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Cardiovascular effects of amitriptyline, nortriptyline, protriptyline, and doxepin in conscious rabbits after subacute pretreatment with protriptyline.

Conscious rabbits which had been permanently catheterized into their aortas and posterior caval veins, were injected daily with 10 mg/kg of protriptyline subcutaneously, divided in 3 doses. The blockade of the membrane pump in sympathetic nerve terminals by protriptyline was checked by pressor tests with noradrenaline (NA) and tyramine. In the presence of the membrane pump blockade 2.5 mg/kg of amitriptyline, nortriptyline, or protriptyline, or 3.0 mg/kg of doxepin was injected i.v. The antidepressants lowered blood pressure transiently and increased the heart rate, doxepin and amitriptyline being more effective than nortriptyline and protriptyline. Amitriptyline and doxepin provoked more severe cardiac arrhythmias on ECG than nortriptyline, and protriptyline caused no arrhythmias. Intravenous infusion of NA (11 mug/min) raised the blood pressure and lowered the heart rate. Injection of antidepressants during NA infusion resulted in more pronounced depressor and tachycardic effects than occurred without NA infusion. Major ECG changes were only slightly more apparent than without NA infusion. The rank order of toxicity of the antidepressants was the same. It is concluded that the NA potentiation by tricyclic antidepressants is not the main reason for their cardiotoxic effects.

Amitriptyline

Protriptyline kinetics.

The kinetics of protriptyline were examined in 8 subjects after a single oral dose of 30 mg protriptyline hydrochloride. Peak protriptyline levels ranged from 10.4 to 22.3 ng/ml and were reached 6 to 12 hr after the oral dose. The mean protriptyline half-life (t1/2) was 74.3 hr and ranged from 53.6 to 91.7 hr in individual subjects, confirming the long t1/2 of protriptyline reported by Moody and associates. The estimated first-pass metabolism of protriptyline was relatively small, ranging from 10% to 25% of the oral dose, assuming complete absorption. The mean volume of distribution was 22.5 L/kg and ranged from 15.0 to 31.2 L/kg. No relationship was found between the kinetics of protriptyline and those of doxepin studied previously in 7 of the 8 subjects.

Adult

Further characterization of reversal of signs of induced cotton effects of dicumarol derivatives-alpha 1-acid glycoprotein systems by protriptyline.

The interaction of dicumarol derivatives and protriptyline with respect to the binding to alpha 1-acid glycoprotein (AGP) has been investigated by circular dichroism (CD), equilibrium dialysis and ultrafiltration. Investigation of the induced CD spectra of dicumarol derivatives bound to AGP indicated that the conformations of these compounds were different when bound to AGP. Though all the dicumarol derivatives, protriptyline and AGP formed a ternary complex, interaction modes were different, depending upon the substituent groups at position 3 of the dicumarol molecule. On the basis of the protriptyline effect on the CD spectra of all dicumarol derivatives bound to AGP, the compounds were classified in the following way: (1) Dicumarol, ethylidenebis 4-hydroxycoumarin and propylidenebis 4-hydroxycoumarin caused reversal of the sign of ellipticity. This interaction was explained by cooperative binding. (2) Butylidenebis 4-hydroxycoumarin and pentylidenebis 4-hydroxycoumarin generated new band and disappeared ellipticity of the original Cotton effect. This interaction was also explained by the cooperative binding mode. (3) Ethylbiscoumacetate which generated the CD band similar to that of dicumarol in the absence of protriptyline, reversed the sign of the CD spectrum only at 325 nm. The interaction was anticooperative in nature. (4) Benzylidenebis 4-hydroxycoumarin represented type four which had no change in the CD spectrum by the addition of protriptyline. This interaction was explained by the two-state model accompanying the conformational change of AGP. These results suggested that all compounds, except for benzylidenebis 4-hydroxycoumarin, induced negative Cotton effects at 325 nm by taking the same asymmetrical perturbation by the addition of protriptyline and the interaction was carried out according to model 2. An attempt to study the interaction mechanism of two or more drugs with regard to the binding to protein using these models is thought to help in understanding drug-protein interactions.

Binding Sites

Plasma concentrations and cardiotoxic effects of desipramine and protriptyline in the rat.

1 Desipramine and protriptyline were administered to anaesthetized rats by two consecutive intravenous infusions in order to obtain a peak level (first infusion) followed by lower steady state concentrations (second infusion) (Wagner, 1974). Theoretical plasma level time courses were confirmed experimentally.2 Desipramine and protriptyline were measured in atria and ventricles. Increasing infusion rates led to proportional increases in plasma and atrial concentrations. The tissue/medium ratio ranged from 57 to 21 for desipramine and from 43 to 11 for protriptyline according to the time of determination during infusions.3 Heart rate changes, deviation of the electrical axis of the heart and prolongation of atrioventricular conduction were recorded at fixed times during infusion.4 Positive chronotropic effects were noted at plasma concentrations ranging from 0.035 to 0.1 mug/ml for desipramine and from 0.04 to 1.2 mug/ml for protriptyline. At higher plasma concentrations the positive chronotropic effect decreased and bradycardia developed. Both drugs induced right rotation of the electrical axis of the heart. Threshold plasma levels giving 40 degrees rotation were 1.35 mug/ml (desipramine) and 1.75 mug/ml (protriptyline). Atrioventricular conduction was prolonged at threshold plasma concentrations of 2.2 mug/ml for desipramine and 3.6 mug/ml for protriptyline.5 Desipramine is more cardiotoxic than protriptyline. This difference is discussed in relation to the plasma and heart concentration of the two drugs.

Animals

Pharmacokinetic aspects of protriptyline plasma levels.

Plasma levels of protriptyline have been determined in 30 patients undergoing antidepressant therapy. After 3 1/2 weeks treatment at dosage levels of 40 mg/day, protriptyline plasma levels ranged from 430 to 1430 nmol/l. During this period only two-thirds of the subjects had definitely achieved asymptotic concentrations. Single dose studies in 5 volunteers suggest that the volume of distribution of protriptyline shows little intersubject variation. The half life of the drug, however, may vary appreciably from subject to subject, ranging from 54 to 198 h. The effects of two sedatives on mean protriptyline plasma levels have been determined. Mean plasma levels for nitrazepam recipients are indistinguishable from those for patients receiving no night sedation. The mean plasma levels for a group of patients receiving sodium amylobarbitone were significantly reduced. The problems of choice and early adjustment of dosages in order to achieve satisfactory plasma levels is discussed. For practical purposes it is suggested that early values may be of predictive significance in allowing early dosage adjustments to be made.

Administration, Oral

Protriptyline plasma levels and antidepressant response.

Twenty-one depressed outpatients were treated for 4 wk with 20 mg/day of protriptyline. Protriptyline plasma in individuals after 4 wk ranged from 22 ng/ml to 167 ng/ml. There was a negative correlation (-0.50, less than 0.05) between the severity of depression measured by the Hamilton Rating Scale (HRS) and the wk 4 protriptyline concentration. Patients with plasma levels above 70 ng/ml (wk 4) had better outcomes measured by the HRS (p less than 0.05) and the Zung Self-Rating Depression Scale (p less than 0.05) and had greater percent decreases on both scales (p less than 0.05) during treatment than those with lower plasma levels. An upper limit to the therapeutic plasma level range beyond which response to treatment was less satisfactory was not demonstrated in this study.

Adult

The effects of protriptyline and clomipramine in vitro on the uptake of 5-hydroxytryptamine and dopamine in human platelet-rich plasma.

The effects of protriptyline and clomipramine, at concentrations of 10(-7)M to 10(-4)M, were studied in vitro on the uptake of 5-hydroxytryptamine and dopamine uptake in human platelet-rich plasma. It was found that the tertiary amine, clomipramine, was a more potent inhibitor of 5-hydroxytryptamine uptake than the secondary amine, protriptyline. The activity of both compounds was competitive but it was thought unlikely that they acted through tryptamine receptor sites as methysergide 2.5 X 10(-8)M had very little effect on 5-hydroxytryptamine uptake. Neither tricyclic antidepressant had any marked effect on dopamine uptake.

Binding, Competitive

Electrophysiologic studies of perphenazine and protriptyline in a patient with psychotropic drug-induced ventricular fibrillation.

A 51 year old woman sustained ventricular fibrillation while receiving perphenazine and protriptyline. After successful resuscitation and clinical stabilization, cardiac electrophysiologic studies were performed before and after the administration of each of these medications. Perphenazine widened the ventricular echo zone and facilitated induction of short salvoes of ventricular tachycardia (repetitive ventricular response). Protriptyline also widened the ventricular echo zone and allowed easy induction of long runs of ventricular tachycardia. Both psychotropic agents increased the incidence of ventricular dysrhythmias in this patient. The electrophysiologic study is a useful technique in determining the interaction between psychotropic drugs and life-threatening arrhythmias; it may provide a means of identifying the patients with cardiac disease in whom administration of these agents may be fatal.

Major Depressive Disorder

Reversal of chronic diabetes insipidus during treatment with protriptyline.

We have described a 13-year-old white boy with Ondine's curse, sleep apnea and cataplexy who simultaneously developed progressive hypothalamic neuroendocrine deficiencies requiring replacement therapy. The patient was treated with protriptyline, a nonsedating tricyclic antidepressant, for control of the sleep-related symptoms. An unexpected result was the apparent reversal of his chronic diabetes insipidus by protriptyline, necessitating discontinuation of lysine-vasopressin. Some possible mechanisms of action were discussed.

Adolescent

Steady-state protriptyline levels in an outpatient population.

The authors measured steady-state protriptylive levels in 12 outpatients undergoing treatment for depression. The steady-state level of protriptyline was surprisingly high compared with levels obtained when other tricyclic antidepressants were prescribed. This finding probably accounts for the effectiveness of protriptyline at low doses and its frequent side effects.

Administration, Oral

Protriptyline: an effective agent in the treatment of the narcolepsy-cataplexy syndrome and hypersomnia.

The authors present five case reports illustrating that 10-20 mg of protriptyline in a single dose at bedtime can effectively control arousal dysfunction (sleep drunkenness and hypersomnia) and the narcolepsycataplexy syndrome without the apparent development of tolerance and without the side effects that are frequent complications of treatment with other agents. Although protriptyline was efficacious in controlling symptoms, it was found to have relatively poor REM sleep-suppressing properties.

Adult

Sleep apnea: treatment with protriptyline.

Fourteen patients with an average of more than 60 episodes of upper airway obstruction during night sleep were treated with a nonsedating tricyclic antidepressant, protriptyline. Frequency and duration of recorded apneas decreased in 11 cases, and satisfactory control of sleep apnea was maintained with medical therapy alone in 8 of these 11 patients for 7 to 15 months. Potential adverse effects of protriptyline, particularly on the cardiovascular system, limit its use in this illness. These results indicate the possibility of pharmacologic reversal of sleep-induced incoordination of the upper airway.

Adult

Effects of protriptyline and perphenazine in neurotic depressed outpatients.

A four-week comparison of protriptyline 10 mg three times a day and perphenazine 2 mg three times a day, alone and in combination, and a placebo in a group of nonpsychotic depressed outpatients showed no significant differences among any of the treatment groups after both two and four weeks, and a slight trend in favor of the placebo group. A significant positive correlation was observed between changes in hostility and changes in depression, contrary to many commonly held assumptions regarding the relationship between hostility and depression.

Adjustment Disorders

The reversal of clonidine-induced hypotension by protriptyline and desipramine.

The present paper deals with further studies on the interaction between clonidine and tricyclic antidepressants. The pronounced central hypotensive action of 1 mug clonidine/kg, administered into the left vertebral artery of chloralose-anaesthetized cats was readily reversed by protriptyline (300 mug/kg), infused via the same route shortly after the development of the maximum hypotensive effect of clonidine. In earlier studies it has been demonstrated that pretreatment with tricyclic antidepressants significantly diminishes the central hypotensive action of clonidine. This interaction has been presumed to occur at the level of central alpha-adrenoreceptors, where clonidine would be the agonist and tricyclic antidepressants the antagonist. The present findings suggest that a competitive antagonism at the central level, which can occur in either sense, may be involved.

Animals

Plasma concentrations of protriptyline and clinical effects in depressed women.

We studied the relationship between side effects, clinical outcome and the drug plasma levels in 28 female depressed patients treated with protriptyline. After 3 1/2 weeks treatment, patients with plasma levels within a median range (630 to 900 nmol/l) showed better responses to the drug than patients with plasma levels outside this range. There were no statistically signficant correlations between plasma levels and side effect scores or 'corrected' side effect scores (scores after subtracting pretreatment values) for the group at any time after starting the treatment. But we found positive correlations between plasma levels and 'corrected' side effect scores for the neurotic subgroup after 14 and 21 days of treatment. Other correlations between plasma levels and side effect scores were non-significant.

Adjustment Disorders