heart rate, mean arterial blood pressure or left ventricular contractility when patients were taking zimeldine. With amitriptyline, significant changes were seen at some point during the trial period for all these parameters. No significant changes were seen in the ECGs recorded. Thus, zimeldine appears to be free of adverse effects on contractility, but amitriptyline appears to have a negative inotropic effect.

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Yao Xue Xue Bao. 1993;28(2):85-91.
[Relationship between amitriptyline metabolism and polymorphic debrisoquine hydroxylation in native Chinese volunteers]

[Article in Chinese]

Zhang XH, Yu P, Gu NF, Yin JL, Jiang WD.

Department of Psychiatry, Shanghai Medical University.

The demethylation and hydroxylation of amitriptyline were calculated from the ratios between the area under concentration--time curve (AUC) of amitriptyline and its three metabolites in eight healthy Chinese volunteers after a single oral dose of 100 mg amitriptyline. Great interindividual differences in AUCs of amitriptyline and its metabolites were observed. HPLC method was used to determine the debrisoquine hydroxylation phenotype in seven out of the eight volunteers. Six subjects were found to be rapid and one slow debrisoquine hydroxylators. The ratio between debrisoquine and 4-hydroxydebrisoquine in urine correlated significantly with the rate of amitriptyline hydroxylation and the AUCs of amitriptyline and 10-hydroxy amitriptyline, but not with that of amitriptyline demethylation. There also was a weak correlation between total plasma clearance and the hydroxylation of debrisoquine. These data suggest that the hydroxylation of amitriptyline and debrisoquine may be regulated by similar enzymatic processes and the demethylation and hydroxylation processes in amitriptyline metabolism appear to undergo two separate pathways.

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Am J Forensic Med Pathol. 1993 Jun;14(2):118-20.
Drug analysis in fly larvae.

Wilson Z, Hubbard S, Pounder DJ.

Department of Forensic Medicine, University of Dundee, Scotland.

We reared larvae of Calliphora vicina on human skeletal muscle obtained from cases of suicidal overdose with co-proxamol (propoxyphene and acetaminophen) and amitriptyline. After 4 days, third-instar larvae were either transferred to drug-free muscle or continued to feed on drug-laden muscle for a further 2 days prior to harvesting. Amitriptyline and nortriptyline were detected in both groups of larvae, but propoxyphene was only in those fed continuously on drug-laden muscle, and acetaminophen was in neither. Drug concentrations in muscle food source were amitriptyline 0.48 microgram/g, nortriptyline 0.38 microgram/g, propoxyphene 0.99 microgram/g, and acetaminophen 14.13 micrograms/g. For triplicate rearings, the mean ratios of drug concentrations in larvae to food source were amitriptyline, 0.56; nortriptyline, 0.5; and propoxyphene, 0.06. In triplicate rearings, no drug or metabolite was detected in puparia, puparial cases, or imagos. We conclude that the absence of a drug in maggots is not necessarily an indication that the drug was not present in significant concentrations in the food source. The malpighian tubules and the "nephrocytes" of fly larvae appear capable of eliminating different drugs with varying efficiency.

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Pharmacol Biochem Behav. 1983 May;18(5):737-40.
Bupropion, d-amphetamine, and amitriptyline-induced conditioned taste aversion in rats: dose effects.

Miller DB, Miller LL.

Nine groups of rats (n = 6 per group) were adapted to a daily one-half hour period of water availability. When intake had stabilized, they were allowed access to a 0.1% (w/v) solution of saccharin, and immediately afterward were given IP injections of isotonic saline; bupropion HCl (10.0, 20.0, or 40.0 mg/kg); d-amphetamine-sulfate (0.5, 1.0, 2.0 mg/kg); or amitriptyline HCl (5.0, 10.0, or 20.0 mg/kg) in a volume of 1 ml. The lowest dose of each compound as chosen to be equipotent in screening tests used to identify potential antidepressants. Following 2 days of access to water alone, all groups were given a choice between water and saccharin for 3 consecutive days. All compounds induced taste aversions in a dose-related manner, but amitriptyline induced greater and longer-lasting aversions than either bupropion or d-amphetamine which were equipotent over the dose range studied. As such, this is the first demonstration that bupropion and amitriptyline, two clinically effective antidepressants, can induce taste aversions and replicates as well the common finding that d-amphetamine has substantial taste aversion-inducing properties. The ability of these compounds to induce taste aversions could be mediated through their effects on central catecholaminergic processes although amitriptyline has significant peripheral anticholinergic effects.

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J Toxicol Clin Toxicol. 1993;31(3):461-71.
Effects of epinephrine and norepinephrine on hemodynamic parameters and arrhythmias during a continuous infusion of amitriptyline in rats.

Knudsen K, Abrahamsson J.

University of Goteborg, Sweden.

Epinephrine and norepinephrine were evaluated in treatment of hemodynamic compromise in amitriptyline intoxication. One hundred and one male Wistar rats were monitored hemodynamically during amitriptyline intoxication and given one of three infusion rates (0.1, 0.5 or 5.0 mg/kg/min) of either epinephrine or norepinephrine. Sixteen rats served as controls and received only glucose after intoxication. Amitriptyline intoxication lowered mean arterial pressure, heart rate, left ventricular max dP/dt, and increased left ventricular end-diastolic pressure. All doses of norepinephrine and the two higher doses of epinephrine increased mean arterial blood pressure and left ventricular max dP/dt. Heart rate increased with both drugs, more with epinephrine, but not beyond pre-intoxicated levels at any dose. Left ventricular end-diastolic pressure was unaltered by both drugs. Malignant arrhythmias appeared in 7% of all animals, whereas a progressive decline of cardiac contractility caused cardiac arrest in 36% of all animals. This suggests that myocardial depression is the aspect most likely to cause death. At intermediate doses epinephrine resulted in significantly fewer arrhythmias and lower mortality compared to norepinephrine. We conclude that epinephrine and norepinephrine each appeared effective in reversing amitriptyline-induced hemodynamic alterations. Epinephrine had fewer arrhythmogenic properties than norepinephrine and may be preferable to norepinephrine.

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Rom J Neurol Psychiatry. 1993 Jan-Mar;31(1):11-9.
The influence of amitriptyline and flunarizine on catecholamine response to light in patients with migraine.

Stoica E, Enulescu O.

Institute of Neurology and Psychiatry, Bucharest, Romania.

The effect of amitriptyline on catecholamine (CA) response to light of 20 migrainous patients was studied. The drug was given orally, 36 mg daily (12 mg x 3), for ten days. Before therapy, the migraineurs responded to light by an increase in epinephrine (E) excretion and not by the rise in norepinephrine (NE) excretion, noticed in controls. The NE excretion of migrainous subjects underwent very often a depression after photostimulation. Amitriptyline therapy prevented the post-photic rise in E excretion of migraineurs, without influencing significantly the variation in NE excretion produced in them by light. In other 8 migrainous subjects the effect of flunarizine, a selective calcium channel blocker, on CA response to light was tested. The dosage was of 5 mg daily, for ten days. Flunarizine had similar effects to those displayed by amitriptyline; the drug prevented the rise in E excretion produced by light without normalizing the NE response to light of migrainous subjects. The results suggest that the efficiency of these two drugs in migraine prophylaxis is connected with the ability of these substances to block the E discharge produced in migraineurs by light or by other stimuli. The interpretation is all the more likely as propranolol, another drug applied in migraine prophylaxis also blocks the post-photic E discharge of migraineurs.

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