Anthelmintic Agents

Pregnancy risk categories: Table 1 in Antimicrobial Agents.

1. Benzimidazoles: Albendazole, mebendazole, triclabendazole:

1) Spectrum of activity:

a) Albendazole: Albendazole has a broad range of activity against intestinal roundworms (Ascaris lumbricoides, Enterobius vermicularis, Trichuris trichiura, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis), extraintestinal roundworms (cutaneous larva migrans, Trichinella spp, Loa loa), tapeworms (Echinococcus spp, Taenia solium cysticerci), and flatworms (Clonorchis sinensis). It is also used as alternative therapy for Giardia lamblia infection.

b) Mebendazole: Mebendazole shows similar activity to albendazole but is used predominantly in the treatment of intestinal nematodes, paragonimiasis, and cutaneous larva migrans.

c) Triclabendazole: The drug of choice for the treatment of liver fluke infections due to Fasciola hepatica.

2) Adverse effects: Hypersensitivity reaction. Hematologic effects, such as bone marrow suppression (anemia, leukopenia, pancytopenia). Hepatic effects, such as reversible transaminase elevations. Gastrointestinal effects, such as abdominal pain, nausea, and vomiting. Alopecia (albendazole).

3) Pregnancy risk: C.

2. Diethylcarbamazine:

1) Spectrum of activity: Diethylcarbamazine has activity against lymphatic filariasis, loiasis, and visceral larva migrans.

2) Adverse reactions: Inflammatory reaction (Mazzotti reaction) secondary to death of adult worms (fever, urticaria, asthma, gastrointestinal upset). Other adverse effects include headache, dizziness, and transient exacerbation of lymphangitis. Contraindicated in patients with onchocerciasis because of the risk of blindness, severe exacerbation of skin disease, or both.

3) Pregnancy risk: Safety not established.

3. Ivermectin:

1) Spectrum of activity: Ivermectin is considered first-line therapy for the treatment of Strongyloides stercoralis and Onchocerca volvulus. It has activity against intestinal nematodes (A lumbricoides, E vermicularis, Trichuris trichiura) but albendazole is usually used as the first-line therapy. Ivermectin is also used in the treatment of cutaneous larva migrans and ectoparasitic infections, such as head lice and scabies. Ivermectin has poor efficacy against hookworms (A duodenale, N americanus).

2) Adverse reactions: Hypersensitivity reaction. Inflammatory reactions related to death of adult worms (Mazzotti reaction). Loiasis must be excluded before initiating treatment for onchocerciasis as serious and/or fatal encephalopathy has been reported with ivermectin use in coinfected patients.

3) Pregnancy risk: C.

4. Niclosamide:

1) Spectrum of activity: Niclosamide is an alternative treatment option for tapeworms, as it has activity against Taenia spp, Hymenolepis spp, and Diphyllobothrium spp. It is also active against flukes (flatworms), including C sinensis, F hepatica, Fasciolopsis buski, and Paragonimus spp.

2) Adverse reactions: Anorexia and/or nausea and vomiting.

3) Pregnancy risk: B.

5. Praziquantel:

1) Spectrum of activity: Praziquantel is considered first-line therapy for infections secondary to flukes (Schistosoma spp, Clonorchis, Paragonimus, and F buski) and intestinal tapeworms (Taenia spp [including cysticerci], Hymenolepis spp, and Diphyllobothrium spp). It is not active against F hepatica.

2) Adverse reactions: Mild adverse effects include drowsiness, nausea/vomiting, rash, and fever. Contraindicated in ocular cysticercosis.

3) Pregnancy risk: B.

6. Pyrantel:

1) Spectrum of activity: Pyrantel is active against intestinal roundworms (A lumbricoides, E vermicularis) and hookworms (A duodenale, N americanus). Pyrantel is often considered as alternative therapy for the infections listed above and is the drug of choice for pregnant women, as it has minimal systemic absorption.

2) Adverse reactions: Mild adverse effects, including gastrointestinal upset, nausea/vomiting, rash, and fever.

3) Pregnancy risk: C.