Mirtazapine is an atypical antidepressant which is used primarily in the treatment of depression. Less commonly it is used to treat anxiety disorders, insomnia, nausea and vomiting, and to produce weight gain.
Pharmacodynamics: The mechanism of action of Mirtazapine as with other drugs effective in the treatment of major depressive disorder is unknown. Evidence gathered in preclinical studies suggests that Mirtazapine enhances central noradrenergic and serotonergic activity. These studies have shown that Mirtazapine acts as an antagonist at central presynaptic α2-adrenergic inhibitory autoreceptors and heteroreceptors, an action that is postulated to result in an increase in central noradrenergic and serotonergic activity. Mirtazapine is a potent antagonist of 5- HT2 and 5-HT3 receptors. Mirtazapine has no significant affinity for the 5-HT1A and 5-HT1B receptors. Mirtazapine is a potent antagonist of histamine (H1) receptors, a property that may explain its prominent sedative effects. Mirtazapine is a moderate peripheral α1-adrenergic antagonist, a property that may explain the occasional orthostatic hypotension reported in association with its use. Mirtazapine is a moderate antagonist at muscarinic receptors, a property that may explain the relatively low incidence of anticholinergic side effects associated with its use.
Pharmacokinetics: After oral administration of Mirtazapine tablets, the active constituent mirtazapine is rapidly and well-absorbed, reaching peak plasma levels after about 2 hours. Binding of mirtazapine to plasma proteins is approximately 85%. The mean half-life of elimination is 20-40 hours; (26 hours in males, 37 hours in females). The half-life of elimination is sufficient to justify once-a-day dosing. Mirtazapine displays linear pharmacokinetics within the recommended dose range. Mirtazapine is extensively metabolized and eliminated via the urine and faeces four days. Major pathways of biotransformation are demethylation and oxidation followed by conjugation.
Major depression BY MOUTH Adult: Initially 15-30 mg daily for 2-4 weeks, dose to be taken at bedtime, then adjusted according to response to up to 45 mg once daily, alternatively up to 45 mg daily in 2 divided doses
Mirtazapine has clinically significant drug-drug interactions with Monoamine Oxidase Inhibitors (MAOI) & other serotonergic drugs such as tryptophan, triptans, linezolid, serotonin reuptake inhibitors, venlafaxine, lithium, tramadol, or St. John's wort. Mirtazapine may interrupt the metabolism or activity of Carbamazepine, Phenytoin or Cimetidine. Patient should avoid Alcohol & Diazepam while taking Mirtazapine.
Cardiac disorders . diabetes mellitus . elderly . history of bipolar depression . history of seizures . history of urinary retention . hypotension . psychoses (may aggravate psychotic symptoms) . susceptibility to angleclosure glaucoma
Common or very common Abnormal dreams . agitation (on withdrawal) . anxiety . anxiety (on withdrawal) . arthralgia . confusion . dizziness . dizziness (on withdrawal) . drowsiness . dry mouth . fatigue . headache (on withdrawal) . increased appetite . insomnia . myalgia . nausea (on withdrawal) . oedema . postural hypotension . tremor . vomiting (on withdrawal) . weight gain Uncommon Hallucinations . mania . movement disorders . syncope Rare Aggression . myoclonus . pancreatitis Frequency not known Angle-closure glaucoma . blood disorders . convulsions . dysarthria . hypersalivation . hyponatraemia . inappropriate secretion of antidiuretic hormone . sedation during initial treatment . Stevens- Johnson syndrome . suicidal behaviour . toxic epidermal necrolysis
PREGNANCY Use with caution?limited experience; monitor neonate for withdrawal effects. BREAST FEEDING Present in milk; use only if potential benefit outweighs risk.
Keep away from light and moisture. Store below 30º C. Keep all medicine out of the reach of children.
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