My 14 yr old son who is takes 40 mg of Vyvanse & 20 mg of Lexapro a day, wants to take a GNC product for weightlifting and the the product if called muscle tech anabolic halo hardcore proseries (post workout) and contains some creatine, caffeine, phenylal

Be Careful. Since both vyvanse and Lexapro (escitalopram) have strong effects on the brain's neurotransmitters (norpramine, serotonin , etc) and different requirements for brain enzymes to deal with these drugs i would not take supplements that include creatine and others. Vitamins are generally safe and effective. Stay away from other nutritional products until your doctor can tell you whether they are safe to take.
It . It would be very dangerous and potentially harmful to take this product with his medications. I would strongly advise against it. The creatine, cafffeine, phenylalanin and his vyvanse and Lexapro (escitalopram) are not a safe combination and could affect his health.