Imipramine

Imipramine, sold under the is a tricyclic antidepressant (TCA) which is used mainly in the treatment of depression.

Brand name Tofranil among others,

Also effective in treating anxiety and panic disorder.

The drug is also used to treat bedwetting.

An oral agent, but a long-acting form for injection into muscle is also available.

Pregnancy category US: N (Not classified yet).

Bioavailability 94–96%.

Protein binding 86%.

Hepatic metabolism, CYP1A2, CYP2C19, CYP2D6 enzymes

Metabolite-Desipramine

Elimination half-life20 hours

Excretion-renal (80%), fecal (20%)

Common side effects include: dry mouth, drowsiness, dizziness, low blood pressure, rapid heart rate, urinary retention, and electrocardiogram changes.

Overdose can result in death.

It work by increasing levels of serotonin and norepinephrine and by blocking certain serotonin, adrenergic, histamine, and cholinergic receptors.

It was the first TCA to be marketed.

Its use in recent decades has declined due to the introduction of the selective serotonin reuptake inhibitors (SSRIs), which have fewer side effects and are safer in overdose.

It is used in the treatment of depression and certain anxiety disorders.

Also used to treat nocturnal enuresis because of its ability to shorten the time of delta wave stage sleep, where wetting occurs.

Blood levels between 150-250 ng/mL of imipramine generally correspond to antidepressant efficacy.

It is available in the form of oral tablets and as a formulation for depot intramuscular injection.

Adding it alcohol consumption causes excessive drowsiness.

It may be unsafe during pregnancy.

Side effects:
Central nervous system: dizziness, drowsiness, confusion, seizures, headache, anxiety, tremors, stimulation, weakness, insomnia, nightmares, extrapyramidal symptoms in geriatric patients, increased psychiatric symptoms, paresthesia

Cardiovascular: orthostatic hypotension, ECG changes, tachycardia, hypertension, palpitations, dysrhythmias

Eyes, ears, nose and throat: blurred vision, tinnitus, mydriasis

Gastrointestinal: dry mouth, nausea, vomiting, paralytic ileus, increased appetite, cramps, epigastric distress, jaundice, hepatitis, stomatitis, constipation, taste change

Genitourinary: urinary retention

Hematological: agranulocytosis, thrombocytopenia, eosinophilia, leukopenia

Skin: rash, urticaria, diaphoresis, pruritus, photosensitivity

It affects numerous neurotransmitter systems involved in the etiology of depression, anxiety, attention-deficit hyperactivity disorder (ADHD), enuresis and numerous other mental and physical conditions.

Has a similar structure to some muscle relaxants, and has a significant analgesic effect.

The mechanisms of actions include:

Serotonin: very strong reuptake inhibition.

Norepinephrine: strong reuptake inhibition.

Dopamine: imipramine blocks D2 receptors.

It is an anticholinergic, specifically an antagonist of the muscarinic acetylcholine receptors.

In the elderly and in patients with psychosis it is used with caution, as the general brain activity enhancement in combination with the dementing effects of anticholinergics increases the potential to cause hallucinations, confusion and delirium in this population.

It antagonizes adrenergic receptors, thus sometimes causing orthostatic hypotension.

Imipramine is an antagonist of the histamine H1 receptors.

It is converted into desipramine as a metabolite.

It may cause a high rate of manic and hypomanic reactions in patients with pre-existing bipolar disorder, with one study showing that up to 25% of such patients maintained on Imipramine switched into mania or hypomania.

It is still prescribed as a second-line treatment for treating major depression.

It has limited use in the treatment of migraines, ADHD, and post-concussive syndrome, panic attacks, chronic pain, and Kleine-Levin syndrome.

In pediatric patients, it is used to treat nocturnal enuresis.

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