Silicon Blood
https://www.amazon.com/dp/B06XQKJY2G/
In the near future, the drug cartels of South America establish their own criminal nation, Cordillera, and proceed to flood the world with cocaine and political corruption.
America responds by using the new science of nanotechnology to produce microscopic machines – “nanobots” – to eradicate such drugs once and for all. But these tiny devices can also be used to create new kinds of drugs inside a human body – a “pharm” -- or to devour it from within.
After a catastrophic nano-plague, a new and powerful drug lord, El Hombre – “The Guy” – uses nanobots to set up a worldwide drug ring, harvesting new drugs from human bodies and enforcing obedience with threats of devourment.
Jerry Gade, a nano-engineer with a horrific secret, fights back.
The struggle between Gade and The Guy takes place in both the human domain and in the invisible world of their own nano-creations.
The outcome of their battle will determine the future of the human race.