Propranolol is not a narcotic, mind-altering drug. And urine drug screens don't test for it.
Urine drug tests are designed to be specific for narcotic drugs. And drugs like propranolol cannot cause false positive results.
But if you eat some bakery products with poppy seeds. Then your urine drug screen can become positive for Opium, Heroin, Morphine, and Codeine. And if you take some cold medicines. Then your urine drug screen can become positive for Methadone.