Therapeutic Drug Monitoring and Estimation of Undernutrition among Adult Household Contacts of TB Patients on TB Preventive Treatment

TB preventive treatment (TPT) is an effective and cost-effective intervention to prevent progression from infection to disease and to reduce mortality due to TB.The TPT with isoniazid in countries like India currently covers only select groups of contacts like children under 6 years of age and people living with HIV. WHO recently made a conditional recommendation of offering TPT to all household contacts (HHC) i.e, any person residing in the same household as a TB patient of all ages. The burden of TB infection is the highest among household contacts. Apart from being the largest burden of cases and deaths related to tuberculosis, India also has undernutrition as leading risk factor accounting for TB incidence and, undernutrition is a major common risk factor for mortality in patients with TB in India. The relationship between TB and nutrition is bidirectional, i.e. having active TB leads to loss of weight, and being underweight is considered a risk factor for developing TB, whether through reactivation of latent TB or developing progressive primary disease upon infection. A systematic review of literature showed that across a variety of settings with different levels of TB burden, a strong and consistent log-linear relationship existed between BMI and TB incidence - for each unit reduction in BMI the risk of TB increased by about 14 per cent. Different pathophysiological conditions in undernutrition/malnutrition can alter the pharmacokinetics of drugs. Gastrointestinal changes include hypochlorhydria, delayed gastrointestinal emptying time, increased or decreased intestinal transit time, gastric and mucosal atrophy and dysfunction, gastrointestinal inflammation, and pancreatic insufficiency. In the enterocytes, P-glycoprotein activity is decreased and tight junctions are enlarged, influencing the uptake of nutrients and drugs. This pharmacokinetic variability is one of the main causes for sub-optimal therapeutic drug concentration. 

Hence Therapeutic drug monitoring is one of the best tools, to asses optimum drug concentration in such conditions. Undernourishment leads to various micro and micronutrition deficiency leading to alteration in the pharmacokinetic properties which in tent leads to decreased therapeutic efficacy of drug taken for TB preventive treatment.  As HHC are at high risk of developing the disease and importance of nutrition in TB is well established. It is important to estimate optimum drug therapy through Therapeutic drug monitoring and also estimate undernutrition among the adult household contacts of TB patients put on TB preventive treatment to prevent infection to disease progression.