Rx (prescription)

How to read it

The American Heritage Dictionary defines Rx as a prescription for medicine, and more loosely a remedy or solution for a problem; it traces the spelling to ℞, the symbol used in prescriptions, an abbreviation of Latin recipe, the command form of recipere, “to take”. Unicode encodes the sign as U+211E, named PRESCRIPTION TAKE and glossed “recipe”. In 18th-century prescriptions it was read the same way: the historian Robert Woods glosses it as “recipe, take thou”. It opens the first part of a prescription, the superscription, which is followed by the drugs and quantities, the directions for making them up, and the directions for the patient (Sig). MedlinePlus lists Rx as prescription, and on the same list DX is diagnosis (Dx).

Also searched as: ℞, rx meaning, rx medical abbreviation, rx symbol, what does rx mean.

Did ℞ come from the sign of Jupiter?

No reliable source we found supports it. The dictionaries and Unicode derive ℞ from recipe, and the History.com writer Elizabeth Nix says most sources do. The Jupiter story is old. The physician Howard Haggard wrote in Devils, Drugs, and Doctors (1929) that the sign is not an abbreviation of recipe but “an invocation to Jupiter, a prayer for his aid to make the treatment effective”; the example he printed is a title page on which every R is crossed. A revised edition of Brewer’s Dictionary of Phrase & Fable splits the difference, reading the letter as recipe and its flourish as the symbol of Jupiter, and records a third claim, that it stood for Responsum Raphaelis because 17th-century physicians held that the angel Raphael taught the virtues of drugs.

The Eye of Horus theory

A second popular story, that ℞ grew out of the Eye of Horus, is one Nix reports among several alternative theories, against the recipe derivation she says most sources give. She also notes that the mortar and pestle appears on drugstore signs alongside Rx.