John Clark Gable -- Charged with DUI & Hit-and-Run After 6-Car Collision

John Clark Gable -- the son of Hollywood legend Clark Gable -- just got slapped with a hit-and-run charge in addition to DUI following his crazy arrest back in April ... when he crashed into 6 parked cars.

The two charges -- both misdemeanors -- were just filed in L.A. If convicted he faces jail time, but that's very unlikely.

Law enforcement sources tell TMZ, Gable was NOT drunk at the time of his arrest ... officials believe he was under the influence of prescription medication.

TMZ broke the story ... Gable was busted in Malibu after allegedly smashing into 6 parked cars on Pacific Coast Highway. Gable told us he had lost consciousness behind the wheel and woke up just after the accident had occurred.

As for the Rx meds, Gable said he was taking pills for a minor leg injury he suffered while mountain biking, but believes a brain aneurysm might have been responsible for the crash.