Malathion

CAS RN: 121-75-5

Laboratory

A) LOTION - At the time of this review, systemic effects have not been reported with normal therapeutic use of 0.5% malathion lotion. Laboratory evaluation is generally not necessary, unless patients manifest signs and symptoms of cholinergic excess.
B) Monitor vital signs frequently. Institute continuous cardiac and pulse oximetry monitoring. Monitor for respiratory distress (i.e. bronchorrhea, bronchospasm) and for clinical evidence of cholinergic excess (i.e. salivation, vomiting, urination, defecation, miosis).
C) Determine plasma and/or red blood cell cholinesterase activities (plasma is generally more sensitive, but red cell correlates somewhat better with clinical signs and symptoms). Depression in excess of 50% of baseline is generally associated with cholinergic effects, in severe poisoning cholinesterase activity may be depressed by 90% of baseline. Correlation between cholinesterase levels and clinical effects in milder poisonings may be poor.
D) Obtain serial ECGs. Patients who develop a prolonged QTc interval or PVCs are more likely to develop respiratory insufficiency and have a worse prognosis.
E) Monitor electrolytes and serum lipase in patients with significant poisoning. Patients who have increased pancreatic enzyme concentrations are more likely to develop respiratory insufficiency and have a worse prognosis.
F) Monitor pulmonary function (i.e. forced vital capacity, expiratory volume in 1 second, negative inspiratory force) in symptomatic patients, may help anticipate need for intubation.
G) Isopropyl alcohol is contained in high concentrations in malathion lotions used in the treatment of head lice.
1) Obtain a metabolic panel, serum isopropyl alcohol and acetone concentrations. Ketonemia and ketonuria may present within 1 to 3 hours of ingestion, but acidosis is NOT expected. Isopropanol elevates measured serum osmolality. Refer to ISOPROPYL ALCOHOL document for further information.
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