Ivermectin is an anthelminthic drug with a broad spectrum of action and is prepared from the compounds obtained from Streptomyces avermitilis called avermectins. It is the only orally available drug for in ectoparasite infections such as scabies and pediculosis. Ivermectin is also an effective anti-nematodal agent with activity against Ascaris lumbricoides and Strongyloides stercoralis. It is however, used as a second line agent in these conditions or as a combination with other anthelminthic drugs like albendazole and mebendazole. It is also effective in filariasis and onchocerciasis caused by the parasites Wuchereria bancrofti and Loa loa, respectively.
How Ivermectin Works: Ivermectin, when administered, acts on the glutamate gated chloride channels in invertebrates. This action of Ivermectin results in tonic paralysis of the nematode worm. The worm is unable to move or feed and dies due to starvation. Ivermectin has also been found to act on GABA receptors in the nematode worms, facilitating GABA mediated neurotransmission. These actions result in Ivermectin being lethal to nematodes like Ascaris lumbricoides, Strongyloides stercoralis and other parasites like Wuchereria bancrofti and Loa loa. Ivermectin also has a cidal (killing) action on ectoparasites like scabies and head and body lice (pediculosis).
How To Take Ivermectin: Ivermectin is indicated for the treatment of intestinal strongyloidosis, i.e. infection with Strongyloides stercoralis limited to the intestinal tract. In this condition it is used as a drug of first choice. Ivermectin is also effective against Ascaris lumbricoides and is a second line drug in this infestation. It is commonly used in combination with albendazole in the treatment of ascariasis. Ivermectin is used as a drug of first choice in onchocerciasis, also known as ‘river blindness’, as it does not lead to severe allergic reactions to the end products of the dead worm as that seen after treatment with diethylcarbazine (DEC). Ivermectin is the only orally active and effective scabicidal agent which is also used in the treatment of pediculosis (lice infestation). Ivermectin is supplied as oral tablets of 3 mg strength. For the treatment of strongyloidosis, Ivermectin is given in dosages as per body weight of the individual. For an average adult with 60 kg body weight, a dose of 12 mg is to be administered, i.e. 4 tablets of Ivermectin. To calculate the required dosage, 0.15-0.2 mg/kg body weight is to be used. Generally a single oral dose of Ivermectin is sufficient for desired anti-parasitic action. Ascariasis and filariasis can be treated with a combination of albendazole 400 mg dose and Ivermectin 10-15 mg given once a year for 5-6 years. This gives good results and keeps the patient nematode-free. Onchocerciasis is treated with a single dose of Ivermectin of 0.15 mg/kg with average adult dose for a 60 kg body weight individual coming to 9 mg or 3 tablets taken together. For scabies and pediculosis, a single oral dose of 0.2 mg/kg is to be administered. This is approximately 4 tablets of Ivermectin for an adult person. The tablets are to be consumed at one time preferably before food.
Precautions And Side Effects Of Ivermectin: When patients of onchocerciasis are treated with Ivermectin, there is a possibility of developing the Mazzotti reaction, i.e. cutaneous and systemic allergic manifestations due to death of the worm. Rarely patients on Ivermectin may even develop other effects such as exacerbation (flaring up) of onchodermatitis which are skin reactions to the worm infestation; and encephalopathy which may be fatal. Commonly seen side effects of Ivermectin are asthenia, fatigue, abdominal pain, nausea, vomiting, diarrhoea, anorexia, dizziness, somnolence, vertigo and skin symptoms like rash, itching and urticaria. Rarer side effects of Ivermectin include severe cutaneous and systemic allergic reactions, worsening of dermatitis and encephalopathy.