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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

Effects of protriptyline on diurnal and nocturnal oxygenation in patients with chronic obstructive pulmonary disease.

OBJECTIVE: To determine the effects of a nonsedating tricyclic antidepressant (protriptyline) on pulmonary function (lung volume, expiratory flow), arterial blood gases, sleep architecture, and sleep-induced breathing abnormalities in patients with chronic obstructive pulmonary disease. DESIGN: A before-and-after trial in which patients, blinded to treatment, were given a placebo for 2 weeks, followed by 2 and 10 weeks of protriptyline treatment. SETTING: Referral-based pulmonology clinic in a public institution. PATIENTS: Sixteen outpatients were enrolled in the trial. Complete results for 11 patients and partial results for 3 patients are presented. INTERVENTIONS: Patients were evaluated at baseline, after receiving placebo for 2 weeks, and after 2 and 10 weeks of protriptyline therapy (20 mg/d, taken at bedtime). MEASUREMENTS AND MAIN RESULTS: At baseline, for the whole group, forced expiratory volume in 1 second (FEV1) was 1.0 +/- 0.08 L (mean +/- SE); the partial pressure of O2 in arterial blood (PaO2) was 59 +/- 1.2 mm Hg; and the partial pressure of CO2 in arterial blood (PaCO2) was 48.9 +/- 1.2 mm Hg. These variables remained stable after placebo. Pulmonary function test results were unchanged with protriptyline therapy. Arterial blood gas levels improved with such therapy: PaO2 levels increased by 5.1 +/- 1.4 mm Hg after 2 weeks and 6.7 +/- 2.4 mm Hg after 10 weeks (P less than 0.01); PaCO2 levels decreased by 4.2 +/- 0.9 mm Hg after 2 weeks and 2.2 +/- 1.1 mm Hg after 10 weeks (P less than 0.01). Total sleep times were similar at these visits. The only change in sleep architecture was a significant decrease in rapid eye movement (REM) sleep. The lowest value for the saturation of hemoglobin with O2 in arterial blood (SaO2) seen during sleep was 72.0% +/- 2.0% at baseline. After 2 and 10 weeks of protriptyline therapy, SaO2 values increased by 7.1% +/- 1.6% and 5.0% +/- 2.1%, respectively (P less than 0.01). With protriptyline therapy, the cumulative SaO2 curve, derived from data obtained during sleep, shifted down and to the right. CONCLUSIONS: Protriptyline improves diurnal and nocturnal hypoxemia in patients with chronic obstructive pulmonary disease. These changes are not related to changes in pulmonary mechanics.

Circadian Rhythm

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

Changes in day and night time oxygenation with protriptyline in patients with chronic obstructive lung disease.

The effect of protriptyline, a tricyclic antidepressant, on sleep architecture, nocturnal arterial oxygen desaturation, pulmonary function, and diurnal arterial blood gases was investigated in an open study of 14 patients with stable chronic obstructive lung disease. Daytime and overnight measurements were made before and 2 and 10 weeks after they started protriptyline (20 mg daily at bedtime). Two patients had to be excluded before the second visit and one before the third visit because of changes in treatment for their chest disease. Protriptyline caused mouth dryness in all patients and dysuria in six men. With protriptyline there were no significant changes in total sleep time, sleep period time, or the percentages of total sleep time occupied by stage I-II and stage III-IV sleep. The mean (SEM) percentage of total sleep time spent in rapid eye movement (REM) sleep decreased from 11.1 (1.7) to 4.6 (0.7) at two weeks and to 4.2 (1.0) at 10 weeks. After protriptyline the time spent during sleep with an arterial oxygen saturation (SaO2) below each 5% increment above 65% was less than the baseline time; the lowest SaO2 (%) reached during sleep increased from 64.5 (1.7) to 72.7 (2.1) at 2 weeks and to 77.4 (2.1) at 10 weeks. Lung volumes and expiratory flows were unchanged during the study. Daytime arterial oxygen tension (PaO2) increased from 57 (1.4) mm Hg before treatment to 62 (1.9) mm Hg at 2 weeks and to 66 (1.9) mm Hg at 10 weeks (7.6 (0.2), 8.3 (0.3), 8.8 (0.3) kPa). Carbon dioxide tension fell from 52 (2.3) mm Hg to 49 (1.4) mm Hg at 2 weeks and to 48 (2.0) mm Hg at 10 weeks (6.9 (0.3), 6.5 (0.2), 6.4 (0.3) kPa), but these changes were not significant. These results suggest that protriptyline may benefit patients with chronic obstructive lung disease by reducing the sleep induced falls in SaO2 and improving diurnal PaO2; a controlled trial is now required.

Aged

Response of obstructive sleep apnea to fluoxetine and protriptyline.

Protripyline is the pharmacologic agent most commonly used to treat obstructive sleep apnea (OSA); however, its anticholinergic side effects make it intolerable to many patients. Because serotonin may be a central respiratory stimulant and because the serotonin-uptake inhibitor, fluoxetine, is usually well tolerated, we wanted to try fluoxetine in the treatment of OSA. Therefore, we compared the effect of fluoxetine to that of protriptyline in 12 patients with OSA. Both drugs significantly decreased the proportion of REM sleep time and decreased the number of apneas or hypopneas in NREM sleep. The response to fluoxetine was equivalent to that of protriptyline; however, for the group as a whole, there was no significant improvement in the number of arterial oxygen desaturation events, the level of arterial oxygen desaturation, or the number of arousals with either agent. Although there was wide variability in the response to each medication, six of the 12 patients had good responses, including improvement in oxygenation, to either fluoxetine or protriptyline. Three patients could not complete the trial of protriptyline. We conclude that fluoxetine is beneficial to some, but not all, patients with OSA. Fluoxetine was better tolerated than protriptyline.

Adult

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 use of protriptyline for respiratory failure in patients with chronic airflow limitation.

Treatment of nocturnal hypoventilation in patients with restrictive chest wall disease and respiratory failure, results in improved daytime arterial blood gas tensions, increase in functional ability and longer survival. Success has been achieved with the use of protriptyline which reduces the duration of rapid eye movement (REM) sleep during which nocturnal hypoventilation occurs. Eighteen patients with severe chronic airflow limitation (CAL), took part in a randomized, double-blind, crossover trial of protriptyline and placebo. Seventeen patients completed the study. The use of protriptyline was associated with a fall in the median percentage of total sleep time spent in REM from 16 to 8.8% (p less than 0.01). This was associated with a reduction in the median daytime arterial carbon dioxide tension from 6.4 kPa (range 5.2-8.5 kPa) to 5.8 kPa (range 5.0-8.1 kPa) (p less than 0.01); increased respiratory muscle strength (p less than 0.05), and increased six minute walking distance from a median of 258 m (range 58.5-585 m) to 275 m (range 171-598 m) (p less than 0.02). We found pharmacological treatment of REM-related nocturnal hypoventilation in patients with CAL to be effective, but anticholinergic side-effects, particularly in older male patients, might preclude long-term treatment.

Adult

Effect of protriptyline on ventilatory responses to hypercapnia and asphyxia in normal subjects.

A double-blind crossover study was undertaken to assess the effect of protriptyline on ventilatory responses in normal subjects. Seven subjects received in random order placebo, 10 mg and 20 mg protriptyline daily for 2 weeks. Measurements of hypercapnic ventilatory response (HCVR) and asphyxial hypoxic ventilatory response (HVR) were made before treatment, 6-8 h after the first dose, and after 2 weeks treatment. Mean HCVR and HVR following 10 mg and 20 mg protriptyline did not differ significantly from measurements on placebo, neither for the single dose study or after 2 weeks.

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