Mirtazapine

BRAND NAMES

Remeron: It contains the active ingredients of mirtazapine. It is available in the form of oral film-coated tablets used to treat depression.

Remeron Sol Tab: It contains the active ingredients of mirtazapine. It is available in the form of disintegrated tablets used to treat depression.

MECHANISM OF ACTION

Mirtazapine is a tetracyclic antidepressant medication. Mirtazapine inhibits central presynaptic alpha-2-adrenergic receptors, enhancing serotonin and norepinephrine release. Mirtazapine is also known as a noradrenergic and selective serotonergic antidepressant. Noradrenaline is known to activate the sympathetic nervous system, which explains why mirtazapine causes general increases in activity and metabolism. It is also an effective antagonist of H1 histamine receptors 5-HT2A, 5-HT2C, and 5-HT3 serotonin receptors.

PHARMACOKINETICS

ABSORPTION

Mirtazapine is readily absorbed, reaching maximal plasma concentration in 2 hours. Food has a minor influence on both the rate and extent of absorption, necessitating no mirtazapine dose change.

DISTRIBUTION

In a pharmacokinetics investigation, the volume of distribution following an oral steady-state dose was found to be 107±42L.

METABOLISM

Mirtazapine is extensively metabolized in the liver by demethylation, hydroxylation, conjugation, and the cytochrome P450 enzyme. One of its key metabolites is desmethyl mirtazapine.

EXCRETION

The average elimination half-life of mirtazapine ranges from 20 to 40 hours. Mirtazapine metabolites are mostly eliminated in urine (75%), with feces accounting for 15%.

PHARMACODYNAMICS

Mirtazapine is a conventional antidepressant that is primarily used to treat severe depressive disorders. Mirtazapine belongs to the class of antidepressants known as tetracyclics. Mirtazapine inhibits central presynaptic alpha-2-adrenergic receptors, enhancing serotonin and norepinephrine release.

DOSAGE AND ADMINISTRATION

Mirtazapine is available in two forms: tablets and disintegrating tablets for oral use. It is typically taken once per day at bedtime. It can be taken with or without meals. Mirtazapine tablets are available in strengths of 7.5 mg, 15 mg, 30 mg, and 45 mg.

They are disintegrating tablets in strengths of 15 mg, 30 mg, and 45 mg.

DRUG INTERACTIONS

Drug interaction of mirtazapine includes

• Anti-depressants: moclobemide, tranylcypromine, selegiline, duloxetine, sertraline and escitalopram
• Antibiotics: erythromycin and linezolid
• Anti-fungal: ketoconazole
• Anti-tuberculosis: rifampicin
• Anti-psychotics: olanzapine, aripiprazole, and quetiapine
• Anti-convulsant: carbamazepine, phenytoin, and pregabalin
• Pain relievers: tramadol, morphine, acetaminophen, and hydrocodone
• Anti-anxiety: alprazolam
• Anti-hypertensive: metoprolol.

CONTRAINDICATIONS

You shouldn't use mirtazapine if you have an allergy to any of its constituents. Mirtazapine should not be given to patients undergoing intravenous methylene blue or linezolid due to the increased risk of serotonin syndrome.

SIDE EFFECTS

Mirtazapine side effects may include

• Drowsiness
• Dizziness
• Anxiousness
• Confusion
• Increased weight and appetite
• Dry mouth
• Nausea
• Vomiting
• constipation

Some serious side effects may include

• flu-like symptoms—fever, chills, sore throat, mouth sores, or other signs of infection.
• Chest pain
• Fast heartbeat
• seizures

OVERDOSE

Common overdose symptoms include 

• drowsiness 
• mild tachycardia 
• hypertension 
• higher risk of CNS depression if more than 1000 mg are consumed

TOXICITY

Activated charcoal should be given during an overdose to absorb excess Mirtazapine. General supportive therapy should be used, including maintaining an adequate airway. Oxygen and ventilation therapy.