Mebendazole (MBZ) is a medication used to treat a number of parasitic worm infestations. This includes ascariasis, pinworm disease, hookworm infections, guinea worm infections, hydatid disease, and giardia, among others. It is taken by mouth. Mebendazole is usually well tolerated. Common side effects include headache, vomiting, and ringing in the ears. If used at large doses it may cause bone marrow suppression. It is unclear if it is safe in pregnancy. Mebendazole is a broad-spectrum antihelminthic agent of the benzimidazole type. Mebendazole came into use in 1971. It is included in the WHO Model List of Essential Medicines, the most important medications needed in a basic health system. Mebendazole is available as a generic medication. The wholesale cost in the developing world is between 0.004 and 0.04 USD per dose. In the United States a single dose is about 18 USD.