Friday, April 12, 2013

Current TB Drugs Could Lead to Drug Anti-Resistance In A Small Number Of Cases; Finding Is Based On Mathematical Modeling & Not Field Results

TB Policies & Procedures

An article, by Amy Maxmen, in Nature News says that Tb drugs that contain isoniazid as an aactive ingredient might lead to isoniazid-resistance in some individuals, although it must be clearly stated that this finding is based on mathematical modelling, and not on actual field results.

Maxmen writes:
A study published today in Science Translational Medicine illustrates the perverse choice that public health experts sometimes must make between preventing a disease and preserving the effectiveness of a treatment. When it comes to tuberculosis, the report finds that prophylaxis comes with a higher cost than previously recognized.
The main ingredient in the drug cocktail to cure tuberculosis, isoniazid, can also protect people from contracting the disease in the first place. This second function is particularly important for those with fragile immune systems who frequently acquire and die from tuberculosis. In sub-Saharan Africa, tuberculosis is the leading cause of death among HIV-infected individuals. To curb this fate, the World Health Organization(WHO) recommends isoniazid as a preventative therapy for HIV-positive patients that don’t already show signs of active tuberculosis.
However, according to new study, led by Harriet Mills at the University of Bristol, in communities that implement isoniazid preventative therapy (IPT) the incidence of new isoniazid-resistant cases per year will double in the next 40 years.The typical TB treatment that includes isoniazid lasts six months. But when isoniazid cannot be used, a patient has to endure a longer treatment, which includes injections and swallowing a dozen tablets daily for two years. These drugs have side effects such as seizures and permanent hearing loss.
TB is proving a difficult disease to treat, although this latest finding was achieved through mathematical modelling and not actual field results; this is important to note. There are, however, two therapies in the drug pipeline that use what are called combination therapies, which do not include isoniazid

In an earlier article ("TB drugs chalk up rare win"), Maxmen writes:
The new combination therapy consists of PA-824, a novel drug in the TB pipeline; moxifloxacin, an antibiotic for treating pneumonia and sinus infections; and pyrazinamide, a TB drug developed in 1952. During a two-week trial, the combination eliminated more than 99% of M. tuberculosis in patients’ sputum. It promises to be far less taxing for patients than the current regimen for drug-resistant TB, which entails injections and two years of swallowing as many as 20 tablets a day with side effects that can include vomiting, seizures, painful nerve damage and permanent hearing loss.

You can read the rest of the article at [Nature News]