Juelz Santana Allegedly Had Oxycodone Pills During Airport Gun Bust

Juelz Santana's gun and drug possession charges just became more clear -- he allegedly had oxycodone on him during the airport bust ... TMZ has learned.

Law enforcement sources tell us Juelz had eight oxycodone pills in his travel bag when he was arrested for unlawful possession of a weapon and possession of a controlled dangerous substance at Newark International Airport last week.

He's due in court Wednesday to face the drug charge.

As we reported ... Juelz was arrested Monday after fleeing security when TSA found a gun in his carry-on bag in the x-ray tunnel.