OVIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for OVIDE (OVIDE).
OVIDE (malathion) is an organophosphate insecticide that irreversibly inhibits acetylcholinesterase, leading to accumulation of acetylcholine at synapses, resulting in paralysis and death of lice. It also has pediculicidal and ovicidal activity.
| Metabolism | Malathion is metabolized primarily in the liver by carboxylesterases to malaoxon, which is more potent; further hydrolysis to inactive metabolites. Cytochrome P450 enzymes play a minor role. |
| Excretion | Primarily renal elimination of metabolites; <1% excreted unchanged in urine. Biliary/fecal excretion accounts for <5%. |
| Half-life | Terminal elimination half-life is approximately 8–10 hours in adults; prolonged in hepatic impairment. |
| Protein binding | ≥90% bound to serum proteins, primarily albumin. |
| Volume of Distribution | Vd is approximately 3–4 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Bioavailability after topical application is minimal (≤5%) due to low percutaneous absorption. |
| Onset of Action | Following topical application, clinical effect on lice and nits is observed within 10–15 minutes; pediculicidal activity is rapid. |
| Duration of Action | A single application provides ovicidal activity for up to 7 days; residual action is limited. |
Apply OVIDE (malathion 0.5% lotion) topically to dry hair and scalp, leave for 8-12 hours, then rinse thoroughly. Repeat in 7-9 days if live lice persist.
| Dosage form | LOTION |
| Renal impairment | No dosage adjustment required for renal impairment as systemic absorption is minimal (<1%). |
| Liver impairment | No dosage adjustment required for hepatic impairment as systemic absorption is minimal (<1%). |
| Pediatric use | For infants and children aged ≥2 years: apply same dose as adults. For children <2 years: safety and efficacy not established; use only under physician supervision. |
| Geriatric use | No specific geriatric dose adjustment; use same adult dosing regimen. Caution with concomitant skin conditions or polypharmacy. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for OVIDE (OVIDE).
| Breastfeeding | Malathion is excreted into breast milk in small amounts after topical application; however, the milk-to-plasma ratio is not established due to minimal systemic absorption. The American Academy of Pediatrics considers malathion compatible with breastfeeding. Avoid application to breast area to prevent infant ingestion. Caution in preterm or low-birth-weight infants. |
| Teratogenic Risk | OVIDE (malathion lotion 0.5%) is FDA Pregnancy Category B. Animal studies have not demonstrated fetal harm, but there are no adequate and well-controlled studies in pregnant women. The drug is absorbed minimally through the skin; however, as a precaution, avoid use in pregnancy unless clearly needed. First trimester: theoretical risk due to organogenesis; second and third trimesters: low risk based on limited human data. No specific malformation pattern reported. |
■ FDA Black Box Warning
No FDA black box warning exists for OVIDE.
| Serious Effects |
["Hypersensitivity to malathion or any component of the formulation.","Premature infants (because of increased skin permeability and risk of toxicity).","Known history of cholinesterase deficiency."]
| Precautions | ["Flammable: Avoid heat, open flame, or smoking during and immediately after application.","Accidental ingestion may cause severe organophosphate toxicity; seek medical attention immediately.","Use with caution in patients with seizures disorders or with prior hypersensitivity to organophosphates.","Avoid contact with eyes (irritation) and mucous membranes.","Do not use for re-treatment within 1 week due to residual ovicidal activity."] |
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| Fetal Monitoring | No specific maternal or fetal monitoring required beyond routine prenatal care. Monitor for local skin reactions. If accidental ingestion occurs, monitor for cholinergic symptoms (e.g., salivation, lacrimation, urination, defecation, GI upset, emesis). In case of extensive use or damaged skin, consider serum cholinesterase levels. |
| Fertility Effects | No adverse effects on fertility reported in animal studies. Human data are lacking. Topical malathion is unlikely to impair fertility due to minimal systemic absorption. No known impact on spermatogenesis or ovulatory function. |