MYCOBUTIN Capsules contain the antimycobacterial agent rifabutin, which is a semisynthetic ansamycin antibiotic derived from rifamycin S. MYCOBUTIN (rifabutin) Capsules for oral administration contain 150 mg of rifabutin, USP, per capsule, along with the inactive ingredients microcrystalline cellulose, magnesium stearate, red iron oxide, silica gel, sodium lauryl sulfate, titanium dioxide, and edible white ink.

The chemical name for rifabutin is 1',4-didehydro-1-deoxy-1,4-dihydro-5'-(2-methylpropyl)-1-oxorifamycin XIV (Chemical Abstracts Service, 9th Collective Index) or (9S, 12E, 14S, 15R, 16S, 17R, 18R, 19R, 20S, 21S, 22E, 24Z)-6,16,18,20-tetrahydroxy-1'-isobutyl-14-methoxy-7,9,15,17,19,21,25-heptamethyl-spiro [9,4-(epoxypentadeca[1,11,13]trienimino)-2H-furo[2',3':7,8]naphth[1,2-d]imidazole-2,4'-piperidine]-5,10,26-(3H,9H)-trione-16-acetate. Rifabutin has a molecular formula of C₄₆H₆₂N₄O₁₁, a molecular weight of 847.02 and the following structure:

Rifabutin is a red-violet powder soluble in chloroform and methanol, sparingly soluble in ethanol, and very slightly soluble in water (0.19 mg/mL). Its log P value (the base 10 logarithm of the partition coefficient between n-octanol and water) is 3.2 (n-octanol/water).

This medication may cause urine, sweat, saliva, or tears to turn brown-orange. This effect is harmless and will disappear when the medication is stopped. However, dentures and contact lenses may be permanently stained.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these rare but serious side effects occur: easy bleeding/bruising, signs of a new infection (such as fever, persistent sore throat/cough), muscle weakness/pain, joint pain/swelling, eye pain/redness, vision problems, chest pain/pressure, persistent nausea/vomiting, unusual weakness/tiredness, dark urine, yellowing eyes/skin.

This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to a type of resistant bacteria. This condition may occur during treatment or weeks to months after treatment has stopped. Do not use anti-diarrhea products or narcotic pain medications if you have any of the following symptoms because these products may make them worse. Tell your doctor immediately if you develop: persistent diarrhea, abdominal or stomach pain/cramping, blood/mucus in your stool.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking rifabutin, tell your doctor or pharmacist if you are allergic to it; or to other rifamycins (such as rifampin); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: kidney disease, liver disease, a certain blood disorder (porphyria).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Rifabutin may cause live bacterial vaccines (such as typhoid vaccine) not to work as well. Therefore, do not have any immunizations/vaccinations while using this medication without the consent of your doctor.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this medication passes into breast milk. Discuss the risks and benefits with your doctor before breast-feeding. If you have HIV disease, do not breast-feed because breast milk can transmit HIV.