What is the dose of Diethylcarbamazine (DEC) for the treatment of lymphatic filariasis?

DEC Dosing for Lymphatic Filariasis

For lymphatic filariasis treatment, administer diethylcarbamazine (DEC) 6 mg/kg orally in 3 divided doses daily for 14 days, combined with doxycycline 200 mg daily for 6 weeks. 1

Critical Pre-Treatment Requirements

Before initiating DEC therapy, you must exclude co-infections that can cause life-threatening complications:

• Screen for onchocerciasis using skin snips for microscopy and slit lamp examination, as DEC can cause severe reactions including blindness, hypotension, pruritus, and erythema in co-infected patients 2

• Screen for loiasis using daytime blood microscopy (10 am to 2 pm) with 20 ml citrated blood samples, as DEC can cause fatal encephalopathy in patients with high Loa loa microfilarial loads (>1000/ml) 3, 4

• If either co-infection is present, seek expert consultation immediately before proceeding with any treatment 1

Standard Treatment Regimen

The recommended approach for confirmed lymphatic filariasis without co-infections:

• DEC 6 mg/kg/day divided into 3 doses for 14 days (e.g., for a 70 kg patient: approximately 140 mg three times daily) 1

• Plus doxycycline 200 mg once daily for 6 weeks started concurrently with DEC 1, 3

• This combination targets both microfilariae (DEC) and the Wolbachia endosymbiont bacteria essential for adult worm survival (doxycycline) 3

Alternative Regimen for Co-Endemic Areas

In regions where onchocerciasis is co-endemic and DEC is contraindicated:

• Ivermectin 200 μg/kg as a single dose plus albendazole 400 mg as a single dose 3, 2

• This regimen avoids the severe adverse reactions DEC can cause in onchocerciasis patients 2

Special Loiasis Dosing Protocol

For patients with confirmed loiasis, DEC dosing requires a graduated escalation approach:

If microfilariae >1000/ml:

• First treat with prednisolone (after screening for strongyloidiasis) and albendazole 200 mg twice daily for 21 days to reduce microfilarial load 1, 4
• Check blood microscopy at day 28 and repeat albendazole until microfilarial count drops below 1000/ml 1
• Then proceed with DEC using graduated dosing with prednisolone cover 1

If microfilariae <1000/ml or negative:

• Day 1: 50 mg single dose 1, 4
• Day 2: 50 mg three times daily 1, 4
• Day 3: 100 mg three times daily 1, 4
• Day 4 onwards: 200 mg three times daily for 21 days 1, 4

Monitoring Requirements

• Monitor for adverse reactions including fever, lymphadenitis, and lymphangitis during treatment, which typically occur 12-24 hours after drug administration and resolve within 2-4 days 3, 5

• Full blood counts and liver function tests every 2 weeks for 3 months, then monthly if within normal range for prolonged courses 3

• Follow-up blood microscopy at 6 and 12 months after last negative sample to monitor for relapse 1, 4

Special Populations

• Pregnancy: Avoid DEC and seek expert consultation; ivermectin can be used in second and third trimesters if necessary 3, 2

• Breastfeeding: Ivermectin is excreted in very low levels in breast milk and is likely compatible 3, 2

• Children 12-24 months: Discuss with expert before treatment 3, 2

• Children >24 months: Standard dosing can be used 3, 2

Important Clinical Pearls

• DEC should be taken with food as bioavailability increases significantly 2

• Avoid alcohol during treatment as it may worsen side effects 3

• Prednisolone is usually given alongside DEC when microfilaraemia is present to reduce inflammatory reactions 2

• The multi-dose 14-day regimen is significantly more effective than single-dose therapy, achieving 99.6% reduction in microfilariae versus 85.7% with single-dose treatment 6