Naphthalene and paradichlorobenzene are common ingredients in diaper pail and toilet bowl deodorizers and moth repellents. Both compounds have a similar pungent odor and are clear-to-white crystalline substances; therefore, they are difficult to distinguish visually. Naphthalene, 10% in oil, was used as a scabicide in the past. Naphthalene is no longer commonly used because it largely has been replaced by the less toxic paradichlorobenzene.
Mechanism of toxicity. Both compounds cause GI upset, and both may cause CNS stimulation. In addition, naphthalene may produce hemolysis, especially in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency.
Naphthalene. As little as one mothball containing naphthalene (250–500 mg) may produce hemolysis in a patient with G6PD deficiency. The amount necessary to produce lethargy or seizures is not known but may be as little as 1–2 g (four to eight mothballs). Several infants developed serious poisoning from clothes and bedding that had been stored in naphthalene mothballs.
Paradichlorobenzene is much less toxic than naphthalene; up to 20-g ingestions have been well tolerated in adults. The oral 50% lethal dose (LD50) for paradichlorobenzene in rats is 2.5–3.2 g/kg.
Pharmacokinetics. Both compounds are rapidly absorbed orally or by inhalation.
Clinical presentation. Acute ingestion usually causes prompt nausea and vomiting. Both compounds are volatile, and inhalation of vapors may cause eye, nose, and throat irritation.
Naphthalene. Agitation, lethargy, and seizures may occur with naphthalene ingestion. Acute hemolysis may occur, especially in patients with G6PD deficiency. Chronic inhalation has also caused hemolytic anemia.
Paradichlorobenzene acute ingestions are virtually always innocuous. Serious poisoning in animals is reported to cause tremors and hepatic necrosis. Paradichlorobenzene decomposes to hydrochloric acid; this may explain some of its irritant effects. Chronic ingestion of paradichlorobenzene (as mothballs or toilet freshener blocks) has been reported to cause ataxia and encephalopathy.
Diagnosis usually is based on a history of ingestion and the characteristic “mothball” smell around the mouth and in the vomitus. Differentiation between naphthalene and paradichlorobenzene by odor or color is difficult. In an in vitro x-ray study, paradichlorobenzene was radiopaque but naphthalene was not visible. In a saturated salt solution (about 1 tablespoon of salt in 4 oz of water), naphthalene will float and paradichlorobenzene will sink.
Specific levels. Serum levels are not available.
Other useful laboratory studies include CBC and, if hemolysis is suspected, haptoglobin, free hemoglobin, and urine dipstick for occult blood (positive with hemoglobinuria).
Emergency and supportive measures
Maintain an open airway and assist ventilation if necessary (See Airway and Breathing).
Treat coma (See Coma and stupor) and seizures (See Seizures) if they occur.
Treat hemolysis and resulting hemoglobinuria, if they occur, by intravenous hydration and urinary alkalinization (see “Rhabdomyolysis”).
Specific drugs and antidotes. There is no specific antidote.
Decontamination (See Decontamination)
Naphthalene. Administer activated charcoal orally if conditions are appropriate (see Table I–38). Gastric lavage is not necessary after small to moderate ingestions if activated charcoal can be given. Do not induce vomiting because of ...