DLPA L-Phenylalanine, DL-Phenylalanine, and L-Tyrosine: Should be used with physician guidance if you have elevated blood pressure, heart problems, or skin cancer. Should be avoided in persons with phenylketonuria or pregnant or nursing women. Some research suggests that people with tardive dyskinesia may process phenylalanine abnormally. Until more is known, it makes sense for people with this condition to avoid phenylalanine supplementation.