Tetramisole is a synthetic chemical compound that has found applications in various fields, particularly in medicine. This substance functions as a pharmaceutical agent, known for its specific biological activities.
What is Tetramisole?
Tetramisole is an imidazothiazole derivative and an anthelmintic drug. It is a white to pale cream crystalline powder with a bitter taste. It is readily soluble in water and methanol, slightly soluble in ethanol, and insoluble in acetone. Tetramisole is a racemic mixture of L- and D-isomers; the L-isomer, also called levamisole, is responsible for most of its biological activity.
How Tetramisole Works
It targets the nervous system of parasitic worms. It stimulates nicotinic acetylcholine receptors (nAChRs) on nematode body wall muscles. This continuous stimulation leads to a sustained contraction of the worm’s muscles. The paralyzed worms are then expelled from the body. This specific interaction with parasitic neuromuscular transmission is central to its therapeutic effects.
Its Main Applications
Tetramisole hydrochloride has been extensively used in veterinary medicine as a broad-spectrum anthelmintic since its introduction in 1967. It is effective against a range of nematode infections affecting livestock such as cattle, sheep, and swine, as well as poultry and dogs. The drug helps in the control and management of parasitic diseases, often administered orally or through injection depending on the animal and formulation. Its efficacy against both adult and larval stages of gastrointestinal, lung, heart, and kidney nematodes has made it a valuable tool in animal health.
In human medicine, tetramisole had historical uses for treating parasitic infections, including hookworm. However, its use in humans has largely declined due to the development and availability of safer alternative treatments. Beyond its anthelmintic properties, its L-isomer, levamisole, was also investigated for its immunomodulatory effects and was historically used in the treatment of certain cancers, such as colorectal cancer, and rheumatoid arthritis in some regions. Despite these past applications, it is no longer available for human use in many countries, including the United States.
Potential Side Effects and Safety
The use of tetramisole, particularly at higher doses, has been associated with various side effects and a specific toxicity profile. In animals, acute toxicity studies in mice showed symptoms like nervousness, crouching, piloerection, and tremor. The median lethal doses (LD50) in mice varied depending on the administration route, with oral administration having an LD50 of approximately 110 mg/kg, subcutaneous at 57 mg/kg, and intraperitoneal at 34 mg/kg. These observations suggest involvement of the nervous system in its acute toxicity.
Historically, in human use, especially at repeated high doses or for non-anthelmintic indications, levamisole (the L-isomer of tetramisole) was linked to severe adverse reactions. These included blood disorders such as agranulocytosis, a condition characterized by a severe reduction in a type of white blood cell, which impairs the body’s ability to fight infection. Other reported side effects in humans included psychiatric disorders, hepatobiliary issues, vasculitis, encephalopathy, and neuropathy. The potential for these serious reactions led to its restricted or discontinued use in human medicine in many regions. When administered in veterinary settings, adherence to recommended dosages and administration guidelines is important to minimize adverse reactions.