Specific to the physical make-up

[Rambam] “He writes that a medical treatment must be specific to the physical make-up of the patient at that particular time. (Moreh Nevuchim, Chailek Gimmel, perek 34). In other words, not only do different patients require different prescriptions for the same ailment, but even the same patient may require different treatment when any of the factors impinging upon his constitution have changed.” 

Rabbi Moshe Meiselman, Torah and Science, 2013, Israel Bookshop, Lakewood, p. 227.