The prototypical tricyclic antidepressant. It has been used in major depression, dysthymia, bipolar depression, attention-deficit disorders, agoraphobia, and panic disorders. It has less sedative effect than some other members of this therapeutic group. .

Imipramina - Pharmacology:

Imipramina works by inhibiting the re-uptake of the neurotransmitters norepinephrine and serotonin by nerve cells. It binds the Sodium-dependent serotonin transporter and Sodium-dependent noradrenaline transporter, preventing or reducing the reuptake of norepinephrine and serotonin by nerve cells. As norepinephrine and serotonin are used to stimulate the synapse, and depression has been linked to a lack of stimulation of the recipient neuron at a synapse, slowing the reuptake of these neurotransmitters allows them to remain in the synaptic gap longer than it normal, increasing the stimulation of the recipient neuron and relieving the symptoms of depression. However, it does not act primarily by stimulation of the central nervous system. The clinical effect is also hypothesized as being due to potentiation of adrenergic synapses by blocking uptake of norepinephrine at nerve endings.

Imipramina for patients

Patients should be warned that imipramine hydrochloride may enhance the CNS depressant effects of alcohol

Patients taking imipramine hydrochloride should avoid excessive exposure to sunlight, since there have been reports of photosensitization.

Imipramina Interactions

In occasional susceptible patients or in those receiving anticholinergic drugs (including antiparkinsonism agents) in addition, the atropine-like effects may become more pronounced (e.g., paralytic ileus).

Close supervision and careful adjustment of dosage is required when this drug is administered concomitantly with anticholinergic drugs.

Avoid the use of preparations such as decongestants and local anesthetics which contain any sympathomimetic amine (e.g., epinephrine, norepinephrine), since it has been reported that tricyclic antidepressants can potentiate the effects of catecholamines.

Caution should be exercised when imipramine hydrochloride is used with agents that lower blood pressure. Imipramina hydrochloride may potentiate the effects of CNS depressant drugs.

The plasma concentration of imipramine may increase when the drug is given concomitantly with hepatic enzyme inhibitors (e.g., cimetidine, fluoxetine) and decrease by concomitant administration of hepatic enzyme inducers (e.g., barbiturates, phenytoin), and adjustment of the dosage of imipramine may therefore be necessary.

Drugs Metabolized by P450 2D6

The biochemical activity of the drug metabolizing isozyme cytochrome P450 2D6 (debrisoquin hydroxylase) is reduced in a subset of the caucasian population (about 7 to 10% of caucasians are so called "poor metabolizers"); reliable estimates of the prevalence of reduced P450 2D6 isozyme activity among Asian, African and other populations are not yet available. Poor metabolizers have higher than expected plasma concentrations of tricyclic antidepressants (TCAs) when given usual doses. Depending on the fraction of drug metabolized by P450 2D6, the increase in plasma concentration may be small, or quite large (8-fold increase in plasma AUC of the TCA).

In addition, certain drugs inhibit the activity of this isozyme and make normal metabolizers resemble p.o. metabolizers. An individual who is stable on a given dose of TCA may become abruptly toxic when given one of these inhibiting drugs as concomitant therapy. The drugs that inhibit cytochrome P450 2D6 include some that are not metabolized by the enzyme (quinidine; cimetidine) and many that are substrates for P450 2D6 (many other antidepressants, phenothiazines, and the Type 1C antiarrhythmics propafenone and flecainide). While all the selective serotonin reuptake inhibitors (SSRIs), e. g., fluoxetine, sertraline, and paroxetine, inhibit P450 2D6, they may vary in the extent of inhibition. The extent to which SSRI-TCA interactions may pose clinical problems will depend on the degree of inhibition, and the pharmacokinetics of the SSRI involved. Nevertheless, caution is indicated in the co-administration of TCA5 with any of the SSRIs and also in switching from one class to the other. Of particular importance, sufficient time must elapse before initiating TCA treatment in a patient being withdrawn from fluoxetine, given the long half-life of the parent and active metabolite (at least 5 weeks may be necessary).

Concomitant use of tricyclic antidepressants with drugs that can inhibit cytochrome P450 2D6 may require lower doses than usually prescribed for either the tricyclic antidepressant or the other drug. Furthermore, whenever one of these other drugs is withdrawn from cotherapy, an increased dose of tricyclic antidepressant may be required. It is desirable to monitor TCA plasma levels whenever a TCA is going to be co-administered with another drug known to be an inhibitor of P450 2D6.

Imipramina Contraindications

The concomitant use of monoamine oxidase inhibiting compounds is contraindicated. Hyperpyretic crises or severe convulsive seizures may occur in patients receiving such combinations. The potentiation of adverse effects can be serious or even fatal. When it is desired to substitute imipramine hydrochloride in patients receiving a monoamine oxidase inhibitor, as long an interval should elapse as the clinical situation will allow, with a minimum of 14 days. Initial dosage should be low and increases should be gradual and cautiously prescribed.

The drug is contraindicated during the acute recovery period after a myocardial infarction. Patients with a known hypersensitivity to this compound should not be given the drug. The possibility of cross-sensitivity to other dibenzazepine compounds should be kept in mind.

Generic name, Overdose, Half Life Imipramina, Food Interactions, Chemical, etc..

Imipramina see also Hibiscus flowers