Is it okay to split drug pills in half?

Generally yes: Any solid pill can be split in half and some actually have a score built in for this purpose. This can be a way to lower the cost as the larger pill frequently costs less than two smaller pills. Capsules cannot be split, as the contents spill out uncontrollably although capsules can be opened and the contents put in a slurry for ingestion if the capsule cannot be swallowed.