Nortriptyline plasma levels and therapeutic response

Pharmacokinetics of single oral doses of nortriptyline in depressed elderly hospital patients and young healthy volunteers

A single oral dose of 75mg nortriptyline was given to a group of 20 depressed elderly patients in hospital. Subsequent plasma nortriptyline concentrations were used to calculate the half-life and clearance of the drug. These measurements were compared with those made previously in 17 healthy young volunteer subjects. Plasma nortriptyline half-life was longer and clearance slower (p < 0.002) in the elderly group than in the volunteers. There was no correlation of age with either of these parameters within the 2 groups, and no differences in nortriptyline pharmacokinetics could be detected between the male and female volunteer subjects. The possible reasons for these findings and their clinical consequences are discussed.

A double-blind comparison of dothiepin and amitriptyline in patients with primary affective disorder: serum levels and clinical response

In a double-blind parallel group study, thirty-two patients suffering from a primary affective disorder received either dothiepin or amitriptyline. Serum concentrations of total dothiepin plus northiaden or amitriptyline and nortriptyline were estimated. A similar therapeutic response was seen with both drugs but there was no correlation with serum concentrations of amitriptyline or nortriptyline, whereas serum dothiepin correlated positively with clinical response.

Specific radioimmunoassay of amitriptyline and nortriptyline

1 Antisera to nortriptyline were prepared by immunizing rabbits with N-succinylnortriptyline--bovine serum albumin conjugate. 2 A sensitive radioimmunoassay has been developed for the tricyclic antidepressants amitriptyline and nortriptyline. 3 amitriptyline and nortriptyline are separated from each other and from interfering metabolites before assay. 4 Using [3H]-imipramine and [3H]-succinylnortriptyline as tracers the radioimmunoassay can measure amitriptyline and nortriptyline levels down to 2--3 ng/ml using 0.05 ml plasma sample. 5 Agreement between the radioimmunoassay and a gas-chromatographic assay was excellent for both amitriptyline and nortriptyline.

Clinical response and tricyclic plasma levels during treatment with clomipramine

Fifty depressed in-patients at two psychiatric units, one in Italy the other in England, were treated with clomipramine, either orally, or intravenously and orally. A comparison of clinical response with plasma levels of clomipramine and its metabolite, desmethylclomipramine, showed clear relationships especially in the case of desmethylclomipramine. In the intravenously-treated group this was linear, in the orally-treated group it was curvilinear. Plasma levels of desmethylclomipramine and administered clomipramine correlate highly. These findings, together with the fact that significant clinical improvement was observed in only 55% of the patients, suggest that titration of the administered dose to obtain more effective plasma levels of the metabolite might improve the clinical response to the drug in some patients.

Monitoring of antidepressant drug plasma levels: the next ten years

Future studies of the relationship between plasma level and drug response in depressed patients ought to take the following facts into consideration: 1. Selective drug analytical methods must be used and subjected to quality control. Methods for the major urinary metabolite(s) of the parent drug should also be developed. 2. Each drug has individual pharmacokinetic and pharmacodynamic properties--it is unlikely that one drug will be effective in all patients even under optimal kinetic conditions. 3. The pharmacologic and biochemical effects of hitherto investigated tricyclic antidepressants correlate significantly to the concentrations of parent drug and/or its active metabolite in plasma. 4. It is more likely that a significant correlation will be found between the total tricyclic antidepressant level in plasma and the therapeutic outcome in a patient sample if the range of plasma levels is large--in this case the relatively small interindividual differences in plasma protein binding play a minor role. 5. Concomitant somatic disease may change the kinetics of antidepressant drugs. 6. The clinical methods used for selecting and rating study patients with depressive disorders must be standardized. 7. Novel rapidly acting drugs are desirable because the slow onset of action of tricyclic antidepressant seriously hamper their clinical evaluation. 8. A strong correlation between plasma concentration of an antidepressant drug and clinical outcome is strong evidence that the clinical effect is due to the drug rather than nonpharmacological factors.

The role of plasma concentrations in the use of tricyclic antidepressant drugs

1. The range of tricyclic antidepressant plasma levels (or doses) needed for therapeutic response remains largely unresolved, since quantal plasma concentration (or dose)--response relationships have not been clearly defined for either therapeutic or nontherapeutic effects. 2. The fact that certain patients apparently became more depressed at higher plasma levels must be balanced against the facts that "depression" is a mixture of disorders as yet poorly distinguishable and that tricyclic antidepressants have multiple pharmacologic effects. 3. There is presently no justification for routinely monitoring tricyclic antidepressant plasma levels, even though, as for any drug, such determinations are justifiable in patients who are unresponsive or show signs of toxicity. 4. Plasma level determinations can never replace sound clinical judgment and dosage adjustment for individual patients.

Metabolic interaction between amitriptyline and perphenazine in psychiatric patients

1. Steady-state plasma level samples of sixty-five schizophrenic patients from two psychiatric hospitals assigned to three treatment groups (amitriptyline 150 mg/day, perphenazine 20 mg/day and a combination of amitriptyline and perphenazine at 150 mg and 20 mg/day) were assayed for amitriptyline (AT), endogenous nortriptyline (NT) and perphenazine (PPZ) using gas-liquid chromatography. 2. Results reveal that AT and NT levels are independent of sex and hospital environment. 3. PPZ significantly increased the steady-state NT plasma levels, probably through inhibition of the hydroxylation biotransformation pathway, but had no effect on AT levels, thus indicating that PPZ has no influence on the desmethylation pathway, or alternatively, the hydroxylation of AT.

Clinical response and plasma concentration of amitriptyline and its metabolite nortriptyline

Plasma levels of amitriptyline and nortriptyline were measured twice weekly in 62 patients treated for three weeks with i.m. amitriptyline 120 mg/day. In half the patients the ratio of amitriptyline to nortriptyline was under 1 and in the other half it was greater than 1. 30 of these 62 patients were clinically monitored with the Hamilton Rating Scale and the side effects of the drug were recorded. There was no correlation between plasma level of the drug and its side effects, but there was a statistically significant curvilinear correlation between the plasma levels of amitriptyline plus nortriptyline and nortriptyline alone, and the clinical effect. The practical value of this type of investigation was demonstrated by showing that patients whose drug plasma level was not in the therapeutic range, were clinically improved after adjustment of the dose. The plasma level of amitriptyline plus nortriptyline must lie between 60 to 220 ng/ml, and that of nortriptyline between 60 to 140 ng/ml, to obtain the best clinical effect. Associated treatments, age, weight and sex of patients, and the type of depression did not appear significantly to affect the plasma level of the drug.

Ion-pair liquid chromatography of amitriptyline and metabolites in plasma

A method is described for the determination of amitriptyline and nortriptyline in the plasma of patients during treatment. The method is based on liquid chromatography of the amines as ion-pairs with perchlorate. The separation column is packed with silica gel, and a mixture of diisopropyl ether, dichloromethane, methanol and water containing the counter ion is used as eluent. High efficacy and stability of the system is achieved. The separation of metabolites is demonstrated. The cis- and trans-10-hydroxy isomers of amitriptyline and nortriptyline are easily resolved with this chromatographic system.

The practical significance of nortriptyline plasma control. A prospective evaluation under routine conditions in endogenous depression

The problem of the advantage of using nortriptyline (NT) plasma level during treatment for endogenous depression has been approached. In an ordinary psychiatric department, 34 patients had their NT level checked the second week of treatment and their dosage subsequently adjusted, if it was outside the recommended therapeutic plasma range (50--150 ng/ml). A cautious dose policy led to low plasma levels followed by dose increase in about 40% of the patients. Only in a few patients was the plasma level above the upper limit. The general outcome, about 20% failures, was compatible with the best in literature. These and other results suggest that controlling the NT plasma concentration, aiming at a level of around 100 ng/ml, might offer a therapeutic advantage, but only if the department has established a therapeutic strategy that involves such a monitoring system. The therapeutic outcome was the same as or even better in the old-age group than that in patients under 65 years of age.

Cardiac effects of tricyclic antidepressant medication. A preliminary study of nortriptyline

Systolic time intervals and drug plasma concentrations have been measured in a group of patients receiving repeated treatment with nortriptyline. Significant positive correlations between plasma nortriptyline levels and prolongation of pre-ejection phase (P less than 0.005)) and increase in the ratio pre-ejection phase, left ventricular ejection time (P less than 0.05) were obtained. A deterioration in cardiac function, with increase in heart rate, resulting in a negative inotropic effect has been shown to occur with therapeutic doses of nortriptyline. The potential dangers of tricyclic antidepressant drugs on the heart in patients whose myocardium is already compromised or those who accumulate high plasma concentrations are emphasised.

Intrapatient variability of serial steady-state plasma tricyclic antidepressant concentrations

Nine or 10 serial steady-state plasma measurements of amitryptyline, desipramine, desmethyldoxepin, doxepin, imipramine, nortriptyline, or protriptyline were made in 23 depressed patients. Each patient was monitored for compliance by pill counts, and sampling time was controlled carefully to determine intrapatient variability of steady-state tricyclic levels on a day-to-day basis. The coefficients of variation during serial sampling of the various ingested drugs were: amitriptyline, 21%; desipramine, 26%; doxepin, 21%; imipramine, 14%; nortriptyline, 13%; and protriptyline, 17%. The therapeutic ranges for the tricyclic antidepressants are relatively wide, so coefficients of variation of these magnitudes indicate that the position of an individual patient in relation to the optimal therapeutic range can be reliably determined on a clinical basis.

A new antidepressant butriptyline: plasma levels and clinical response

Ten patients who suffered from a primary depressive illness were treated with a new antidepressant drug butriptyline (150 mg/day). Six of the patients showed marked clinical improvement, as judged by depression rating scores, at the end of 22 days of treatment. No simple relationship was found between clinical response and plasma butriptyline concentration. Butriptyline is an effective antidepressant agent, well tolerated and with few side effects.