Generic Name: Imipramine Hydrochloride
Therapeutic Class: Tricyclic Antidepressant (TCA)
Indications
Imipramine Hydrochloride is a dibenzazepine derivative used for various psychological and physiological conditions:
- Depression: Treatment of various forms of depression, including endogenous depression, reactive depression, and depression associated with organic diseases.
- Nocturnal Enuresis: Treatment of bed-wetting in children (aged 6 years and above) after organic causes have been excluded.
- Panic Disorder: Effective in reducing the frequency of panic attacks, with or without agoraphobia.
- Chronic Pain: Occasionally used as adjuvant therapy for neuropathic pain and chronic tension-type headaches.
Dosage & Administration
Dosage must be individualized and increased cautiously under medical supervision.
- Depression (Adults): Initially 25 mg three times daily, gradually increased to 150–200 mg daily. Hospitalized patients may require up to 300 mg daily.
- Elderly: Start with 10 mg daily, increasing to 30–50 mg daily in divided doses.
- Childhood Enuresis:
- 6–7 years (20–25 kg): 25 mg daily.
- 8–11 years (25–35 kg): 25–50 mg daily.
- Over 11 years (35–54 kg): 50–75 mg daily.
Description & Pharmacokinetics
Imipramine is the prototype of the tricyclic antidepressant (TCA) group, acting as a potent neurotransmitter modulator.
Mechanism of Action: It primarily inhibits the neuronal reuptake of **Norepinephrine** and **Serotonin** (5-HT) from the synaptic cleft into the presynaptic terminals. This increases the concentration of these neurotransmitters at the postsynaptic receptors. It also possesses anticholinergic, antihistaminic, and alpha-1 adrenergic blocking activities.
Pharmacokinetics:
Mechanism of Action: It primarily inhibits the neuronal reuptake of **Norepinephrine** and **Serotonin** (5-HT) from the synaptic cleft into the presynaptic terminals. This increases the concentration of these neurotransmitters at the postsynaptic receptors. It also possesses anticholinergic, antihistaminic, and alpha-1 adrenergic blocking activities.
Pharmacokinetics:
- Absorption: Rapidly and well absorbed from the GI tract. Bioavailability is 22–77% due to significant first-pass metabolism.
- Metabolism: Extensively metabolized in the liver to its active metabolite, **Desipramine**.
- Distribution: Highly lipophilic and widely distributed throughout the body; 60–96% is bound to plasma proteins.
- Excretion: Approximately 80% is excreted in the urine and 20% in the feces, mainly as metabolites. The half-life ranges from 9 to 24 hours.
Side Effects
- Anticholinergic: Dry mouth, blurred vision, constipation, urinary retention, and increased intraocular pressure.
- Cardiovascular: Orthostatic hypotension (dizziness upon standing), tachycardia, and ECG changes (QT prolongation).
- CNS: Drowsiness, tremors, confusion (especially in elderly), and lowered seizure threshold.
- Metabolic: Weight gain and changes in blood sugar levels.
- Serious: Rare instances of bone marrow depression (agranulocytosis) and hepatic toxicity.
Extra Important Information: Usage Insights
- Suicidality: TCAs may increase the risk of suicidal thinking and behavior in children, adolescents, and young adults during early treatment.
- Tapering: Do not stop treatment abruptly; gradual reduction is required to avoid withdrawal symptoms like nausea and irritability.
- Therapeutic Lag: Antidepressant effects may take 2 to 4 weeks to become fully apparent.
Pregnancy & Lactation
- Pregnancy: Category D. There is evidence of potential fetal risk. Use only if life-saving and no safer alternatives exist.
- Lactation: Imipramine and its metabolite are excreted in breast milk. Breastfeeding is generally not recommended during therapy.
Precautions & Interactions
- MAOIs: Severe, even fatal, reactions can occur if taken with or within 14 days of Monoamine Oxidase Inhibitors.
- Alcohol: Potentiates the sedative and CNS depressant effects.
- Cardiac Disease: Use with extreme caution in patients with a history of myocardial infarction or arrhythmias.
Storage
Store at room temperature (20°C to 25°C). Keep in a dry place, protected from light. Ensure the container is child-resistant.
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