America has been fighting the War on Drugs for decades, but the drug cartels, the suppliers and the dealers appear to be always one step ahead of the authorities.

President Trump has declared the cartels, "terrorists" and labelled fentanyl, the powerful synthetic opioid, a "weapon of mass destruction".

But the drug supply is changing, with other deadly synthetics being added to the mix, including strong animal tranquillisers, known on the streets as "tranq".

While overdose deaths are falling, the potency of the new drugs has recovery workers worried. For some the answer might lie in reducing demand, giving users support and helping them end their addiction.

BBC international correspondent Quentin Sommerville and camera journalist Darren Conway travelled to Columbus, Ohio to find out more.

Read more on this story: A wave of homemade, synthetic drugs sweeps US and deepens crisis.