When this spell is placed upon a poisoned individual, it greatly slows the effects of venom, if cast upon the victim before the poison takes full effect. (This period, known as the onset time, is known to the DM.) While this spell does not neutralize the venom, it does prevent it from substantially harming the individual for the duration of its magic in the hope that, during that spell period, the poison can be fully cured.
The material components of the slow poison spell are the priest's holy symbol and a bud of garlic that must be crushed and smeared on the wound (or eaten if poison was ingested).
Notes: Common for clerics and druids (PHB).