Tolerance of single high-dose ivermectin for treatment of lymphatic filariasis

Adverse events following single dose treatment of lymphatic filariasis: Observations from a review of the literature

Background

WHO’s Global Programme to Eliminate Lymphatic Filariasis (LF) uses mass drug administration (MDA) of anthelmintic medications to interrupt LF transmission in endemic areas. Recently, a single dose combination of ivermectin (IVM), diethylcarbamazine (DEC), and albendazole (ALB) was shown to be markedly more effective than the standard two-drug regimens (DEC or IVM, plus ALB) for achieving long-term clearance of microfilaremia.

Objective and methods

To provide context for the results of a large-scale, international safety trial of MDA using triple drug therapy, we searched Ovid Medline for studies published from 1985–2017 that reported adverse events (AEs) following treatment of LF with IVM, DEC, ALB, or any combination of these medications. Studies that reported AE rates by treatment group were included.

Findings

We reviewed 162 published manuscripts, 55 of which met inclusion criteria. Among these, 34 were clinic or hospital-based clinical trials, and 21 were community-based studies. Reported AE rates varied widely. The median AE rate following DEC or IVM treatment was greater than 60% among microfilaremic participants and less than 10% in persons without microfilaremia. The most common AEs reported were fever, headache, myalgia or arthralgia, fatigue, and malaise.

Interpretation

Mild to moderate systemic AEs related to death of microfilariae are common following LF treatment. Post-treatment AEs are transient and rarely severe or serious. Comparison of AE rates from different community studies is difficult due to inconsistent AE reporting, varied infection rates, and varied intensity of follow-up. A more uniform approach for assessing and reporting AEs in LF community treatment studies would be helpful.

WHO’s Global Programme to Eliminate Lymphatic Filariais (LF) supports annual mass drug administration to over 400 million people in LF-endemic areas each year. Two drug combinations (either DEC or ivermectin, given with albendazole) have been recommended in most endemic areas. With the exception of well-described serious adverse events (AEs) occurring in patients with high level loiasis, severe AEs due to these medications are extremely rare. Mild to moderate AEs, however, are common, particularly in patients with active filarial infection. In this manuscript we synthesize published data on AEs following single-dose treatment of LF with ivermectin, DEC, or albendazole. This provides a background against which to compare the safety of triple drug therapy (ivermectin, DEC, and albendazole) recently endorsed by WHO, and provides a useful context for evaluating safety of new treatments for LF. The compiled data illustrate that transient, mild to moderate AEs following single-dose LF treatment are common in microfilaremic patients and are much less common in amicrofilaremic patients. They also show that passive surveillance for post-treatment AEs underestimates AE incidence and suggest that adherence to common reporting standards would improve the usefulness of AE reporting in filariasis studies.

Translating Research into Reality: Elimination of Lymphatic Filariasis from Haiti

Research provides the essential foundation of disease elimination programs, including the global program to eliminate lymphatic filariasis (GPELF). The development and validation of new diagnostic tools and intervention strategies, critical steps in the evolution of GPELF, required a global effort. Lymphatic filariasis research in Haiti involved many partners and was directly linked to the development of the national elimination program and to the success achieved to date. Ongoing research efforts involving many partners will continue to be important in resolving the challenges faced by the program today in its final efforts to achieve elimination.

Control of bancroftian filariasis in an endemic area of Polynesia by ivermectin 400 micrograms/kg

Community treatment with ivermectin was implemented in Opoa, French Polynesia from April 1991 to October 1993. All consenting inhabitants aged 3 years or more were treated with twice-yearly single doses of ivermectin, pregnant women excepted. A dosage of 100 microgram/kg was used for the 3 first treatments and then abandoned because it did not reduce the prevalence of microfilariae (mf) carriers. With a dosage of 400 micrograms/kg dosage, this prevalence decreased dramatically from 21% to 7%, and the mf level in carriers dropped to only 0.5% of its initial value after 3 treatments. The 400 micrograms/kg dosage was well tolerated and compliance was excellent. The twice-yearly single dose strategy with ivermectin at 400 micrograms/kg is safe and highly effective for filariasis control in an endemic area.

Ivermectin dosing based on physical appearance

Ivermectin is a safe and effective microfilaricide which has been shown to have a beneficial impact on some onchocercal eye lesions. Current requirements for the distribution of ivermectin are that patients be weighed, and that their dose be determined according to their weight. This requirement increases the cost of distributing the drug to communities in need of treatment and, when scales breakdown, may lead to the suspension of distribution. Data are presented on a simple, alternative method of dose assessment based on the physical appearance of the patient. Fifteen assessors achieved an overall level of agreement with the weight-based schedule of 86% on a sample of 6420 patients. The level of agreement varied between assessors, from 73% to 95%. About 6% of the population would have received doses outside the range of the current weight-based schedule. We believe that the current insistence that each individual's dose of ivermectin be determined by weighing will hamper efforts to distribute the drug to those most in need of it and that our data indicate that workers can be trained to distribute ivermectin safely without weighing every individual. We would welcome confirmation of our findings from other populations.

Ivermectin levels in human breastmilk

Ivermectin levels were measured in breastmilk and plasma of 4 healthy mothers after an oral 150 micrograms/kg dose. Mean +/- S.D. plasma and milk values were 37.9 +/- 0.54 and 14.13 +/- 0.43 (ng/ml) respectively. Steady-state ivermectin levels in milk were low. Our results suggest that exclusion of lactating mothers from mass chemotherapy with ivermectin may be unnecessary.

Side reactions following ivermectin therapy in high density bancroftian microfilaraemics

Side reactions following ivermectin treatment were evaluated in sixty males with high density bancroftian microfilaremia (GM 1388/ml). Following a single oral dose of ivermectin of different strengths (20, 50, 100 or 200 micrograms/kg), microfilariae clearance and side reactions were monitored in a double blind fashion. Microfilaria levels fell rapidly after ivermectin administration in all dosage groups and 98% of pretreatment microfilariae was cleared after 12 h of treatment. The rate of microfilaria (mf) clearance was slower with 20 micrograms/kg than with the highest dose (200 micrograms/kg) administered. Forty-six patients (77%) became amicrofilaraemic within 2 weeks of treatment. Side reactions were noted in 97% of cases. The most common reactions were fever, headache, weakness, myalgia and cough which appeared by 12 h and subsided by 72 h following treatment. The frequency and intensity of side reactions were related to pretreatment mf densities and were independent of the dose administered. Unusual side reactions were noted in a few patients with high density microfilaraemia. These included intense cough, shortness of breath, blood tinged mucoid expectoration associated with patchy pneumonitis of the lung. Itchy rashes, lymphatic nodules and raised alkaline phosphatase level were also observed in some patients. These side reactions were transient, self limiting and were not serious enough to warrant any treatment. These exaggerated unusual reactions were possibly due to allergic response of the susceptible host to rapid killing of large number of microfilariae.

Treatment failure of a single high dose of ivermectin for Mansonella perstans filariasis

Infections with Mansonella perstans are common in certain parts of Africa and South America. There is no standard treatment at present. We evaluated the effect of a single high dose of ivermectin (600 micrograms/kg) on microfilaraemia in 7 consecutive patients. No decrease in microfilarial counts could be demonstrated after a follow-up period of 7-56 d.

Long-term suppression of microfilaraemia following ivermectin treatment

Lymphatic filariasis has been difficult to control until recently because of the lack of a suitable drug for treatment. Ivermectin has proven safe and effective at reducing levels of circulating microfilariae. However, the apparent need to administer the drug every 6 to 9 months to keep microfilaraemia levels sufficiently suppressed to reduce transmission has been a major drawback to using ivermectin in community-based intervention programmes. In a study conducted in Haiti, we have found that high doses of ivermectin suppress microfilaraemia levels for 2 years. Our findings suggest that a single dose of ivermectin can reduce transmission of lymphatic filariasis for extended periods of time, thus eliminating the need for costly biannual treatment.