mirtazapine

mirtazapine

(mer tah' zah peen)

Remeron, Remeron SolTab

Pregnancy Category C

Drug class

Antidepressant (tetracyclic)

Therapeutic actions

Mechanism of action unknown; appears to act similarly to TCAs, which inhibit the presynaptic reuptake of the neurotransmitters norepinephrine and serotonin;anticholinergic at CNS and peripheral receptors; sedating; relation of these effects to clinical efficacy is unknown.

Indication

·        Relief of symptoms of depression (endogenous depression most responsive)

Contraindications and cautions

·        Contraindicated with hypersensitivity to any tricyclic or tetracyclic drug; concomitant therapy with an MAOI; recent MI; myelography within previous 24 hr or scheduled within 48 hr; pregnancy (limb reduction abnormalities reported); lactation

·        Use cautiously with ECT; preexisting CV disorders (eg, severe coronary heart disease, progressive heart failure, angina pectoris, paroxysmal tachycardia [possible increased risk of serious CVS toxicity with TCAs]); angle-closure glaucoma, increased IOP, urinary retention, ureteral or urethral spasm; seizure disorders (TCAs lower the seizure threshold); hyperthyroidism (predisposes to CVS toxicity, including cardiac arrhythmias); impaired hepatic, renal function; psychiatric patients (schizophrenic or paranoid patients may exhibit a worsening of psychosis with TCAs); manic-depressive disorder (may shift to hypomanicor manic phase); elective surgery (TCAs should be discontinued as long as possible before surgery)

Available forms

Tablets—15, 30, 45 mg; orally disintegrating tablet—15, 30, 45 mg

Dosages

ADULTS

Initial dose, 15 mg PO daily, as a single dose in evening. May be increased up to 45 mg/day as needed. Change dose only at intervals greater than 1–2 wk. Continue treatment for up to 6 mo for acute episodes.

·        Switching from MAOI: Allow at least 14 days between discontinuation of MAOI and beginning of mirtazapine therapy. Allow 14 days after stoppingmirtazapine before starting MAOI.

PEDIATRIC PATIENTS

Not recommended in patients < 18 yr.

GERIATRIC PATIENTS AND PATIENTS WITH RENAL OR HEPATIC DYSFUNCTION

Give lower doses to patients > 60 yr.

Pharmacokinetics

Route	Onset	Peak	Duration
Oral	Slow	2–4 hr	2–4 wk

Metabolism: Hepatic; T_1/2: 20–40 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Feces, urine

Adverse effects

·        CNS: Sedation and anticholinergic (atropine-like) effects; confusion (especially in elderly), disturbed concentration, hallucinations, disorientation, decreased memory, feelings of unreality, delusions, anxiety, nervousness, restlessness, agitation, panic, insomnia, nightmares, hypomania, mania, exacerbation of psychosis, drowsiness, weakness, fatigue, headache, numbness, agitation (less likely with this drug than with other antidepressants)

·        CV: Orthostatic hypotension, hypertension, syncope, tachycardia, palpitations, MI, arrhythmias, heart block, precipitation of CHF, stroke

·        Endocrine: Elevated or depressed blood sugar; elevated prolactin levels; inappropriate ADH secretion

·        GI: Dry mouth, constipation, paralytic ileus, nausea (less likely with this drug than with other antidepressants), increased appetite, weight gain, vomiting, anorexia, epigastric distress, diarrhea, flatulence, dysphagia, peculiar taste, increased salivation, stomatitis, glossitis, parotid swelling, abdominal cramps, black tongue, liver enzyme elevations

·        GU: Urinary retention, delayed micturition, dilation of urinary tract, gynecomastia, testicular swelling in men; breast enlargement, menstrual irregularity,galactorrhea in women; increased or decreased libido; impotence

·        Hematologic: Agranulocytosis, neutropenia

·        Hypersensitivity: Rash, pruritus, vasculitis, petechiae, photosensitization, edema

Interactions

Drug-drug

·        WARNING: Risk of serious, sometimes fatal reactions if combined with MAOIs; do not use this combination or within 14 days of MAOI therapy

Nursing considerations

Assessment

·        History: Hypersensitivity to any antidepresssant; concomitant therapy with MAOI; recent MI; myelography within previous 24 hr or scheduled within 48 hr; lactation; ECT; preexisting CV disorders; angle-closure glaucoma; increased IOP, urinary retention, ureteral or urethral spasm; seizure disorders; hyperthyroidism; impaired hepatic, renal function; psychiatric problems; manic-depressive patients; elective surgery; pregnancy, lactation

·        Physical: Body weight; T; skin color, lesions; orientation, affect, reflexes, vision and hearing; P, BP, orthostatic BP, perfusion; bowel sounds, normal output, liver evaluation; urine flow, normal output; usual sexual function, frequency of menses, breast and scrotal examination; LFTs, urinalysis, CBC, ECG

Interventions

·        WARNING: Ensure that depressed and potentially suicidal patients have access only to limited quantities of the drug.

·        Administer orally disintegrating tablets to patients who have difficulty swallowing: Open blister pack and have patient place tablet on tongue. Do not split tablet.

·        Expect clinical response in 3–7 days up to 2–3 wk (latter is more usual).

·        Arrange for CBC if patient develops fever, sore throat, or other sign of infection during therapy.

·        Establish safety precautions if CNS changes occur (use side rails, accompany patient when ambulating).

Teaching points

·        Take this drug exactly as prescribed; do not stop taking the drug abruptly or without consulting your health care provider.

·        Place orally disintegrating tablet on tongue; it can be swallowed without water. Open blister pack with dry hands and use tablet immediately; do not cut or break tablet.

·        Avoid using alcohol, other sleep-inducing drugs, or over-the-counter drugs while using this drug.

·        Avoid prolonged exposure to sunlight or sunlamps; use a sunscreen or protective garments if long exposure to sunlight is unavoidable.

·        You may experience these side effects: Headache, dizziness, drowsiness, weakness, blurred vision (reversible; avoid driving or performing tasks that require alertness); nausea, vomiting, loss of appetite, dry mouth (eat frequent small meals; use frequent mouth care, suck on sugarless candies); nightmares, inability to concentrate, confusion; changes in sexual function.

·        Report fever, flulike illness, any infection, dry mouth, difficulty urinating, excessive sedation, suicidal thoughts.

Adverse effects in Italic are most common; those in Bold are life-threatening.