Mesoridazine: side effects How Drug Causes Side Effects

• By blocking dopamine 2 receptors in the striatum, it can cause motor side effects

• By blocking dopamine 2 receptors in the pituitary, it can cause elevations in prolactin

• By blocking dopamine 2 receptors excessively in the mesocortical and mesolimbic dopamine pathways, especially at high doses, it can cause worsening of negative and cognitive symptoms (neuroleptic-induced deficit syndrome)

• Anticholinergic actions may cause sedation, blurred vision, constipation, dry mouth

• Antihistaminic actions may cause sedation, weight gain

• By blocking alpha 1 adrenergic receptors, it can cause dizziness, sedation, and hypotension

• Mechanism of weight gain and any possible increased incidence of diabetes or dyslipidemia with conventional antipsychotics is unknown

✽ Mechanism of potentially dangerous QTc prolongation may be related to actions at ion channels

Notable Side Effects

✽ Neuroleptic-induced deficit syndrome

✽ Akathisia

✽ Priapism

✽ Extrapyramidal symptoms, parkinsonism, tardive dyskinesia

✽ Galactorrhea, amenorrhea

✽ Pigmentary retinopathy at high doses

• Dizziness, sedation

• Dry mouth, constipation, blurred vision

• Decreased sweating

• Sexual dysfunction

• Hypotension

• Weight gain

Life-Threatening or Dangerous Side Effects

• Rare neuroleptic malignant syndrome

• Rare jaundice, agranulocytosis

• Rare seizures

✽ Dose-dependent QTc prolongation

• Ventricular arrhythmias and sudden death

• Increased risk of death and cerebrovascular events in elderly patients with dementia-related psychosis

Weight Gain

• Occurs in significant minority

Sedation

• Many experience and/or can be significant in amount

• Sedation is usually transient

What to Do About Side Effects

• Wait

• Wait

• Wait

• For motor symptoms, add an anticholinergic agent

• Reduce the dose

• For sedation, give at night

• Switch to an atypical antipsychotic

• Weight loss, exercise programs, and medical management for high BMIs, diabetes, dyslipidemia

Best Augmenting Agents for Side Effects

• Augmentation of mesoridazine has not been systematically studied and can be dangerous

MESORIDAZINE: DOSING AND USE

Usual Dosage Range

• Oral: 100–400 mg/day

• Injection: 25–200 mg/day

Dosage Forms

• Tablet 10 mg, 25 mg, 50 mg, 100 mg

• Ampul 25 mg/mL, 1 mL

• Concentrate 25 mg/mL

How to Dose

• Oral: initial 50 mg 3 times a day; increase dose cautiously as needed

• Injection: initial 25 mg; repeat after 30–60 minutes if needed

• Take liquid formulation in water, orange juice, or grapefruit juice

Dosing Tips

✽ The effects of mesoridazine on the QTc interval are dose-dependent, so start low and go slow while carefully monitoring QTc interval

• Treatment should be suspended if absolute neutrophil count falls below 1,000/mm³

Overdose

• Deaths have occurred; sedation, confusion, agitation, respiratory depression, cardiac disturbances, coma

Long-Term Use

• Some side effects may be irreversible (e.g., tardive dyskinesia)

Habit Forming

• No

How to Stop

• Slow down-titration of oral formulation (over 6–8 weeks), especially when simultaneously beginning a new antipsychotic while switching (i.e., cross-titration)

• Rapid oral discontinuation may lead to rebound psychosis and worsening of symptoms

• If antiparkinson agents are being used, they should be continued for a few weeks after mesoridazine is discontinued

Pharmacokinetics

• Half-life approximately 2–9 hours

Drug Interactions

• May decrease the effects of levodopa, dopamine agonists

• May increase the effects of antihypertensive drugs

• May enhance QTc prolongation of other drugs capable of prolonging QTc interval

• Additive effects may occur if used with CNS depressants

• Respiratory depression or respiratory arrest may occur if mesoridazine is used with a barbiturate

• Some patients taking a neuroleptic and lithium have developed an encephalopathic syndrome similar to neuroleptic malignant syndrome

• Combined use with epinephrine may lower blood pressure