Ask HN: Why do some medicines come as pills and others as capsules?

  - they protect the medicine better from light and moisture and oxygen than tablets
  - powder in capsules dissolves faster, more evenly and thus the dose can be frontloaded instead of spread out
  - beads in capsules can be coated to control dosage rates or deliver one medication before another. I.e. if the active drug irritates the stomach a coating can counteract that or keep it from dissolving until it reaches the intestines. Extended release medications usually use these coatings to slow down absorption
  - capsules can carry multiple physically separated chemicals that are too reactive to be allowed to touch
  - the binders in the pill interfere with the medication
  - capsules can mask the taste better

First and foremost is the way to deliver the _active substance_. Can be immediate (pills are not the best for immediate delivery), delayed (most common) or extended release (e.g. the AS gets released in doses over a period of time).

Capsules IIRC can only deliver immediately but AS on capsules has faster absorption compared to pills.

Cost is another factor: AFAIK pills are usually cheaper - although I don't work at the industry so don't quote on me on this.

So it's the way you want to be delivered, characteristics of the AS, cost, etc.

source: I have a 5-year degree (EU) in Pharmaceutical Sciences.