L-carnitine or L-arginine both help to fix nitric oxide which helps with vasodilation, which increases blood flow, similar to what Viagra does, but not as strong an effect, so daily supplementation is required. Viagra was developed to increase the blood flow in patients with pulmonary hypertension, PHT where the pulmonary artery loses elasticity and becomes less flexible, causing stress on the heart and eventual heart failure. The side effect of Viagra got it marketed as a sexual dysfunction aid, but it is also used for its original purpose, treating PHT, which is common in thal intermedia and often found in majors, as well, and does seen to have some effects on thal minors as they age. Long term supplements to help keep the blood vessels flexible is something I recommend.
Vitamin B-6 can also help with sexual function, although some people are bothered by the harmless flushing that B-6 can cause.