TRIMIPRAMINE 10 mg BLISS

Indications

• Depressive illness
• Neuropathic pain (off-label use)
• Migraine prophylaxis (off-label use)

Dosage

Adults: Initially, 10 mg once daily, usually taken at night. The dose may be increased if necessary to 75

Mechanism of action

Trimipramine acts by decreasing the reuptake of norepinephrine and serotonin (5-HT), which are neurotransmitters involved in mood regulation. This mechanism is distinct from other tricyclic antidepressants, leading to potential variations in therapeutic effects and side effects.

Pharmacodynamics

As a tricyclic antidepressant, trimipramine affects the neurotransmitter systems in the brain. Although the reuptake inhibition occurs rapidly, the antidepressant effect typically manifests after a delay of about two weeks. This delay is thought to result from changes in receptor sensitivity within the cerebral cortex and hippocampus. The medication sensitizes presynaptic a1 and b1 receptors while desensitizing a2 receptors, which may lead to increased production of noradrenaline. Additionally, trimipramine exhibits analgesic properties by modulating central nervous system pathways involved in pain regulation, though the exact mechanism remains unclear.

Pharmacokinetics

Trimipramine is well-absorbed following oral administration, with peak plasma concentrations typically reached within 2 to 6 hours. It demonstrates a large volume of distribution and is extensively metabolized in the liver, primarily through cytochrome P450 enzymes. The drug has a long half-life, allowing for once-daily dosing in many cases. Trimipramine is primarily excreted in urine, with a small proportion eliminated unchanged. Considerations for dosage adjustment may be necessary in patients with hepatic impairment or the elderly due to altered pharmacokinetics.

Contra-indications

• Arrhythmias
• During the manic phase of bipolar disorder
• Heart block
• Immediate recovery period after myocardial infarction
• Severe hepatic impairment
• History of alcohol abuse
• Prostatic hypertrophy
• Susceptibility to angle-closure glaucoma

Adverse effects

• Drowsiness
• Dry mouth
• Constipation
• Urinary retention
• Dilated pupils
• Convulsions
• Respiratory failure
• Cardiac conduction defects
• Arrhythmias
• Increased risk of suicide

Interactions

• Enhanced effects when combined with alcohol
• Increased risk of side effects with other CNS depressants
• Potentially hazardous interactions with monoamine oxidase inhibitors (MAOIs)

Precautions

• Use with caution in patients with cardiovascular disease
• Patients with diabetes should be monitored closely
• Elderly patients may be more susceptible to side effects
• Treatment should be stopped if the patient enters a manic phase

Pregnancy

Use only if potential benefit outweighs risk.

Breast-feeding

The amount secreted into breast milk is too small to be harmful.

Storage

Store in a cool, dry place away from light.

Formulations

• Oral suspension
• Oral solution
• Tablets

Mechanism of action

Trimipramine's mechanism of action differs from other tricyclic antidepressants. Trimipramine acts by decreasing the reuptake of norepinephrine and serotonin (5-HT).

Pharmacodynamics

Trimipramine is a tricyclic antidepressant. It was thought that tricyclic antidepressants work by inhibiting the re-uptake of the neurotransmitters norepinephrine and serotonin by nerve cells. However, this response occurs immediately, yet mood does not lift for around two weeks. It is now thought that changes occur in receptor sensitivity in the cerebral cortex and hippocampus. The hippocampus is part of the limbic system, a part of the brain involved in emotions. Presynaptic receptors are affected: a1 and b1 receptors are sensitized, a2 receptors are desensitised (leading to increased noradrenaline production). Tricyclics are also known as effective analgesics for different types of pain, especially neuropathic or neuralgic pain. A precise mechanism for their analgesic action is unknown, but it is thought that they modulate anti-pain opioid systems in the CNS via an indirect serotonergic route. They are also effective in migraine prophylaxis, but not in abortion of acute migraine attack. The mechanism of their anti-migraine action is also thought to be serotonergic.