• Antiprotozoal, systemic

Benznidazole (benz-NYE-da-zole) belongs to a group of medicines called antiprotozoals. It is used to treat an infection called American trypanosomiasis (Chagas' disease). Benznidazole works by killing the protozoa (tiny, one-celled animals).

Benznidazole is available only with your doctor's prescription in the following dosage form:

Oral
• Tablets (Brazil)

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

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

Pregnancy—Studies have not been done in pregnant women. The World Health Organization (WHO) does not recommend the use of benznidazole during the first 3 months of pregnancy. However, this medicine has not been shown to cause birth defects or other problems in animal studies.

Breast-feeding—It is not known whether benznidazole passes into breast milk. Although most medicines pass into breast milk in small amounts, many of them may be used safely while breast-feeding. Mothers who are taking this medicine and who wish to breast-feed should discuss this with their doctor.

Children—Although there is no specific information comparing use of benznidazole in children with use in other age groups, this medicine is not expected to cause different side effects or problems in children than it does in adults.

Older adults—Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information comparing use of benznidazole in the elderly with use in other age groups.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking benznidazole, it is especially important that your health care professional know if you are taking any of the following:

• Alcohol—Taking alcohol with benznidazole may cause unwanted effects such as stomach cramps, nausea, vomiting, headache, or redness of face

• Inflammation or pain medicine, except narcotics, such as aspirin, or
• Anticoagulants (blood thinners), such as warfarin (e.g., Coumadin, Panwarfarin, Warfilone)—Taking aspirin or anticoagulants with benznidazole may increase the chance of bleeding

• Blood disease or
• Kidney disease or
• Liver disease—Patients with these conditions may have an increased chance of side effects

Take this medicine with meals, preferably after breakfast and after supper, to decrease the chance of stomach upset. If you get an upset stomach (diarrhea, nausea, stomach pain, or vomiting) and it continues, check with your doctor.

To help clear up your infection, take this medicine exactly as directed by your doctor for the full time of treatment.

Dosing—

The dose of benznidazole will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of benznidazole. If your dose is different, do not change it unless your doctor tells you to do so.

• For oral dosage form (tablets):
  • For Chagas' disease:
    • Adults and children 12 years of age and over—Dose is based on body weight and must be determined by your doctor. The usual dose is 5 to 7 milligrams (mg) per kilogram (kg) (2.2 to 3.1 mg per pound) of body weight per day. Treatment should continue for thirty to sixty days.
    • Children up to 12 years of age—Dose is based on body weight and must be determined by your doctor. The usual dose is 10 mg per kg (4.5 mg per pound) of body weight per day. Treatment should continue for thirty to sixty days.

Missed dose—

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed 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.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

It is important that your doctor check your progress at regular visits. This is to help make sure that the infection is cleared up completely.

If your symptoms become worse, check with your doctor .

Although rare, Benznidazole can lower the number of white blood cells in your blood, increasing your chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting.

• Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills.
• Check with your doctor immediately if you notice any unusual bleeding or bruising; black, tarry stools; blood in urine or stools; or pinpoint red spots on your skin.

Drinking alcoholic beverages while taking this medicine may cause stomach pain, nausea, vomiting, headache, flushing or redness of the face. Other alcohol-containing preparations (for example, elixirs, cough syrups, and tonics) may also cause problems. Therefore, do not drink alcoholic beverages or take other alcohol-containing preparations while you are taking benznidazole .

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 may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• More common
  • Convulsions (seizures);  numbness, tingling pain, or weakness in hands or feet;  reddish discoloration of skin 
  
  

• Rare
  • Fever or chills;  pinpoint red spots on skin;  skin rash;  sore throat;  unusual bleeding or bruising 
  
  

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

• More common
  • Abdominal or stomach pain;  diarrhea ;  nausea;  vomiting 
  
  

• Rare
  • Confusion;  dizziness;  headache;  restlessness;  temporary loss of memory;  trouble in sleeping;  difficulty concentrating;  unusual tiredness or weakness 
  
  

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