Rifampin (Rifampicin) and Orange Urine

What rifampin does and why it changes urine colour

Rifampin (called rifampicin in the UK and most of Europe; rifampin is the US generic name) is a bactericidal antibiotic that inhibits bacterial DNA-dependent RNA polymerase. It is one of the most important antibiotics in the treatment of tuberculosis and is part of the standard four-drug combination regimen used for TB treatment in most countries. It is also used for chemoprophylaxis in close contacts of meningococcal disease and for some other difficult-to-treat infections. The CDC TB treatment reference and NHS TB treatment guidance cover the typical regimens.

Rifampin and its metabolites are intensely orange-red in colour. They are excreted in urine, sweat, tears, saliva, and faeces, producing a characteristic orange-red discolouration of all of these body fluids. This is described in detail in the BNF rifampicin entry and in patient information leaflets supplied with the medication. The discolouration is harmless. Patients are routinely warned about it before starting treatment so that they are not surprised.

The colour intensity correlates roughly with the dose and the time since the last dose. Urine is most intensely coloured several hours after a dose. The colour clears within hours of stopping; rifampin has a half-life of about 3 hours in adults, so most of the colour-producing metabolite is cleared within 24-48 hours of the last dose.

Standard regimens involving rifampin

Tuberculosis treatment (active TB): The standard regimen for drug-susceptible TB is a six-month course: rifampin plus isoniazid plus pyrazinamide plus ethambutol for the first two months, followed by rifampin plus isoniazid for the remaining four months. This regimen is recommended by the WHO, by the CDC, and by NICE. People taking this regimen will have orange urine for the entire six months.

Latent TB infection treatment: Several regimens exist, including rifampin alone for four months (often called 4R), or weekly rifapentine plus isoniazid for 12 weeks (3HP regimen). Both produce orange urine.

Meningococcal prophylaxis: Two days of rifampin given to close contacts of someone with meningococcal meningitis. Urine will be orange for about two days.

Other uses: Rifampin is sometimes added to other antibiotic regimens for severe or prosthetic joint or device-related staphylococcal infections, brucellosis, and certain mycobacterial infections beyond TB. Duration varies.

What else turns orange (and what does not)

All body fluids are affected: urine (the most noticeable), sweat (which may stain pale clothing), tears (which may stain soft contact lenses), saliva, and faeces. Skin can take on a faint orange tint in some people on prolonged treatment. Hair is not typically affected.

Soft contact lenses: Rifampin can permanently stain soft contact lenses orange-red. The BNF advises being aware of this. Daily disposable lenses are a workaround. Hard (rigid gas-permeable) lenses are not affected in the same way.

Tooth brushing and laundry: Saliva discolouration may produce orange staining of toothbrushes and pillowcases. Light-coloured fabrics worn next to skin during heavy sweating may stain. The colour washes out of cotton and most synthetic fabrics with normal laundering, although it may take a couple of washes.

Side effects beyond colour: when to act

The orange discolouration is harmless and expected. The serious side effects to watch for are separate. The BNF rifampicin entry lists the relevant adverse effects. The most important are:

• -Hepatotoxicity (liver toxicity): Yellow eyes or skin (jaundice), dark urine that is genuinely tea or coffee-coloured rather than the typical rifampin orange, pale stools, severe fatigue, loss of appetite, nausea, vomiting, right-upper-quadrant pain. Liver toxicity can be severe and warrants stopping the medication and urgent contact with your TB team or GP for liver function tests. The risk is higher with combination TB therapy and in people with pre-existing liver disease or heavy alcohol use.
• -Hypersensitivity reactions: Fever, rash, particularly with intermittent or restarted dosing. Severe forms include Stevens-Johnson syndrome and toxic epidermal necrolysis (rare). Any new fever or rash on rifampin warrants prompt clinical contact.
• -Thrombocytopenia (low platelets): Easy bruising, prolonged bleeding from cuts, petechial rash. Warrants urgent assessment.
• -Acute kidney injury: Reduced urine output, swelling, fatigue. Less common but recognised, particularly with intermittent dosing.

The TB treatment monitoring schedule typically includes baseline liver function tests, liver function repeat at 2 weeks then monthly, and any urgent repeats if symptoms develop. The NICE NG33 tuberculosis guideline covers the monitoring schedule.

Drug interactions: rifampin reduces other drug effects

Rifampin is one of the most potent inducers of cytochrome P450 enzymes (particularly CYP3A4) in clinical use. This means it speeds up the metabolism of many other drugs, reducing their effectiveness. The BNF rifampicin interactions reference lists hundreds of drugs whose levels are affected.

Notable interactions include:

• -Hormonal contraceptives: Rifampin substantially reduces effectiveness. The Faculty of Sexual and Reproductive Healthcare guidance recommends additional non-hormonal contraception (condoms or copper IUD) during treatment and for at least 28 days after stopping.
• -Warfarin: Rifampin substantially reduces anticoagulant effect; INR monitoring needed.
• -Direct oral anticoagulants (DOACs): Effectiveness reduced; combination usually avoided.
• -Many antiretrovirals (HIV medications): Major interactions; specialist input needed for co-treatment of HIV and TB.
• -Some immunosuppressants (ciclosporin, tacrolimus): Levels reduced.
• -Methadone: Withdrawal can be precipitated; dose adjustment usually needed.

Anyone starting rifampin should review their full medication list with the prescribing clinician or pharmacist for interaction checks.

Frequently asked questions