A single shot of cortisol would not cause such a dramatic improvement in such a small amount of time.
In the final scene, the prescription is written for Vicodin ES, but the dosage on the prescription was 5-500, the amount found in regular Vicodin. Vicodin ES has 7.5mg of hydrocodone and 750mg of acetaminophen.
When the board - on which House's team has written several possibilities - is panned over, the word "diarrhea" is misspelled as "diarea", although it is spelled correctly on at least three other places.