PROTRIPTYLINE

Toxicity

Side effects include anxiety, blood disorders, confusion, decreased libido, dizziness, flushing, headache, impotence, insomnia, low blood pressure, nightmares, rapid or irregular heartbeat, rash, seizures, sensitivity to sunlight, stomach and intestinal discomfort, sedation, hypotension, blurred vision, dry mouth, constipation, urinary retention, postural hypotension, tachycardia, hypertension, ECG changes, heart failure, impaired memory and delirium, and precipitation of hypomanic or manic episodes in bipolar depression. Withdrawal symptoms include gastrointestinal disturbances, anxiety, and insomnia.

The Uses of PROTRIPTYLINE

Protriptyline is a powerful antidepressant, the mechanism of action of which is not known. It is not a MAO inhibitor and does not stimulate the CNS. It begins to act much faster and acts much longer than imipramine or amitriptyline. Protriptyline does not possess sedative tranquilizing properties. It is used in clinical conditions for treating severe depression.

The Uses of PROTRIPTYLINE

Antidepressant.

Background

Protriptyline hydrochloride is a dibenzocycloheptene-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, protriptyline does not affect mood or arousal, but may cause sedation. In depressed individuals, protriptyline exerts a positive effect on mood. TCAs are potent inhibitors of serotonin and norepinephrine reuptake. In addition, TCAs 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, alpha1-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. Protriptyline may be used for the treatment of depression.

Indications

For the treatment of depression.

Definition

ChEBI: Protriptyline is a carbotricyclic compound. It has a role as an antidepressant. It derives from a hydride of a dibenzo[a,d][7]annulene.

brand name

Vivactil (Odyssey).

Mechanism of action

Protriptyline exhibits high selectivity for the NE transporter, but with less potency than desipramine. Its mechanism of action is similar to that of desipramine. Minimal effect on 5-HT reuptake has been observed.

Pharmacokinetics

Protriptyline is a tricyclic antidepressant. It was thought that tricyclic antidepressants work by inhibiting the reuptake of the neurotransmitters norepinephrine and serotonin by nerve cells. The effectiveness of antidepressants appear after approximately two weeks following recommended adminsitration schedule. Gradual changes are thought to occur in the cerebral cortex and hippocampus, involved in emotion regulation as part of the limbic system, as receptor sensitivity is enhanced. While α1 and β1 receptors are sensitized, α2 receptors are desensitized (leading to increased noradrenaline production). Tricyclics are also reported to alter the perceptions of pain, including neuropathic or neuralgic pain, so they may exhibit analgesic properties. The mechanism of action behind this analgesic property is not fully understood; however, it is thought to involve modulation of endogenous opioid systems in the CNS via an indirect serotonergic route. Tricyclic antidepressants are also effective in relieving migraine prophylaxis, but not in abortion of acute migraine attack, potentially via their serotonergic effects.

Synthesis

Protriptyline, N-methyl-5-H-dibenzo[a,d]cyclohepten-5-propylamine (7.1.22), differs from all of the drugs described above in that there is present a double bond at the C10¨CC11 position of the central 7-membered ring of the tricyclic part of the molecule. At the same time, a free electron pair on C5 belonging to either a nitrogen atom or an exocyclic double bond are excluded, which undoubtedly changes both the architecture of the whole molecule as well as, the collocation of pharmacophore groups.
Protriptyline is synthesized by alkylation of 5-H-dibenzo[a,d]cycloheptene with 3-(Nphormyl-N-methylamino)propylchloride (7.1.20), which is synthesized from compound (7.1.19). The resulting intermediate product (7.1.21) undergoes alkaline hydrolysis, which leads to the formation of protriptyline (7.1.21) [33¨C38].

Metabolism

Not Available

Metabolism

Protriptyline is a dibenzocycloheptriene TCA that differs from the other tricyclics by having an unsaturated ethylene bridge joining the two aromatic rings and a secondary aminopropyl side chain. Protriptyline is completely absorbed from the GI tract and slowly eliminated. Metabolism data are limited for protriptyline, but it is most likely to be metabolized via the same pathways as the other TCAs are. Very little drug is excreted in the feces via the bile.