A team from National Institute for Research in Tuberculosis (NIRT) examined 25 TB patients in Chennai who consumed food just before they took their medication.They found significantly lower concentrations of anti-TB drugs and a delay in their absorption. They studied the concentrations of three key first-line drugs: rifampicin, isoniazid and pyrazinamide.
Dr Soumya Swaminathan, director general of Indian Council of Medical Researchand one of the co-authors of the study , said though most doctors are aware of the clinical impact of food on rifampicin, guidelines on when to take the other drugs are hazy .
“Our study shows that at least two other first-line drugs need to be taken on fasting,” she said, adding that the findings are significant as the dosage of first-line drugs is low.
But not everyone can tolerate these drugs on an empty stomach. “In such cases, a gap of at least three hours after food [is ideal],” she said.
The research, which was published in Indian Journal of Medical Research, involved studying patients who took their pills after breakfast. The same group was examined after a 12-hour over night fast, followed by drug administration and breakfast two hours later.
The researchers found drug administration with food caused the plasma concentration (time taken for drug to start taking effect after absorption in blood) to decrease by 50%, 45% and 34% for rifampicin, isoniazid and pyrazinamide, respectively.
Researchers say food intake exerts a complex influence on drug bioavailability .
“It may interfere not only with tablet disintegration, dissolving of drugs and drug transit through the gastrointestinal tract but may also affect metabolic transformation of drugs in the gastrointestinal wall and liver,” said Dr Geetha Ramachandran, of the department of biochemistry and clinical pharmacology at NIRT.
She said there is no clear guidance on whether or not to take anti-TB medication with food. “It is believed that drugs are not well tolerated on an empty stomach and many patients prefer to have food before they take medicines,” she said.