Severe pain after root canal. how long can it last if i'm on medication?

Often 1 or 2 weeks: Pain to pressure on the tooth is common after root canal and can last up to two weeks. Severe pain is often caused by the tooth being in hyperocclusion (hitting the opposing tooth too strongly). The dentist can slightly shorten the tooth and relief will come in a day or two. If severe pain persists, a persistent infection or fractured root may be the cause. See the dentist who did the rct.

2 days: The root canal pain should be gone within the first 2 days, if not immediately. Consider consulting an endodontist for an evaluation if your root canal continues to be painful after 2 days.