Pyrimethamine is a prescription indicated for the treatment of serious parasite infection of the body, eye, or brain. This is to prevent toxoplasmosis infection in people with HIV infection. HIV infection is a chronic and potentially life-threatening condition. By damaging your immune system, it interferes with your body’s ability to fight the organisms that cause disease. Toxoplasmosis is a disease that results from infection with the toxoplasma gondii parasite. Infection usually occurs by eating undercooked contaminated meat or mother-to-child transmission during pregnancy. Most healthy people who are infected with toxoplasma have no signs and symptoms. For some, however, develop signs and symptoms similar to those of the flu including:

• Swollen lymph nodes
• Body aches
• Fever
• Headache
• Fatigue

In people with HIV infection, you may develop more severe signs and symptoms of:

• Confusion
• Headache
• Seizures
• Poor coordination
• Lung problems that may resemble tuberculosis or pneumocystis jiroveci pneumonia (a common opportunistic infection that is in people with AIDS)
• Blurred vision caused by severe inflammation of your retina

This medication may also be used to treat malaria. It is a disease caused by a parasite. The parasite is transmitted to humans through the bites of infected mosquitoes. People who have malaria usually feel very sick with a high fever and shaking chills. Malaria infection is generally characterized by the following signs and symptoms:

• Chills
• Fever
• Headache
• Muscle pain and fatigue
• Nausea and vomiting
• Chest or abdominal pain
• Sweating
• Cough

Pyrimethamine is an antiparasitic prescription approved by the U.S. Food and Drug Administration (FDA).  This is also a type of drug known as an antiprotozoal. This is mainly used with sulfonamide antibiotics to treat the condition. This medication helps kill the parasites. These are an organism that lives on or in a host organism and gets its food from or at the expense of its host. Pyrimethamine is supplied as tablets for oral administration. Each tablet is available in a 25 mg dosage form with Pyrimethamine as an active ingredient.

How does Pyrimethamine work?

Pyrimethamine stops the parasite from reproducing once it is in the bloodstream. It does this by blocking the action of a compound that is found in the parasite. This compound is an enzyme called dihydrofolate reductase that is involved in the reproduction of the parasite. Dihydrofolate reductase usually converts folic acid into folinic acid in the parasite. Wherein, it is a step essential for the parasite to produce new genetic material which is the DNA. New DNA is needed for the parasite to reproduce. By blocking its production, Pyrimethamine prevents the parasites from reproducing and increase in number.

In malaria which is caused by various types of parasites known as plasmodium, this drug may also work. Plasmodium is carried by mosquitoes and is injected into the bloodstream during a bite from an infected mosquito. This medication stops malaria parasites from increasing in numbers once in the blood.

Pyrimethamine is well absorbed with peak levels occurring between 2 to 6 hours following administration. It is eliminated slowly and has a plasma half-life approximately 96 hours.

How to use Pyrimethamine?

The recommended dosage is based on your medical condition, age, and response to the treatment. Your doctor may direct you to start at a lower dose and eventually increase it. You should take the right dose, not more or less. Remember to take it at the same time and in the same way each day. Do not suddenly stop taking this medication without the consent of your doctor. It may cause another complication or may worsen your current condition. For the best benefit from this product, take it regularly.

Pyrimethamine is to be taken by mouth. This is usually taken once or twice daily or as directed by your doctor. You may take each dose with a meal to lessen nausea and vomiting. If vomiting is severe or continues, your doctor may lower your dose or direct you to stop taking this drug. Swallow the tablet as a whole with a full glass of water. Do not break, chew, or crush it. If you missed a dose, take it as soon as you remember it. If it is almost time for your next dose, skip the missed dose and continue your regular dosing schedule. Do not double the dose to make up for the missed dose. Let your doctor know if your condition does not improve or if it gets worse.

What are the side effects of Pyrimethamine?

Common side effects:

• Vomiting
• Loss of appetite

Stop using Pyrimethamine and call your doctor right away if these occur:

• Swelling in your tongue
• Sore throat
• Easy bruising
• Pale skin or purple spots under your skin
• The first sign of any skin rash no matter how mild
• Blood in your urine
• Cold or flu symptoms
• Fever
• Trouble breathing
• New or worsening cough
• Irregular heartbeats
• Signs of folate deficiency (mood changes, unusual tiredness, mouth sores, or stomach discomfort)
• Severe skin reaction (skin pain, fever, burning in your eyes, causes blistering and peeling, or swelling in your face or tongue)

Call for medical assistance if you have allergic reaction signs such as:

• Hives
• Difficulty breathing
• Swelling of your tongue, throat, face, or lips

Warnings and Precautions

• Pyrimethamine can sometimes cause a decrease in the normal amounts of blood cells in the blood. For this reason, you may need to have blood tests every week while having this treatment.
• This medication should be used with caution in elderly people, those with decreased kidney or liver function, with anemia, or with a history of seizures.
• This is not recommended for use in the first three months of pregnancy.
• The drug should be used if you are allergic to one or any of its ingredients. Inform your doctor if you have previously experienced such an allergy.
• If you are breastfeeding women, consult your doctor first before using any medicine.
• Drink plenty of fluids while having this medication. It is to prevent kidney problems if you are taking a sulfa medication with Pyrimethamine.
• Do not share this or any of your medications with others even if they have the same symptoms as yours.