From the outside it appears like any other private medical clinic in Penang, though a little shabby. But a closer look reveals something unusual.

First, the 'patients' are predominantly male adults. Every few minutes one of them walks into the clinic, steps up to the counter and produces a card or booklet. Words are exchanged. The patient then walks into an adjoining room - and less than a minute later, walks out.

What happens inside the room is anyone's guess. But the managers of two drug rehabilitation drop-in centres told IPS that certain private general practitioners are dispensing legitimate drug substitutes and potentially dangerous - though also legitimate - substances to drug addicts a little too freely.