Electrocardiogram changes and therapeutic desipramine and 2-hydroxy-desipramine concentrations in elderly depressives

Geriatric Depression

Depression in the elderly is more common than once thought, especially in nursing home settings, where as many as 25% of residents can exhibit signs and symptoms of depression. Depression in the elderly can have a significant impact on overall health and desired outcome. The depressed elderly patient has been shown to have worsened prognosis of concomitant medical conditions, increased use of health care, decreased recovery time, and more likelihood to experience accelerated physical deterioration. Suicide represents the most serious complication of depression of the older depressed individual. The elderly are at a disproportionate risk for suicide attempts and are more likely to be successful. Diagnosis should be made using Diagnostic and Statistical Manual of Mental Disorders(4th ed.) (DSMIV) criteria, and clinicians should use standardized rating scales such as the Geriatric Depression Scale to assist in monitoring the severity of depressive symptoms and the efficacy of antidepressant treatment. Several treatment options are available to the clinician and include psychotherapy, electroconvulsive therapy, older antidepressants such as the tricyclics, and newer more tolerable therapies such as the serotonin reuptake inhibitors. Drug therapy should be individualized and should take into account the pharmacokinetic and pharmacodynamic changes that are associated with normal aging.

Aging and Clinical Pharmacology: Implications for Antidepressants

The elderly frequently have changes in pharmacokinetics, sensitivity to medications, homeostatic reserve (ability to tolerate physiological challenges), exposure to multiple medications, and adherence. All of these age-associated factors can potentially influence total exposure to medication, adverse effects, and subsequent treatment outcome. Most clinical trials are performed with healthy, younger adults. Extrapolating the results of these trials to the elderly may be inappropriate, particularly for the antidepressant treatment of depression. The authors review these age-associated differences and discuss their implications for antidepressant use in older adults.

Metabolism of tricyclic antidepressants

1. Despite the considerable advances in the treatments available for mood disorders over the past generation, tricyclic antidepressants (TCAs) remain an important option for the pharmacotherapy of depression. 2. The pharmacokinetics of TCAs are characterized by substantial presystemic first-pass metabolism, a large volume of distribution, extensive protein binding, and an elimination half-life averaging about 1 day (up to 3 days for protriptyline). 3. Clearance of tricyclics is dependent primarily on hepatic cytochrome P450 (CYP) oxidative enzymes. Although the activities of some P450 isoenzymes are largely under genetic control, they may be influenced by external factors, such as the concomitant use of other medications or substances. Patient variables, such as ethnicity and age, also affect TCA metabolism. The impact of gender and related reproductive issues is coming under increased scrutiny. 4. Metabolism of TCAs, especially their hydroxylation, results in the formation of active metabolites, which contribute to both the therapeutic and the adverse effects of these compounds. 5. Renal clearance of the polar metabolites of TCAs is reduced by normal aging, accounting for much of the increased risk of toxicity in older patients. 6. Knowledge of factors affecting the metabolism of TCAs can further the development and understanding of newer antidepressant medications.

Effects of carbamazepine coadministration on plasma concentrations of trazodone and its active metabolite, m-chlorophenylpiperazine

Effects of carbamazepine coadministration on plasma concentrations of trazodone and its active metabolite, m-chlorophenylpiperazine (m-CPP) were studied in six depressed patients treated with trazodone. The daily dose of trazodone was 150 mg in three cases and 300 mg in three cases. Carbamazepine, 400 mg/day, was coadministered for 4 weeks, and blood samples were taken before carbamazepine addition and at weekly intervals after the addition. Carbamazepine significantly (p < 0.01) decreased plasma concentrations of not only trazodone but also m-CPP at each week. On the average, plasma concentrations of trazodone and m-CPP at 4 weeks were 24 and 40% of the corresponding precarbamazepine values. This study thus suggests that carbamazepine coadministration decreases plasma concentrations of trazodone and m-CPP by inducing the metabolism of these compounds.

Cardiovascular effects of fluvoxamine and maprotiline in depressed patients

In the choice of an antidepressant drug the clinician must often consider the presence of a cardiovascular comorbidity in depressed patients. In the present study the cardiovascular effects of fluvoxamine and maprotiline were compared in a double-blind trial in which the quantitative changes in ECGs were assessed before and during a 3-week treatment. A total of 33 patients (mean age 44 years; range 20-65 years) with major depressive disorder (RDC) who were free from clinically relevant organic diseases were investigated. After a 7-day wash-out period, a 3 week treatment phase was started with 200 mg daily of either fluvoxamine (n = 18) or maprotiline (n = 15). On days 0, 7, 14 and 21 a 12-lead standard ECG was performed and the drug plasma levels were determined. All ECGs were analysed in a blind fashion by an internist. Maprotiline caused a significant prolongation of the PR interval (P < 0.001) and of the QRS interval (P < 0.01) was well as an increase in heart rate (P < 0.001). The QTc interval was only tendentially prolonged (P < 0.10) and the P-wave duration and T-wave amplitude were not affected by maprotiline. No significant changes in ECG parameters were observed during treatment with fluvoxamine; and there was a nonsignificant trend (P < 0.10) for a lower heart rate during treatment. Blood pressure was not affected by treatment with either antidepressant. In both groups no significant correlations were found between ECG findings and the plasma levels of the drugs. Our results confirm that fluvoxamine in therapeutic dose causes no alteration in surface ECG regarding cardiac conduction and repolarization. Conversely, maprotiline caused a significant prolongation of atrioventricular and intraventricular conduction and a rise in heart rate. Although these effects were not clinically relevant in our sample of patients without overt heart disease, they should be taken into account when treating depressed patients with concomitant cardiac disease.

Electrocardiographic effects of desipramine and 2-hydroxydesipramine in children, adolescents, and adults treated with desipramine

OBJECTIVE

To assess the developmental effects of desipramine (DMI) treatment on the electrocardiogram (ECG), we investigated serum concentrations of DMI ([DMI]), and its major active metabolite 2-hydroxydesipramine ([OHDMI]) and ECG parameters.

METHODS

ECGs and [DMI] and [OHDMI] were analyzed from 50 children, 39 adolescents, and 30 adult psychiatric patients receiving DMI.

RESULTS

There were modest overall correlations between [DMI], [OHDMI], or [OHDMI+DMI], and the PR and QRS intervals when data from all 119 subjects were pooled. Within the pediatric age groups there were no significant associations between serum drug levels and heart rate or conduction intervals; and in all subjects with ECG abnormalities, there were some findings of higher [DMI], [OHDMI], and [OHDMI+DMI].

CONCLUSIONS

These findings indicate that only modest associations of [DMI] and [OHDMI] with ECG conduction intervals were found, and are not likely to be clinically significant in any of the age groups studied. Compared with adults, children and adolescents do not appear to be at increased risks for ECG changes related to DMI treatment or to circulating concentrations of [DMI] or [OHDMI].

Developmental changes in serum concentrations of desipramine and 2-hydroxydesipramine during treatment with desipramine

Steady-state serum concentrations of desipramine (DMI) and its metabolite, 2-hydroxydesipramine (OHDMI), were measured in 40 children, 36 adolescents, and 27 adult psychiatric patients. The authors predicted that younger patients would show more efficient elimination of DMI, with greater amounts of OHDMI. OHDMI averaged 52% lower than DMI. DMI per weight-corrected dose (ng/mL: mg/kg) rose significantly with maturation, from 50 in children and 56 in adolescents to 91 in adults. Contrary to expectation, OHDMI per DMI dose also rose with age, from 17 in children and 20 in adolescents to 26 in adults. It was concluded that: (1) similar mg/kg doses of DMI result in lower DMI and OHDMI in children; (2) children metabolize both DMI and OHDMI more rapidly than adults; and (3) children do not have high circulating concentrations of OHDMI.

Imipramine and 2-hydroxyimipramine: comparative cardiotoxicity and pharmacokinetics in swine

The hemodynamic, cardiographic, and initial pharmacokinetic characteristics of the de novo administration of the 2-hydroxymetabolite (2-OH-IMI) of imipramine (IMI), compared with its parent was studied in a swine preparation. Cardiac output, arterial pressure, and the continuous electrocardiogram were assessed after the intravenous administration of the drug or its metabolite. Plasma, sampled over 120 min and CSF sampled at 60 min were analyzed by reverse phase HPLC with spectroflurometric detection. Equilibrium dialyses were performed on plasma sampled at 60 min. 2-OH-IMI, in doses of 5-6 mg/kg, compared to dosages of IMI up to 8.5 mg/kg, produced a significantly greater incidence of life-threatening arrhythmias, and caused profound and significant decreases in blood pressure and cardiac output. 2-OH-IMI had a smaller volume of distribution (Vd) and shorter half-life. CNS penetration, as estimated by CSF/plasma ratios, was significantly greater for 2-OH-IMI. These phenomena were partly accounted for by significantly less protein binding for the hydroxymetabolite. It is concluded that 2-OH-IMI has increased penetrance into the CNS despite a smaller Vd and that it is significantly more cardiotoxic than its parent.

Determination of imipramine, desipramine and their hydroxy metabolites by reversed-phase chromatography with ultraviolet and coulometric detection

A reversed-phase high-performance liquid chromatographic method is described which analyzes imipramine, desipramine and their corresponding 2-hydroxy metabolites with sequential ultraviolet and coulometric detection from a single common extraction step, so that a wider dynamic range of plasma concentrations can be measured requiring smaller sample volumes. Applicability is broader including single-dose pharmacokinetic studies as well as steady-state concentrations. The extraction procedure gives excellent recoveries for imipramine, desipramine and their metabolites (mean +/- S.D.): ultraviolet detection, imipramine 99.5 +/- 0.68%, desipramine 100 +/- 0.0%, 2-hydroxyimipramine 97.8 +/- 3.5% and 2-hydroxydesipramine 93.1 +/- 4.22%; coulometric detection, imipramine 97.5 +/- 1.9%, desipramine 98.3 +/- 1.2%, 2-hydroxyimipramine 90.3 +/- 4.0% and 2-hydroxydesipramine 86.6 +/- 7.5%.

Sudden death in children receiving Norpramin: a review of three reported cases and commentary

The 1990 "package insert" for Norpramin, the Merrell Dow Pharmaceuticals Inc., brand of desipramine, was changed to include the following statement in the Adverse Reactions section, "There has been a report of an 'acute collapse' and 'sudden death' in an eight-year-old (18 kg) male, treated for two years for hyperactivity. There have been additional reports of sudden death in children." The purpose of this commentary is to review what is known about the three reported cases of sudden death and to discuss the implications of these tragedies for children receiving treatment with tricyclic drugs.

The electrocardiographic manifestations of cyclic antidepressant therapy and overdose: a review

Cyclic antidepressants may cause changes in the electrocardiogram at therapeutic or toxic serum levels. The most serious complications of cyclic antidepressant toxicity are dysrhythmias, hypotension, and seizures. It is predominantly the cardiotoxic effects that cause mortality. Once cardiotoxicity is evident, the treatment of choice is serum alkalinization, preferably by sodium bicarbonate therapy. In order to predict which overdose patients are at high risk for complications, electrocardiographic criteria have been identified as reliable screens. For "first generation" tricyclic antidepressants, QRS prolongation (particularly greater than 100 msec) and a terminal 40-ms frontal plane axis greater than 120 degrees are the most sensitive. This article reviews antidepressant pharmacology, electrocardiographic manifestations of antidepressant cardiotoxicity, and approaches to treatment of antidepressant-induced conduction disturbances and dysrhythmias.

The pharmacokinetics of tricyclic antidepressant drugs in the elderly

Antidepressants, especially tricyclic agents (TCAs), are increasingly used in geriatric patients since depression is a common mood disorder in the elderly and the size of elderly population is increasing. Notwithstanding the importance of kinetics to better use of drugs, its study in the elderly (regarding TCAs) is not sufficiently developed. The present paper briefly reviews the available data on amitriptyline, nortriptyline, protriptyline, imipramine, desipramine and clomipramine kinetics in the elderly.

Tricyclic antidepressants: contemporary issues for therapeutic practice

The clinical pharmacology of tricyclic antidepressants is reviewed, with an emphasis on recent findings. These medications have become the treatment of choice for the majority of depressed patients. Their efficacy is limited by lack of vigor and precision in dosage. Pharmacokinetic aspects are addressed which affect the rationale for selective use and interpretation of plasma concentration monitoring. These include nonlinearity, active metabolites, plasma protein binding and age effects. Specific indications for therapeutic drug monitoring occur with patients who fail to respond, those at risk because of age, medical condition or polypharmacy, and to check compliance. Integration of knowledge concerning pharmacokinetics and plasma levels with clinical response will aid in making appropriate pharmacotherapeutic decisions.

Unsolved problems in the pharmacotherapy of depression

Five unsolved problems in the pharmacotherapy of depression are discussed: (a) it is not possible to differentiate endogenous and nonendogenous depression; (b) a selective efficacy of serotonin and noradrenaline reuptake inhibitors cannot be demonstrated; (c) the relationship between plasma levels and antidepressant effect is still unclear: plasma levels are influenced by pharmacogenetic factors, age, route of application, and concomitant treatment with other drugs; (d) evidence is growing for the development of tolerance towards therapeutic effects of antidepressants; (e) no pretreatment variable allows prediction of treatment response: the best predictor is the initial response to treatment.