THIORIDAZINE HYDROCHLORIDE

THIORIDAZINE HYDROCHLORIDE
(thye-o-rid'a-zeen)
Novoridazine 
Classifications: psychotherapeutic; phenothiazine antipsychotic;
Therapeutic: antipsychotic

Prototype: Chlorpromazine
Pregnancy Category: C

Availability

10 mg, 15 mg, 25 mg, 50 mg, 100 mg, 150 mg, 200 mg tablets; 30 mg/mL, 100 mg/mL solution; 25 mg/5 mL suspension

Action

A phenothiazine that rarely produces extrapyramidal effects. Thioridazine blocks postsynaptic dopamine receptors in the mesolimbic system of the brain. The decrease in dopamine neurotransmission has been found to correlate to the antipsychotic effects.

Therapeutic Effect

Effective in reducing excitement, hypermotility, abnormal initiative, affective tension, and agitation by inhibiting psychomotor functions. Also effective as an antipsychotic agent, and for behavioral disorders in children.

Uses

Management of nonpsychotic behavioral disturbances of senility, manifestations of psychotic disorders, alcohol withdrawal; symptomatic treatment of organic brain disease. Short-term treatment of moderate to marked depression and for management of hyperkinetic behavior syndrome (attention deficit disorder).

Contraindications

Hypersensitivity to phenothiazines. Severe CNS depression; CV disease; family history of QT prolongation; suicidal ideation; children <2 y; pregnancy (category C), lactation.

Cautious Use

Premature ventricular contractions; previously diagnosed breast cancer; patients exposed to extremes in heat or to organophosphorus insecticides; history of suicidal ideation; Parkinson's disease; seizure disorders; closed-angle glaucoma; respiratory disorders.

Route & Dosage

Psychotic Disorders
Adult: PO 50–100 mg t.i.d., may increase up to 800 mg/d as needed or tolerated
Geriatric: PO 10 mg t.i.d., may increase up to 200 mg/d
Child (>2 y) : PO 0.5–3 mg/kg/d in divided doses; if hospitalized, may start at 25 mg t.i.d.

Moderate to Marked Depression
Adult: PO 25 mg t.i.d., may increase up to 200 mg/d in divided doses

Dementia Behavior
Geriatric: PO 10–25 mg 1–2 times/d, may increase q4–7d (max: 400 mg/d in divided doses)

Administration

Oral
  • Give with fluid of patient's choice; tablet may be crushed.
  • Schedule phenothiazine at least 1 h before or 1 h after an antacid or antidiarrheal medication.
  • Dilute liquid concentrate just prior to administration with ? glass of fruit juice, milk, water, carbonated beverage, or soup.
  • Add increases in dose to the first dose of the day to prevent sleep disturbance.
  • Store at 15°–30° C (59°–86° F) in tightly covered, light-resistant containers unless otherwise indicated.

Adverse Effects (≥1%)

CNS: Sedation, dizziness, drowsiness, lethargy, extrapyramidal syndrome, nocturnal confusion, hyperactivity. Special Senses: Nasal congestion, blurred vision, pigmentary retinopathy. GI: Xerostomia, constipation, paralytic ileus. Urogenital: Amenorrhea, breast engorgement, gynecomastia, galactorrhea, urinary retention. CV: Ventricular dysrhythmias, hypotension, prolonged QTc interval.

Interactions

Drug: Alcohol, anxiolytics, sedative-hypnotics, other cns depressants add to CNS depression; additive adverse effects with other phenothiazines; amiodarone, amoxapine, arsenic trioxide, bepridil, clarithromycin, daunorubicin, diltiazem, disopyramide, dofetilide, dolasetron, doxorubicin, encainide, erythromycin, flecainide, fluoxetine, fluvoxamine gatifloxacin, grepafloxacin, haloperidol, ibutilide, indapamide, local anesthetics, maprotiline, moxifloxacin, octreotide, paroxetine, pentamidine, pimozide, procainamide, probucol, quinidine, risperidone, sotalol, sertraline, sparfloxacin, terodiline, tocainide, tricyclic antidepressants, venlafaxine, verapamil, ziprasidone can prolong QTc interval resulting in arrhythmias. Herbal: Kava may increase risk and severity of dystonic reactions.

Pharmacokinetics

Absorption: Well absorbed from GI tract. Onset: Days to weeks. Distribution: Crosses placenta; distributed into breast milk. Metabolism: In liver. Elimination: In urine. Half-Life: 26–36 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor for changes in behavior that may indicate increased possibility of suicidality.
  • Orthostatic hypotension may occur in early therapy. Female patients appear to be more susceptible than males.
  • Be aware that patients may be unable to adjust to extremes of temperature because drug effects heat regulatory center in the hypothalamus. Patient may complain of being cold even at average room temperature; older adults are particularly susceptible.
  • Monitor I&O ratio and bowel elimination pattern. Check for abdominal distention and pain. Encourage adequate fluid intake as prophylaxis for constipation and xerostomia. The depressed patient may not seek help for either symptom or for urinary retention.
  • Lab tests: Obtain periodic CBC and liver function tests during therapy.
  • Supervise patient closely during early course of therapy. Suicide is an inherent risk with any depressed patient and may remain a problem until there is significant clinical improvement.

Patient & Family Education

  • Exercise care not to spill drug on skin because of danger of contact dermatitis. Wash skin well in soap and water if liquid drug is spilled.
  • Take drug as prescribed and do not alter dosing regimen or stop medication without consulting physician.
  • Avoid alcohol during phenothiazine therapy. Concomitant use enhances CNS depression effects.
  • Be aware that marked drowsiness generally subsides with continued therapy or reduction in dosage.
  • Do not drive or engage in potentially hazardous activities until response to drug is known.
  • Make position changes slowly, particularly from lying down to upright posture; dangle legs a few minutes before standing.
  • Vasodilation produced by hot showers or baths or by long exposure to environmental heat may accentuate hypotensive effect.
  • Do not apply heating pad or hot water bottles to the body for external heat. Because of depressed conditioned avoidance behaviors, a severe burn may result.
  • Report the onset of any change in visual acuity, brownish coloring of vision, or impairment of night vision to physician. Symptoms suggest pigmentary retinopathy (observed primarily in patients receiving extremely high doses). An ophthalmic consultation may be indicated.
  • Note: Thioridazine may color urine pink-red to reddish brown.
  • Do not use any OTC drugs unless approved by the physician.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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