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Unit Code 81854:
Desipramine, Plasma

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Useful For

Monitoring adequacy of blood concentration during therapy

 

The test may also be useful to evaluate patient compliance.

Clinical Information

Desipramine (Norpramin) is a tricyclic antidepressant; it also is a

metabolite of imipramine. These drugs have also been employed

in the treatment of enuresis in childhood and severe obsessive-

compulsive neurosis. Desipramine is the antidepressant of choice

in patients where maximal stimulation is indicated.

 

Desipramine exhibits 92% bioavailability and is approximately

90% protein bound. As with the other antidepressants, it undergoes

hepatic metabolism and renal elimination with a clearance rate of

30 mL/min/kg. The volume of distribution is 34 L/kg, and the elimination

half-life is 15 to 20 hours.

 

The therapeutic concentration of desipramine is 75 ng/mL to 275 ng/mL.

About 1 to 3 weeks of treatment are required before therapeutic

effectiveness becomes apparent.

 

The most frequent untoward reactions are those attributable to

anticholinergic effects: dry mouth, constipation, dizziness, tachycardia,

palpitations, blurred vision, and urinary retention. These side effects

occur at blood concentrations in excess of 300 ng/mL, although

they may occur at therapeutic concentrations in the early stage of

therapy. Cardiac toxicity (first-degree heart block) is usually associated

with blood concentrations >500 ng/mL.

 

Concurrent administration of phenothiazines (perphenazine displays

the strongest effect) will cause accumulation of the metabolite as the

conversion of desipramine to 10-hydroxydesipramine is blocked.

Dosage adjustments may be in order in this situation. Desipramine

is metabolized by the cytochrome P450 system; all drugs that activate

the P450 system (ie, phenobarbital) will increase the rate of clearance

of desipramine.

Reference Values

Therapeutic concentration:  75-225 ng/mL

Toxic concentration:  >=500 ng/mL

 

Note:    Reference values apply to

                  specimens not obtained from

                  separator tubes.

 

Due to an analytical interference, patients taking

sertraline may have falsely low results and patients

taking clomipramine and amlodipine may have falsely

elevated results.

Interpretation

Desipramine, when administered in doses of 100 mg/day to 200 mg/day

should yield therapeutic levels of 75 ng/mL to 225 ng/mL.

Cautions

This test cannot be performed on whole blood. Plasma must be

separated from cells within 2 hours of drawing.

 

Specimens that are obtained from gel tubes are not acceptable.

Clinical Reference

Ziegler VE, Biggs JT, Rosen SH, et al:  Imipramine and desipramine

plasma levels:  relationship to dosage schedule and sampling

time.  J Clin Psychol 1978;39:660-663

Key