Do urinary MHPG and plasma drug levels correlate with response to amitriptyline therapy?

Does 24-h urinary MHPG predict treatment response to antidepressants? I. A review

The ability of pretreatment 3-methoxy-4-hydroxyphenylglycol (MHPG) to predict response to various antidepressants is reviewed. MHPG appears to be a modest predictor of treatment response to imipramine but does not appear to be a reliable predictor for other antidepressants.

Urinary MHPG, platelet 3H-imipramine binding and symptomatology in depression: an exploratory study of clinical heterogeneity

Urinary MHPG concentrations and platelet 3H-imipramine binding (Bmax, Kd) were measured in 20 psychiatric inpatients with diagnoses of major depressive disorder. Clinical assessments were performed using the Present State Examination (PSE) interview, and several dimensions of symptomatology were constructed on the basis of the PSE items. There was a significant positive relationship between Bmax and items reflecting both psychomotor retardation and anxiety. Urinary MHPG bore a comparatively complex nonlinear relationship to Bmax and to the psychomotor retardation symptom dimension. Urinary MHPG also showed an inverse, curvilinear correlation with certain neurotic symptoms. The implications of these findings are briefly discussed in the light of the "dysregulation" hypothesis of affective disorder.

Amitriptyline and oxaprotiline in the treatment of hospitalized depressive patients. Clinical aspects, psychophysiology, and drug plasma levels

Amitriptyline (AT) and the noradrenaline reuptake inhibiting antidepressant oxaprotiline (OT = hydroxymaprotiline) were compared in 59 primary depressive inpatients in a 4-week double blind parallel group design. In the Hamilton Depression Rating Scale and 2 self-rating scales AT proved to be more efficient than OT, mainly with respect to disturbances of appetite and sleep. Agitated patients receiving OT needed more additional tranquilizing medication. The number of side-effects did not differ. Both drugs increased heart rate and skin resistance level (SRL) to about the same degree and did not influence the number of spontaneous fluctuations of SRL, habituation of SRL orienting responses (OR), frequencies of respiration and blinking. Salivation was temporarily more impaired by AT. All physiological variables differed between patients and 30 healthy controls during the whole 4-week trial. Clinical outcome showed a linear relation to OT plasma levels. For AT a therapeutic window was confirmed for concentrations of AT and its metabolite nortriptyline between 125 and 200 ng/ml. Patients whose SRL-OR habituated rapidly had a better outcome than slow habituators. Urinary excretion of 3-methoxy-4-hydroxyphenylglycol was lower in patients than in controls but could not predict outcome with either drug.

Opposite effects of chronic imipramine treatment on brain and urine MHPG levels in the rat

Acute imipramine (IMI; 20 mg/kg, ip) in rats decreased the brain concentration of 3-methoxy-4-hydroxyphenethylene glycol (MHPG), a metabolite of norepinephrine (NE), to 85% of control 24 hr after injection. In contrast, chronic IMI (20 mg/kg, ip, daily for 14 days) significantly raised brain MHPG levels to 123% of control, while reducing brain NE levels. Urinary MHPG levels were reduced by both acute and chronic IMI treatments, to 52% and 51%, respectively. These data suggest that the brain turnover of NE is reduced after acute IMI, but is elevated after chronic treatment. Although urinary levels of MHPG changed in parallel with brain levels following an acute administration of IMI, such was not the case after chronic administration. We conclude that caution must be used in extrapolating drug-induced changes in urinary metabolite levels to brain amine function.

MHPG excretion in endogenous depression: relationship to clinical state and the effects of ECT

In a group of 70 patients with endogenous depression entering a controlled trial of real versus sham ECT, urinary 3-methoxy-4-hydroxyphenylglycol (MHPG) excretion was significantly reduced by comparison with previously studied groups of control subjects, of acute and chronic schizophrenic patients and of anxious patients. However, urinary MHPG was unrelated to severity of depression, or to the presence of delusions, retardation or agitation. MHPG excretion did not predict clinical outcome, or the response to ECT. Urinary MHPG content at trial entry was unrelated to past tricyclic antidepressant or benzodiazepine medication, although an influence of the latter on the findings cannot be excluded, since all patients received benzodiazepine (nitrazepam) night sedation during the trial. During the 4-week trial MHPG excretion remained low and did not increase in relation to change in clinical state, although there was a small but significant increase in patients who received real ECT. The findings confirm that urinary MHPG excretion is reduced in depression, but establish that such reductions are not state dependent. Since the increase in MHPG excretion with ECT is not related to changes in clinical state, the former presumably does not reflect the mechanism of action of ECT.

Monoamine metabolites as predictors of antidepressant response: a critique

Monoamine metabolite measurements are being increasingly used for making nosological, symptomatological and pharmacological profiles of the affective disorders. A number of unresolved methodological issues question the validity of using baseline metabolite levels for predicting treatment response. Some studies show correlations between baseline metabolite levels and response to treatment with specific antidepressant agents. Effects of antidepressant treatment on metabolite levels may be useful in predicting drug response.

Antidepressive effect and pharmacokinetics of amitriptyline with consideration of unbound drug and 10-hydroxynortriptyline plasma levels

In 27 inpatients with primary affective disorder the urinary excretion of 3-methoxy-4-hydroxyphenylglycol (MHPG) was measured prior to a 4-week treatment with 150 mg amitriptyline (AT)/day. Ratings according to the Hamilton depression scale were performed before therapy and repeated after 2 and 4 weeks. Plasma levels of AT, nortriptyline (NT), and E-10-hydroxynortriptyline (OHNT) were assayed weekly, and binding of AT to plasma proteins was determined in one sample. Better therapeutic results were obtained at intermediate, as compared to low and high concentrations of AT or AT plus NT. Independent evaluation of AT and metabolite levels revealed that patients with AT of 50--125 ng/ml responded particularly well when NT did not exceed 95 ng/ml or when NT plus OHNT was below 150 ng/ml. Outside this "therapeutic window' the outcome was markedly poorer. Interindividual variation of AT binding was much smaller than variation of total concentrations. Evaluation of free, instead of total levels did not help to clarify the relationship between clinical and pharmacokinetic variables. Plasma levels within the optimal ranges were found in more patients with high than with low MHPG excretion. The free fraction of OHNT in plasma of healthy subjects was about 35%.