Questions and answers for people with TB or at risk of getting TB

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Questions and answers about TB treatment

1. I am taking TB medicines. My urine or tears have turned orange. Is this a problem?

This is common and almost always harmless. It is a side-effect of one of your TB medicines called rifampicin.

2. What are the differences between rifapentine, rifabutin and rifampicin and when would you use which?

All three drugs are in the same class. They are rifamycins.

Rifampicin (also called rifampin in the United States) has been more widely studied than either rifapentine and rifabutin. It is likely the most powerful TB drug available as it is able to kill slowly replicating and rapidly replicating bacteria. There has been quite a bit of recent work done on rifapentine by the US CDC in collaboration with the makers of rifapentine, Sanofi-Aventis. A few years ago, this company decided to restart their TB program and have been pursuing rifapentine in place of rifampicin. Rifapentine is not licensed for use in Europe and many other countries. In the US it is used in the intensive phase but not in HIV-positive people due to lack of data.

A recent study showed that 12 weeks of once-weekly rifapentine/isoniazid was as good as 9 months of daily isoniazid in treating latent TB. Based on this study the US is changing their guidelines. They are still collecting data for HIV-positive people and children so the guideline changes will only apply to HIV-negative adults. And this regimen has only been tested in low burden settings. One of the advantages of rifapentine over rifampicin is that rifapentine has a long half-life, allowing for intermittent dosing, and has been shown to have superior bactericidal activity to rifampicin and rifabutin.

No difference has been found between the efficacy of rifapentine and rifampicin when used as part of standard first-line TB treatment.

Rifabutin is the only rifamycin that does not appear to have a significant impact on the p450 enzyme and therefore is receommended for use with antiretrovirals but it has not been well studied and the dosages for adults and children are not well understood. Also it is a much more expensive drug than rifampicin.

(Thank you to Claire Wingfield for providing most of this answer.)

3. What is the difference between rifampicin and rifampin

There is no difference. They are the scientific same for the same drug. Rifampin is the name more commonly used in the United States, while rifampicin is more commonly used in Europe and South Africa.

4. How long do I have to take TB medicines?

If this is the first time you are being treated for TB and you do not have drug-resistant TB, then treatment is usually 6 months. But there are variations on this in different parts of the world.

The first two months are called the intensive phase. During this phase you will usually take four drugs, hopefully in one pill. The drugs you will be given are likely to be isoniazid (or simply INH), rifampicin, pyrazinamide and ethambutol. Again, there might be different treatment regimens in your part of the world.

The next four months are called the continuation phase. During this phase you will take just isoniazid and rifampicin, hopefully still in one pill.

If this is the second time you are being treated for TB, you might also have to take daily injections of streptomycin and your treatment might by eight months instead of six. Also the continuation phase might be longer.

If you have been diagnosed with multi-drug resistant (MDR) or extensively drug resistant (XDR) TB, the treatment regimen you will receive will be more complex and possibly even tailored for your individual needs. Treatment for MDR and XDR TB is usually about two years.

Questions and answers about diagnosing TB

1. Why are HIV-positive people with TB often smear-negative?

People who are coinfected with TB and HIV are up to 24–61 percent more likely to have smear-negative TB than are HIV-negative people. Up to 61% of people coinfected with HIV and TB generate smear-negative tests – in other words, an incorrect diagnosis.

Simple explanation

TB is expelled into the sputum when TB-infected cells are killed. In immune compromised people, fewer TB cells are killed by the immune system, so less TB gets into the sputum.

Technical explanation

As CD4 T cells are lost due to and compromised by HIV infection, CD8 T cells lose the directional support they need to do their job of killing TB-infected cells because they are no longer being told to kill TB-infected cells. TB is expelled into the sputum when TB-infected cells are killed. Therefore, the chance of smear-negative TB increases because fewer TB bacilli are released in the sputum. This means that TB is not being released into the sputum, so despite the fact that someone may have TB in his or her system it is not detected using sputum-smear microscopy.

Questions and answers about TB prevention

1. What is isoniazid preventative therapy (IPT)?

This is when a person, usually HIV-positive, takes a drug called isoniazid to reduce the risk of getting TB. IPT has been shown to only benefit people who are tuberculin skin test positive.

2. I am HIV-positive and I work in a prison or hospital where many people are ill with TB. Should I take isoniazid preventative therapy (IPT)?

First you should have something called a tuberculin skin test. If this test is positive, then you should consider taking isoniazid preventative therapy.

Studies show that taking isoniazid reduces the risk of you becoming ill with TB.