Clinical Overview
Imipramine pamoate is the long-acting formulation of imipramine, a tricyclic antidepressant indicated for depression. The pamoate salt allows for once-daily dosing, which may improve adherence compared to the immediate-release hydrochloride formulation that requires multiple daily doses.
Primary Clinical Applications
Imipramine pamoate is indicated for the relief of symptoms of depression, with endogenous depression being more likely to respond than other depressive states. It may be particularly useful for patients who have difficulty with medication adherence due to its once-daily dosing regimen.
Mechanism and Pharmacological Profile
Like other tricyclic antidepressants, imipramine pamoate inhibits the reuptake of norepinephrine and serotonin, with additional anticholinergic, antihistaminergic, and alpha-adrenergic blocking properties. The pamoate formulation provides sustained release, maintaining therapeutic levels throughout the day.
Clinical Considerations
The once-daily dosing of imipramine pamoate is typically given at bedtime to take advantage of its sedating properties and minimize daytime side effects. Patients should be established on the immediate-release formulation before switching to the pamoate form to ensure tolerability.
Prescribing Information
Dosing & Administration
Depression – Adults (Outpatients):
- Initial: 75 mg once daily at bedtime
- Titration: May increase gradually to 150 mg daily
- Maximum: 200 mg daily
Depression – Adults (Hospitalized):
- Initial: 100-150 mg once daily
- Maximum: 300 mg daily for severely ill patients
Elderly:
- Initial: 25-50 mg once daily at bedtime
- Titrate slowly based on response and tolerance
Administration:
- Give once daily, preferably at bedtime
- Swallow capsules whole, do not crush or chew
- Establish tolerance with immediate-release form first
Indications
- Relief of symptoms of depression
- Endogenous depression most likely to respond
Contraindications
- Hypersensitivity to tricyclic antidepressants
- Use within 14 days of MAOI therapy
- Acute recovery period following myocardial infarction
- Concurrent use with linezolid or IV methylene blue
Warnings & Precautions
- Boxed Warning: Increased risk of suicidal thoughts and behavior in patients under 25 years
- Cardiovascular effects: Monitor ECG in patients with cardiac disease
- Anticholinergic effects: Particularly problematic in elderly patients
- Seizure risk: Lower seizure threshold
- Angle-closure glaucoma: May precipitate acute attack
- Urinary retention: Risk in patients with prostatic hypertrophy
Drug Interactions
- MAOIs: Contraindicated – risk of serotonin syndrome
- CNS depressants: Enhanced sedation
- Anticholinergic drugs: Additive anticholinergic effects
- Type 1C antiarrhythmics: Additive cardiac effects
- CYP2D6 inhibitors: Increased imipramine levels
Adverse Reactions
Common (>10%):
- Drowsiness, dry mouth, constipation, blurred vision
- Dizziness, orthostatic hypotension, urinary retention
Cardiovascular:
- Tachycardia, palpitations, ECG changes
Serious:
- Cardiac arrhythmias, seizures, severe anticholinergic toxicity
Special Populations
- Elderly: Increased sensitivity to anticholinergic and cardiovascular effects
- Cardiac Disease: Requires careful monitoring and ECG surveillance
- Pregnancy: Category D – avoid in pregnancy
- Pediatric: Not recommended for children due to increased suicide risk
Medical Disclaimer: This information is for educational purposes only and is not intended as medical advice. Always consult with qualified healthcare professionals before making any treatment decisions. Individual patient circumstances may vary significantly.
