There are “oracle pills” sometimes called “smart pills,” but I suspect this is not what you’re after. The following is from my draft book, Monumental Lies: Early Nevada Folklore of the Wild West (currently awaiting approval for publication by my press’s Editorial Advisory Board – having received two positive peer reviews):

Beginning in the 1960s and occasionally over the course of subsequent decades, some old hand would invite me to try smart pills. I never accepted and perhaps consequently remain a shade short of smart and some might assert the shortcoming is more than slight. A smart pill is a folk remedy for stupidity. How and when smart pills entered Nevada folklore is not easy to determine, but the motif appears to have roots that reach back to the Italian Renaissance, so it may have been in Nevada long before I first heard of the cure.

In 1977, the folklorist Richard Bauman recorded a story about a smart pill in Oklahoma. In the narrative, someone took to selling dupes rolled up pieces of dog dung, telling his victims that if swallowed, the pill would make them smarter. As the story unfolds, a fool purchased and swallowed several pills, repeatedly indicating that he did not feel any smarter. The cycle repeats until he finally realizes what the pills are, at which point he objects, but the trickster declares that since the man has realized the ploy, he has, indeed, become smarter, so the pills have worked.

My invitations to become smarter have occurred in the wide-open Nevada terrain, with joking offers of rabbit or deer pellets. The point here is the role of deception as part of western folklore. Besides being an essential element of the hoax, deceit is also at the heart of tall tales, burlesque lies, and practical jokes, all of which have important places in regional traditions. The smart pill ranks among these, but as Bauman demonstrates, the tradition does not merely consist of the execution of such a deception. The incident can take on its own life when it is subsequently described as a traditional story.

The citation for the first paragraph provides a reference to the Motif Index, the source that folklorists often use to track down the answers to questions like yours:

An analogue of the smart pill is the oracle pill: Stith Thompson, Motif-Index of Folk Literature (Bloomington: Indiana University Press, 1955-1958): “Motif K114.3.1: Virtue of oracular pill proved. The dupe takes it. ‘It is dog’s dung.’ He says, spitting it out. The trickster says that he is telling the truth and demands pay”; Thompson cites D. P. Rotunda, Motif-Index of the Italian Novella (Bloomington, Indiana, 1942) and Albert Wesselski, Die Begebenheiten der beiden Gonnella (Weimar, Germany, 1920) Numbers 4, 4a, 106 and 9, a discussion of an Italian buffoon dating to the fifteenth century; Gene Hattori was the most recent person to suggest that I would benefit from ingesting smart pills (ca. 1995). He should be ashamed.

References more in line with what you’re asking about include the following from India: D1347.3.1 Magic pills insure birth of twin sons (Cf. D1243); D765.1.1 Disenchantment by removal of enchanting pill from mouth; D551.6.1 Transformation by placing pill in mouth (cf. D1243); and J621.1.1 Snake gives away magic pills later used to kill him.

Thompsons coverage of east Asia is not great, but he does mention China in this context: D444.3 Transformation: pill to white rabbit.

The comparison to D 1243 is to a heading called “Magic pill.” It includes references to material from China and India but also to Arabic folklore.

The motif index is not perfect: its method of cataloguing can be questions, and given the vast scope of international oral traditions, it is hardly complete. But with six massive volumes, it is impressive, and it serves as a place to start. Thompson was at his strongest in Europe (especially with the folktale, where one would expect magic pills) – and then in India. It is notable that his index does not mention Europe when it comes to magic pills. I wouldn’t take this absence as being too significant, but it is noteworthy.