If p-aminosalicylic acid and rifampicin are both included in the treatment regimen, they should be given not less than eight hours apart to ensure satisfactory blood levels.

Interference with laboratory and diagnostic tests

Therapeutic levels of rifampicin have been shown to inhibit standard microbiological assays for serum folate and Vitamin B12. Thus alternative assay methods should be considered. Transient elevation of BSP and serum bilirubin has been reported. Rifampicin may impair biliary excretion of contrast media used for visualization of the gallbladder, due to competition for biliary excretion. Therefore, these tests should be performed before the morning dose of rifampicin.
4.6 Pregnancy and lactation
Pregnancy

At very high doses in animals rifampicin has been shown to have teratogenic effects. There are no well controlled studies with rifampicin in pregnant women. Although rifampicin has been reported to cross the placental barrier and appear in cord blood, the effect of rifampicin, alone or in combination with other antituberculosis drugs, on the human foetus is not known. Therefore, Rifadin should be used in pregnant women or in women of child bearing potential only if the potential benefit justifies the potential risk to the foetus. When Rifadin is administered during the last few weeks of pregnancy it may cause post-natal haemorrhages in the mother and infant for which treatment with Vitamin K1 may be indicated.

Lactation

Rifampicin is excreted in breast milk, patients receiving rifampicin should not breast feed unless in the physician's judgement the potential benefit to the patient outweighs the potential risk to the infant.
4.7 Effects on ability to drive and use machines
None stated
4.8 Undesirable effects
The following CIOMS frequency rating is used, when applicable:

Very common ≥ 10 %; Common ≥ 1 and <10%; Uncommon ≥ 0.1 and <1%;

Rare ≥ 0.01 and <0.1%; Very rare <0.01%, Unknown (cannot be estimated from available data).

Reactions occurring with either daily or intermittent dosage regimens include:

Infections and infestations

Unknown: Pseudomembranous colitis, influenza consisting of episodes of pyrexia, chills, headache, dizziness

Blood and lymphatic system disorders

Common: Thrombocytopenia with or without purpura, usually associated with intermittent therapy, but is reversible if drug is discontinued as soon as purpura occurs.

Uncommon: leukopenia

Unknown: Disseminated intravascular coagulation,eosinophilia, agranulocytosis, hemolytic anemia

Immune system disorders

Unknown: anaphylactic reaction

Endocrine disorders

Unknown: adrenal insufficiency in patients with compromised adrenal function have been observed.

Metabolism and nutritional disorders

Unknown: decreased appetite

Psychiatric disorders

Unknown: Psychotic disorder

Nervous system disorders

Unknown: Cerebral hemorrhage and fatalities have been reported when rifampicin administration has been continued or resumed after the appearance of purpura.

Eye disorders

Unknown: Tear discoloration

Vascul