Daraprim (pyrimethamine) is actually an anti-parasitic drug, used to treat Toxoplasmosis and Malaria. People with weakened immune systems – not just those with AIDS – but also,  chemotherapy patients, organ transplant recipients, people taking corticosteroids, and infants in utero cannot effectively fight off the parasite that causes Toxoplasmosis. However, people with AIDS are the most afflicted by this disease; 10 percent of AIDS related deaths are due to Toxoplasmosis.

One-third of humanity is said to have been infected with the parasite, but healthy people rarely get sick from it. Babies in utero are susceptible if the mother is infected, for the first time, during pregnancy.

Daraprim itself DOES NOT fight the virus that causes AIDS. It fights one of the opportunistic diseases that is a consequence of having an impaired immune system. It is used both prophylactically and as a treatment in person with AIDS.  Once exposed to the parasite, the body mounts an immunologic defense, but the parasite remains dormant within cysts in organ tissues of the body. If for any reason, your immune system is compromised, the illness may take hold again.

Toxoplasmosis

Toxoplasmosis is caused by the  protozoan parasite Toxoplasma gondii. Like other protozoa we have discussed, it exists in various forms or stages: oocyte, tachyzoite, and cysts (bradyzoite).

Cats and Toxoplasmosis

Members of the cat family are the definitive hosts of T gondii. The parasite replicates inside the intestines of cats , and sheds as oocytes in their feces. Insects(flies, roaches, beetles) and earth worms come in contact with the feces and can spread the parasite; cats also bury their feces in soil. This accounts for its persistence in the environment. Cats must be infected with the parasite in order to spread it. To avoid infection, domestic cats should be fed only store-bought cat food or cooked food. Don’t allow your cat to eat mice or  birds.

Human and Toxoplasmosis

People become infected with T gondii  through eating undercooked meat, primarily pork and lamb, or from ingesting food/water contaminated by infected cat feces. Primary infection in healthy persons is usually asymptomatic, and rarely requires any treatment. However, swelling of the lymph nodes along the base of the head and throat, eye infection consisting of inflammation of the choroid and necrosis of the retina, are possible. Others signs and symptoms include fever, fatigue, muscle pain, sore throat, and headache.

Infants. T gondii can cross the placenta and infect the fetus, causing blindness (retinochoroiditis) or mental retardation (hydrocephalus/cerebral calcification/convulsions).

AIDS & Immunosuppressed. Toxoplasmosis in the immunocompromised are a result of re-activation of previous infection. T gondii in these people affects the Central Nervous System (CNS), causing toxoplasmic encephalitis. Other outcomes can be retinochoroiditis, toxoplasma pneumonia and respiratory failure, and abnormalities of the blood similar to septic shock.

Pyrimethamine (Daraprim)

Pyrimethamine is an antifolate drug that inhibits the enzyme responsible for folinic acid production in parasite. Folate plays an important role in the synthesis and repair of DNA. The toxicity of pyrimethamine is a result of its partial activity on mammalian cells as well, it can also deplete dihydrofoalte reductase in humans, for this reason it is given in combination with folic acid. It’s slow action allows it to be use prophylactically, but as a treatment it must be used in combination with a sulfonaminde or clindamycin (antimicrobials). Trimethoprim is an alternative to pyrimethamine and is less toxic, but pyrimethamine  is the hallmark treatment. At present, there is no vaccine available.

Prevention

After handling raw meat,  hands, cutting boards, and surfaces should be washed. Avoid tasting meat while seasoning and cooking. Consumption of undercooked meat should be avoided, especially by pregnant women. Pregnant women should also avoid cleaning cat litter. Since T gondii can persist in soil for years, wearing gloves while gardening is wise, as well as, washing all fruits and vegetables thoroughly. The parasite is killed by soap and water, extreme heat, and extreme cold.

Toxoplasmosis can be life threatening to people whose immune systems are deficient from disease, such as AIDS, or suppressed from chemotherapy  and immunosuppressive drug (prevent organ/tissue rejection after transplantation). The reason why the recent  increase in the price of Daraprim is important to AIDS patients, is that they are significantly most at risk, and therapy consists of both treatment and secondary prophylaxis; which can span the course of 6 weeks or longer.