Mesoridazine

Intramuscular
Resistant schizophrenia, Severe schizophrenia

Oral
Resistant schizophrenia, Severe schizophrenia

Oral:
Dilute oral concentrate just prior to admin with distilled water, acidified tap water, orange or grape juice. Do not prepare and store bulk dilutions.

Oral:
Do not mix oral solutions of mesoridazine and lithium.

Severe CNS depression and coma; prolonged QT interval (>450 msec), including congenital prolongation; history of arrhythmias. Lactation.

Admin to patients only if baseline QTc <450 msec. Discontinue if QTc interval >500 msec. Monitor potassium levels. CNS depression; Parkinson's disease; haemodynamic instability; bone marrow suppression; predisposition to seizures; subcortical brain damage; severe cardiac, hepatic, renal or respiratory disease; patients at risk of pneumonia (e.g. Alzheimer's disease); breast cancer or other prolactin-dependent tumours. May alter temperature regulation or mask toxicity of other drugs. Patients at risk of orthostatic hypotension; cerebrovascular disease, CVD. Decreased GI motility, urinary retention, benign prostatic hyperplasia, xerostomia or visual problems. Narrow-angle glaucoma and myasthenia gravis. Pregnancy.

Hypotension, orthostatic hypotension, tachycardia, cardiac arrhythmias, sinus tachycardia; sedation, drowsiness, restlessness, anxiety, extrapyramidal symptoms, pseudoparkinsonian signs, tardive dyskinesia, neuroleptic malignant syndrome, seizures, altered central temperature regulation, akathisia, dystonias, dizziness, hyperthermia; hypersensitivity reactions; amenorrhoea, galactorrhoea, gynaecomastia, syndrome of inappropriate antidiuretic hormone; GI upset, xerostomia, constipation, wt gain; urinary retention, impotence; agranulocytosis, leukopenia, thrombocytopenia, haemolysis, eosinophilia; cholestatic jaundice; trismus; retinal pigmentation, nystagmus, blurred vision; nasal congestion; decreased diaphoresis, SLE.

Symptoms: Involuntary muscle movements, haematological disturbances (e.g. agranulocytosis, leukopenia), arrhythmias, coma, deep sleep, ejaculatory disturbances, enuresis, extrapyramidal reaction, galactorrhoea, gynaecomastia, hypotension, impotence, neuroleptic malignant syndrome, nystagmus, Parkinson's-like symptoms, photophobia, priapism, QRS prolongation, urine discolouration, vision colour changes. Management: Activated charcoal or gastric lavage within 1 hr. Supportive therapy. Multiple dosing of activated charcoal may be useful; not dialysable.

Increased risk of extrapyramidal symptoms (EPS) with central acetylcholinesterase inhibitors. Reduced absorption with aluminium salts. Reduced efficacy of amphetamines; increased risk of psychotic symptoms with amphetamines. Reduced efficacy or excess anticholinergic effects with anticholinergics. Additive hypotensive effects with antihypertensives, trazodone. May inhibit effects of bromocriptine on serum prolactin levels. Additive sedative effects with CNS depressants. May diminish effects of epinephrine. May inhibit the antiparkinsonian effect of levodopa. May increase risk of EPS with metoclopramide. Increased risk of neurotoxicity with lithium (rare). Increased serum levels with sulfadoxime-pyrimethamine. Increased toxicity or altered response with TCAs. May increase serum levels of valproic acid.
Potentially Fatal: Increased risk of malignant arrhythmias with other QTc-prolonging agents.

May cause false-positive results when testing for TCAs through the EMIT system.

Description:
Mechanism of Action: Mesoridazine is a phenothiazine antipsychotic. It has a piperidine side-chain and is a metabolite of thioridazine. It acts by blocking postsynaptic CNS dopamine receptors.
Onset: 30 min to 1 hr.
Duration: 4-6 hr.
Pharmacokinetics:
Absorption: Tablet: Erratic; Liquid: More dependable. Peak serum concentrations in 2-4 hr.
Distribution: Widely distributed into body including breast milk. Protein-binding: 91-99%.
Metabolism: Hepatic.
Excretion: Mainly via urine; 24-48 hr (elimination half-life).

Intramuscular:
Store at 25°C (77°F).
Oral:
Tablet: Store at 25°C (77°F). Oral solution: Store below 25°C (77°F); protect from light.

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