Along with its needed effects, rifampin may cause some unwanted or undesirable effects. Rifampin is generally well tolerated in most people. The frequency and severity of unwanted effects depend on many factors including dose, age of the person, existing health problems and individual response. Possible unwanted effects include:

• appetite loss
• nausea
• stomach ache
• dizziness
• drowsiness
• rash
• itching
• flushing
• headache
• gas
• tiredness
• reddish-orange discoloration of bodily fluids (e.g. sweat,tears, etc.)

Uncommon:

• vomiting
• diarrhea
• menstrual irregularities
• confusion
• jaundice (yellowing of skin and eyes)

Rare:

• muscle weakness
• shortness of breath, wheezing
• visual disturbances

If you are (or suspect you are) experiencing any unwanted effects, report them to your doctor or pharmacist.

Rifampin is an antituberculosis drug that can be either bactericidal (kill bacteria) or bacteriostatic (inhibit bacterial growth), depending on the concentration of the drug in the body. It is thought to inhibit certain pathways that are needed for the bacteria to grow.

Rifampin may turn sweat, tears, sputum, feces, urine and saliva a red-orange color but this is not harmful. Soft contact lenses should not be worn during rifampin therapy as they may become permanently stained.
The effectiveness of oral contraceptives cannot be relied upon while on rifampin therapy. It is recommended that alternative or additional methods of birth control be used.
Drug interactions: It is important to tell your doctor and pharmacist about any prescription or over-the-counter medications you are taking to help avoid any serious drug interactions. The dose of one or both medications may need to be altered or a new drug may be prescribed. In some cases, one of the drugs may have to be discontinued. The following drugs and drug classes have been known to interact with rifampin.

• blood thinners (e.g. warfarin)
• benzodiazepines (e.g. diazepam)
• barbiturates (e.g. phenobarbital)
• hydantoins (e.g. phenytoin)
• beta-blockers (e.g. propranolol)
• ketoconazole
• oral contreceptives (e.g. Triphasil®)
• corticosteroids (e.g. prednisone)
• cyclosporine (e.g. Neoral®)
• digoxin (e.g. Lanoxin®)
• disopyramide (e.g. Rythmodan®)
• enalapril (e.g. Vasotec®)
• estrogens (e.g. Premarin®)
• methadone
• quinidine
• sulfonylureas (e.g. tolbutamide)
• theophylline (e.g. Theo-Dur®)
• verapamil (e.g. Isoptin®)
• antacids

Use is not recommended in the following situations:

• jaundice (yellowing of the skin and eyes)
• allergy to rifampin or any other rifamycin

Caution is recommended in the following situations:

• liver disease

Use in pregnancy: Rifampin is the drug of choice in pregnancy.  Contact your doctor if you suspect you may be pregnant.
Use while breastfeeding: Rifampin passes into breast-milk in small amounts. Contact your doctor or pharmacist before use.