Resources for Health Professionals

Treatment

For cutaneous symptoms of Gnathostoma infection, both albendazole and ivermectin have been shown to result in cure in several trials that were too small to firmly establish efficacy and safety of treatment.

Reported cure rates at 6 months after treatment with albendazole are >90% and after treatment with ivermectin range from 76–95.2%. Albendazole may cause outward migration of larvae. Ivermectin may cause a temporary increase of cutaneous symptoms. Two small studies in which patients were followed up for 1 year or longer found cure rates after treatment with albendazole decreased over time. Relapse is not uncommon, however, with either treatment and has been shown to occur up to 26 months after initial therapy. Monitoring for symptom recurrence is needed for all patients regardless of treatment regimen. Relapse does not necessarily require treatment with a different medication, though data on this issue also are limited.

Two different regimens of albendazole (400 mg daily for 21 days and 400 mg twice daily for 21 days) and two different regimens of ivermectin (200 mcg/kg once daily for 1 day and 200 mcg/kg once daily for 2 days) have been studied. Data are insufficient to determine which regimen is the most effective, so it would probably be prudent to use the higher dose regimen of either medication until better data are available.

Whether to treat ocular and central nervous system (CNS) Gnathostoma infection remains controversial, particularly as there are no published studies of the efficacy of albendazole or ivermectin. As albendazole may cause larvae to migrate and ivermectin may cause a disease flare, there is concern that treatment with antihelminthics could worsen a patient’s neurologic status and possibly increase the risk for death or permanent neurologic deficit. There has been only one observational study of corticosteroids in patients presenting with probable Gnathostoma infection. No benefit of corticosteroids was demonstrated, possibly because it is thought that much of the damage to the CNS is caused by mechanical destruction of tissue.

At this time it is not possible to give recommendations for the treatment of CNS or ocular disease other than to provide supportive care. As gnathostomiasis has been shown to cause intracranial hemorrhage, patients with neurologic disease should be carefully monitored and plans for prompt intervention should be put into place.

Albendazole

Albendazole is pregnancy category C. Data on the use of albendazole in pregnant women are limited, though the available evidence suggests no difference in congenital abnormalities in the children of women who were accidentally treated with albendazole during mass prevention campaigns compared with those who were not. In mass prevention campaigns for which the World Health Organization (WHO) has determined that the benefit of treatment outweighs the risk, WHO allows use of albendazole in the 2nd and 3rd trimesters of pregnancy. However, the risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

It is not known whether albendazole is excreted in human milk. Albendazole should be used with caution in breastfeeding women.

The safety of albendazole in children less than 6 years old is not certain. Studies of the use of albendazole in children as young as one year old suggest that its use is safe. According to WHO guidelines for mass prevention campaigns, albendazole can be used in children as young as 1 year old. Many children less than 6 years old have been treated in these campaigns with albendazole, albeit at a reduced dose.

Ivermectin

Ivermectin is pregnancy category C. Data on the use of ivermectin in pregnant women are limited, though the available evidence suggests no difference in congenital abnormalities in the children of women who were accidentally treated during mass prevention campaigns with ivermectin compared with those who were not. The World Health Organization (WHO) excludes pregnant women from mass prevention campaigns that use ivermectin. However, the risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Ivermectin is excreted in low concentrations in human milk. Ivermectin should be used in breast-feeding women only when the risk to the infant is outweighed by the risk of disease progress in the mother in the absence of treatment.

The safety of ivermectin in children who weigh less than 15kg has not been demonstrated. According to the WHO guidelines for mass prevention campaigns, children who are at least 90 cm tall can be treated safely with ivermectin. The WHO growth standard curves show that this height is reached by 50% of boys by the time they are 28 months old and by 50% of girls by the time they are 30 months old, many children less than 3 years old been safely treated with ivermectin in mass prevention campaigns, albeit at a reduced dose.