Well since you're open to medications...
Any cholinergic - choline
for example (a common dietary supplement) can produce pupil constriction (miosis). Conversely any anti-cholinergic will do the opposite and produce mydriasis (dilation), Atropine
for example as SWIJasim mentioned. Opioids
also all produce miosis.
In terms of other prescription medications, mirtazapine
both produce a degree of miosis. SWIM
has personally experienced this on Mirtazapine, it makes his eyes quite beady and evil looking the pupils get so small sometimes.
Anti-psychotics like olanzapine, haloperidol and quetiapine all produce mioses as well.
As for pupil dilation, anti-cholinergics, serotonergics (SSRIs, SNRIs, 5-HTP, Tryptophan included), and stimulants
will all produce that.
Now just because SWIM listed all those things doesn't mean they should be tried, as producing an exact pupiliary diameter on a regular basis through means of medication and supplementation in order to hide ongoing drug
abuse really is rather impossible and a somewhat silly waste of effort!