This article is from the Magick Tantra FAQ, by Tyagi Nagasiva firstname.lastname@example.org, Catherine Yronwode email@example.com with numerous contributions by others.
Apparently not, but overemphasis on avoidance of orgasm may
lead to a special form of "performance anxiety" or to some
temporary physical discomfort, especially in men.
In the practice of sex magic(k), orgasm is often the focal
point of the ceremony or spell, and its resultant products
(e.g. mingled sexual fluids) may be ritually consumed,
offered to a deity, or used to create a sigil or talisman.
Such mingling requires that both parties be free of
sexually transmitted diseases, for these can be more
harmful in the long run than refusal to have an orgasm!