drug for an "off-label" route
There may be times when you can prescribe a drug for an "off-label" route...to minimize side effects...cut costs...or because the desired dosage form or strength is not commercially available.
For example, you can give pilocarpine eye drops orally for dry mouth. This is a lot cheaper and works as well as Salagen tablets.
Atropine eye drops and Atrovent nasal spray can be given sublingually for drooling...with fewer systemic effects than with oral anticholinergics.