PYRIMETHAMINE (Systemic)

Some commonly used brand names are:

In the U.S.?

• Daraprim

In Canada?

• Daraprim

Category

• Antiprotozoal

Description

Pyrimethamine (peer-i-METH-a-meen) is an antiprotozoal ((AN-tee-proe-toe-ZOE-al)) medicine. Antiprotozoals work by killing protozoa (tiny, one-celled animals)or preventing their growth. Some protozoa are parasites that can cause manydifferent kinds of infections in the body.

This medicine is used with one or more other medicines to treat and preventmalaria and to treat toxoplasmosis ((tok-soe-plaz-MOE-sis)). This medicine may also be used forother problems as determined by your doctor.

Pyrimethamine is available only with your doctor's prescription, in thefollowing dosage form:

Oral
• Tablets (U.S. and Canada)

Before Using This Medicine

In deciding to use a medicine,the risks of taking the medicine must be weighed against the good it willdo. This is a decision you and your doctor will make. For pyrimethamine, thefollowing should be considered:

Allergies?Tell your doctor if you have ever had any unusual orallergic reaction to pyrimethamine. Also tell your health care professionalif you are allergic to any other substances, such as foods, preservatives,or dyes.

Pregnancy?Pyrimethamine has not been studied in pregnant women.However, studies in animals have shown that pyrimethamine causes birth defectssuch as cleft palate, brachygnathia (abnormal shortness of the jaw bone),oligodactyly (fewer than 5 digits on a hand or foot), microphthalmia (abnormalsmallness of the eye). Before taking this medicine, make sure your doctorknows if you are pregnant or if you may become pregnant.

Breast-feeding?Pyrimethamine passes into breast milk. However,problems in nursing babies have not been reported. Mothers who are takingthis medicine and who wish to breast-feed should discuss this with their doctor.

Children?Pyrimethamine has been used in children and, in effectivedoses, has not been shown to cause different side effects or problems in childrenthan it does in adults.

Older adults?Many medicines have not been studied specificallyin older people. Therefore, it may not be known whether they work exactlythe same way they do in younger adults or if they cause different side effectsor problems in older people. There is no specific information comparing useof pyrimethamine in the elderly with use in other age groups.

Other medicines?Although certain medicines should not be usedtogether at all, in other cases two different medicines may be used togethereven if an interaction might occur. In these cases, your doctor may want tochange the dose, or other precautions may be necessary. When you are takingpyrimethamine, it is especially important that your health care professionalknow if you are taking any of the following:

• Amphotericin B by injection (e.g., Fungizone) or
• Antineoplastics (cancer medicine) or
• Antithyroid agents (medicine for overactive thyroid) or
• Azathioprine (e.g., Imuran) or
• Chloramphenicol (e.g., Chloromycetin) or
• Colchicine or
• Cyclophosphamide (e.g., Cytoxan) or
• Flucytosine (e.g., Ancobon) or
• Ganciclovir (e.g., Cytovene) or
• Interferon (e.g., Intron A, Roferon-A) or
• Mercaptopurine (e.g., Purinethol) or
• Methotrexate (e.g., Mexate) or
• Plicamycin (e.g., Mithracin) or
• Zidovudine (e.g., AZT, Retrovir)?Use of these medicines togetherwith pyrimethamine may increase the chance of side effects affecting the blood

• Bone marrow suppressants (methotrexate [e.g., Rheumatrex], proguanil[e.g., Malarone], sulfonamides [medicines used to treat infections], trimethoprim-sulfamethoxazole[e.g., Bactrim], zidovudine [e.g., Retrovir])?may increase risk of bonemarrow problems

• Lorazepam (e.g., Ativan)?Mild liver problems have been reportedwhen using this medicine together with pyrimethamine

• Phenytoin (e.g., Dilantin)?Use of this medicine together withpyrimethamine may affect folate (vitamin B) levels in the body

Other medical problems?The presence of other medicalproblems may affect the use of pyrimethamine. Make sure you tell your doctorif you have any other medical problems, especially:

• Allergy to pyrimethamine or any ingredient in the medicine?pyrimethamineshould not be used

• Anemia or other blood problems?High doses of pyrimethaminemay make these conditions worse

• Kidney problems or
• Liver problems or
• Lack of vitamin B in the body caused by
  • Alcoholism (drinking too much alcohol) or
  • Malabsorption syndrome (when a person's body does not absorb enoughnutrients from the food they eat)
  ?May make the condition worse

• Seizure disorders, such as epilepsy?High doses of pyrimethaminemay increase the chance of convulsions (seizures)

Proper Use of This Medicine

Keep this medicine out of the reach of children. Overdose is especiallydangerous in children.

If this medicine upsets your stomach or causes vomiting, it may be takenwith meals or a snack.

If you are taking this medicine to treat malaria,take the number of tablets your doctor told you to take (up to 3) once, asa single dose, along with other medicine your doctor gave you. If you developa fever and are not near a medical facility, and are taking this medicineto treat what you think may possibly be malaria, take the number of tabletsyour doctor told you to take (up to 3) once, as a single dose.

This medicine works best when you take it on a regular schedule. If youare to take two doses a day, one dose may be taken with breakfast and theother one with the evening meal. Make sure that you donot miss any doses. If you have any questions about this, check withyour health care professional.

Dosing?The dose of pyrimethamine will be differentfor different patients. Follow your doctor's orders orthe directions on the label. The following information includes onlythe average doses of pyrimethamine. If your dose is different,do not change it unless your doctor tells you to do so.

The number of doses you take each day, the time allowedbetween doses, and the length of time you take the medicine depend on themedical problem for which you are taking pyrimethamine.

• For the treatment of malaria:
  • Adults and adolescents: 25 milligrams of pyrimethamine daily togetherwith a sulfonamide for 2 days. These two medicines may also be taken withother medicine. This will be determined by your doctor.
  • Children: Dose is based on body weight and will be determined bythe doctor. Pyrimethamine may be taken together with other medicines.
• For the treatment of toxoplasmosis:
  • Adults and adolescents: Starting dose if 50 to 75 milligrams of pyrimethaminedaily taken together with other medicines for several weeks. After one tothree weeks, your doctor may lower your dose. The proper dose for you mustbe determined by the doctor.
  • Children: Dose is based on body weight and must be determined bythe doctor.
• For the prevention of malaria:
  • Adults and adolescents: 25 milligrams taken once a week.
  • Children: Dose is based on age and must be determined by the doctor.

Missed dose?If you do miss a dose of this medicine, take itas soon as possible. This will help you to keep taking your medicine on aregular schedule. However, if it is almost time for your next dose, skip themissed dose and go back to your regular dosing schedule. Do not double doses.

Storage?To store this medicine:

• Keep out of the reach of children. Overdose is very dangerous.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in otherdamp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be surethat any discarded medicine is out of the reach of children.

Precautions While Using This Medicine

It is very important that your doctor check you at regular visits for any blood problems that may be caused by this medicine, especiallyif you will be taking this medicine in high doses for toxoplasmosis.

If your symptoms do not improve within a few days or if they become worse,check with your doctor.

If this medicine causes anemia, your doctor may want you to take leucovorin(e.g., folinic acid, Wellcovorin) to help clear up the anemia. If so, it isimportant to take the leucovorin every day while you are taking this medicine.Do not miss any doses.

Pyrimethamine, especially in high doses, may cause blood problems. Theseproblems may result in a greater chance of certain infections, slow healing,and bleeding of the gums. Therefore, you should be careful when using regulartoothbrushes, dental floss, and toothpicks. Dental work should be delayeduntil your blood counts have returned to normal. Check with your medical doctoror dentist if you have any questions about proper oral hygiene (mouth care)during treatment.

Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects.Although not all of these side effects may occur, if they do occur they mayneed medical attention.

Check with your doctor immediately if any ofthe following side effects occur:

Less common

Black, tarry stools; blood in urineor stools; cough or hoarseness; fever or chills; irritation or soreness of tongue; lower back or side pain; painful or difficult urination; pinpoint red spotson skin; unusual bleeding or bruising

Rare

Bleeding or crusting sores on lips; chest pain or discomfort; muscle cramps or pain; redness, blistering, peeling, or loosening of skin; skin rash; sores, ulcers, and/or whitespots in mouth; sore throat; unusual tiredness or weakness

Frequency not known

Blood in urine; diarrhea; difficulty swallowing; dizziness; fainting spells; fast, slow, or irregularheartbeat; hives; itching; joint or muscle pain; lightheadedness; pale skin; pounding or rapid pulse; puffiness or swelling ofthe eyelids or around the eyes, face, lips or tongue; rapid breathing; red, irritated eyes; red skin lesions, often with a purple center; shortness of breath; swollen glands; tightness in chest; unexplained bleedingor bruising; wheezing

Symptoms of overdose

Abdominal or stomach pain; convulsions(seizures); increased excitability; vomiting (severe and continuing)

Other side effects may occurthat usually do not need medical attention. These side effects may go awayduring treatment as your body adjusts to the medicine. However, check withyour doctor if any of the following side effects continue or are bothersome:

Less common

Diarrhea; loss of appetite; nausea; vomiting

Other side effects not listed above may also occur insome patients. If you notice any other effects, check with your doctor.

Additional Information

Once a medicine has been approvedfor marketing for a certain use, experience may show that it is also usefulfor other medical problems. Although these uses are not included in productlabeling, pyrimethamine is used in certain patients with the following medicalconditions:

• Isosporiasis (treatment and prevention)
• Pneumocystis carinii pneumonia (treatment)

For patients taking this medicine for Pneumocystis cariniipneumonia:

• Pyrimethamine is used in combination with other medicines for mildto moderate pneumonia in patients who cannot take standard treatment.

Other than the above information, there is no additional information relatingto proper use, precautions, or side effects for these uses.