Exactly what drugs cause morphine to come up on a drug test?

Narcs: A lot of prescribed opiods turn to morphine by the liver such as hydrocodone, oxycodone, codein. You may google for a complete list, but those are the most commonly prescribed.

Drug tests: False positives can occur if using cough suppressants, antihistamines, some antibiotics, codeine, asthma medications, sinus medications, nyquil, phenergan, (promethazine) poppy seeds, ultram.