Karachi is facing a drugs epidemic. Pakistan's sprawling port city has an estimated half a million chronic heroin addicts. The drug is cheap and easily available as it comes across the Pakistan/Afghanistan border, before being shipped to Europe and the US. Mobeen Azhar finds out how a charity is trying to help addicts and their families.

An NGO called the Edhi Foundation operates what is thought to be the world's largest drug rehabilitation centre. It's here that Mobeen meets brothers Yusaf and Husein who have checked themselves in. Patients who volunteer for treatment like this can leave whenever they feel ready. But the majority of patients, like 24-year-old Saqandar, are brought in by their desperate relatives, and according to Edhi rules, only the family can decide when they will be released.

The centre offers heroin users food and painkillers to ease the physical symptoms of withdrawal - but conventional treatment like methadone is not available. So does enforced cold turkey really work?

Mobeen follows the stories of three heroin addicts and finds out how the stress of their addiction takes its toll on them and their families.

Presenter: Mobeen Azhar
Producer: Ben Crighton.