DESIPRAMINE

Absorption

Desipramine hydrochloride is rapidly and almost completely absorbed from the gastrointestinal tract. It undergoes extensive first-pass metabolism. Peak plasma concentrations are attained 4 - 6 hours following oral administration.

Toxicity

Male mice: LD50 = 290 mg/kg, female rats: LD50 = 320 mg/kg. Antagonism of the histamine H1 and α1 receptors can lead to sedation and hypotension. Antimuscarinic activity confers anticholinergic side effects such as blurred vision, dry mouth, constipation and urine retention may occur. Cardiotoxicity may occur with high doses of desipramine. Cardiovascular side effects in postural hypotension, tachycardia, hypertension, ECG changes and congestive heart failure. Psychotoxic effects include impaired memory and delirium. Induction of hypomanic or manic episodes may occur in patients with a history of bipolar disorder. Withdrawal symptoms include GI disturbances (e.g. nausea, vomiting, abdominal pain, diarrhea), anxiety, insomnia, nervousness, headache and malaise.

Originator

Pertofran,Geigy,UK,1963

The Uses of DESIPRAMINE

Desipramine is used for depression of various etiology and in particular for endogenous depression.

The Uses of DESIPRAMINE

Antidepressant.

Background

Desipramine hydrochloride is a dibenzazepine-derivative tricyclic antidepressant (TCA). TCAs are structurally similar to phenothiazines. They contain a tricyclic ring system with an alkyl amine substituent on the central ring. In non-depressed individuals, desipramine does not affect mood or arousal, but may cause sedation. In depressed individuals, desipramine exerts a positive effect on mood. TCAs are potent inhibitors of serotonin and norepinephrine reuptake. Secondary amine TCAs, such as desipramine and nortriptyline, are more potent inhibitors of norepinephrine reuptake than tertiary amine TCAs, such as amitriptyline and doxepine. TCAs also down-regulate cerebral cortical β-adrenergic receptors and sensitize post-synaptic serotonergic receptors with chronic use. The antidepressant effects of TCAs are thought to be due to an overall increase in serotonergic neurotransmission. TCAs also block histamine-H1 receptors, α1-adrenergic receptors and muscarinic receptors, which accounts for their sedative, hypotensive and anticholinergic effects (e.g. blurred vision, dry mouth, constipation, urinary retention), respectively. See toxicity section below for a complete listing of side effects. Desipramine exerts less anticholinergic and sedative side effects compared to tertiary amine TCAs, such as amitriptyline and clomipramine. Desipramine may be used to treat depression, neuropathic pain (unlabeled use), agitation and insomnia (unlabeled use) and attention-deficit hyperactivity disorder (unlabeled use).

Indications

For relief of symptoms in various depressive syndromes, especially endogenous depression. It has also been used to manage chronic peripheral neuropathic pain, as a second line agent for the management of anxiety disorders (e.g. panic disorder, generalized anxiety disorder), and as a second or third line agent in the ADHD management.

Definition

ChEBI: A dibenzoazepine consisting of 10,11-dihydro-5H-dibenzo[b,f]azepine substituted on nitrogen with a 3-(methylamino)propyl group.

Manufacturing Process

Oxidative coupling of o-nitrotoluene gives 4,4'-dinitrodibenzyl which is reduced with hydrogen to the diamine. The diamine is pyrolyzed to give dihydrobenzazepine. This is reacted with N-(3-chloropropyl)-Nmethylbenzamine to give N-benzyldesipramine. This is debenzylated by reductive cleavage and then reacted with HCl.

brand name

Norpramin (Sanofi Aventis); Pertofrane (Sanofi Aventis).

Therapeutic Function

Psychostimulant

Mechanism of action

Its antidepressant effect results from increases in the level of NE in CNS synapses, and long-term administration causes a downregulation of α1-adrenoceptors and desensitization of presynaptic α2-receptors, equilibrating the noradrenergic system and, thus, correcting the dysregulated output of depressed patients. The SSRIs do not produce this effect. Desipramine also downregulates the NET, but not the 5-SERT . Substantial loss of NE transporter–binding sites takes 15 days to occur and is accompanied by a marked reduction of NET function in vivo. Desipramine has weak effects on 5-HT reuptake.

Pharmacokinetics

Desipramine, a secondary amine tricyclic antidepressant, is structurally related to both the skeletal muscle relaxant cyclobenzaprine and the thioxanthene antipsychotics such as thiothixene. It is the active metabolite of imipramine, a tertiary amine TCA. The acute effects of desipramine include inhibition of noradrenaline re-uptake at noradrenergic nerve endings and inhibition of serotonin (5-hydroxy tryptamine, 5HT) re-uptake at the serotoninergic nerve endings in the central nervous system. Desipramine exhibits greater noradrenergic re-uptake inhibition compared to the tertiary amine TCA imipramine. In addition to inhibiting neurotransmitter re-uptake, desipramine down-regulates beta-adrenergic receptors in the cerebral cortex and sensitizes serotonergic receptors with chronic use. The overall effect is increased serotonergic transmission. Antidepressant effects are typically observed 2 - 4 weeks following the onset of therapy though some patients may require up to 8 weeks of therapy prior to symptom improvement. Patients experiencing more severe depressive episodes may respond quicker than those with mild depressive symptoms.

Synthesis

Desipramine, 10,11-dihydro-5-[3-(methylamino)propyl]-5H-dibenz[b,f] azepine (7.1.13), differs from imipramine in that it contains only one methyl group on the nitrogen atom of the propylamine side chain. The suggested methods of desipramine synthesis are very simple, and the difference lies only in the manner in which the secondary methylamine group is introduced into the structure of the drug.
The first way of synthesis is by the alkylation of 10,11-dihydro-5H-dibenz[b,f]azepine using 1-bromo-3-chloropropane in the presence of sodium amide into a chloro derivative (7.1.12) and the subsequent reaction of this with methylamine, giving desipramine (7.1.13) [18–20].

Finally, a second way of synthesis is from imipramine (7.1.1), which undergoes demethylation by successive reaction with ethyl chloroformate, giving 5-[3-(N-carbethoxy-N-methyl)aminopropyl]-10,11-dihydro-5H-dibenz[b,f]azepine (7.1.15), the alkaline hydrolysis of which leads to desipramine (7.1.13) [23,24].

Metabolism

Desipramine is extensively metabolized in the liver by CYP2D6 (major) and CYP1A2 (minor) to 2-hydroxydesipramine, an active metabolite. 2-hydroxydesipramine is thought to retain some amine reuptake inhibition and may possess cardiac depressant activity. The 2-hydroxylation metabolic pathway of desipramine is under genetic control.

Metabolism

Desipramine is a dihydrodibenzazepine secondary amine TCA that also is the active metabolite of imipramine. Desipramine appears to have a bioavailability comparable to the other secondary TCAs. Desipramine is distributed into milk in concentrations similar to those present at steady state in maternal plasma. This drug is metabolized primarily by CYP2D6 to its 2-hydroxy metabolite and by CYP1A2 and CYP2C19 to its N-demethylated (primary amine) metabolite . Desipramine exhibits a greater potency and selectivity for the NET than the other secondary TCAs do.