Half of the world’s population are children, yet many of the most important developments in drug therapy ignore the needs of this most vulnerable population. With Mycobacterium tuberculosis as the cause of one of the most important chronic infectious diseases worldwide,¹ it is gratifying to see research that describes the integration of modern molecular techniques to improve the delivery of the most important component of tuberculosis treatment for the world’s children. The study by Schaaf and colleagues,² reported in this issue of the journal, focuses our attention on isoniazid therapy which is still the mainstay of tuberculosis therapy for both adults and children.

For most drugs, children need specific doses, usually defined in terms of body weight. Extrapolation of the dose from adult studies by body weight would result in the under-dosing of many drugs, as children are proportionally more efficient at clearing the drugs.³ Isoniazid is a good example. The study by Schaaf et al highlights the fact that not only are higher doses required in childhood to achieve the same levels as adults, but also that children are as metabolically heterogeneous as adults. Correct dosage is important to maximise the chances of effective treatment, and to minimise the chances of adverse effects, both serious and minor. Adherence in tuberculosis treatment of children is poor⁴ and may be improved by minimising adverse effects of therapy.

Where a drug is being used for the treatment of infections, the appropriate efficacious dose is defined by the characteristics of the organism as well as host factors such as absorption. Drug exposure must be adequate to control or eliminate the infection.^5,6 Adverse effects are host dependent and may be dose related or idiosyncratic. Many of …