There's a caveat with inactive ingredients, but it goes both ways
The only caveat to the totally equivalent concept is that inactive ingredient list. This isn't the chemical that's supposed to make you feel better, but what else needs to be added to the medication to hold it together.
In a capsule, for example, the powder inside might contain the drug itself, while the gel containing the powder could be made of inactive ingredients. "Sometimes the inactive ingredient will affect the delivery of the molecule in terms of how quickly the body will metabolize it," Dr. Altman explains. "Patients could feel an effect quicker or slower."
But, he points out, this difference can go either way -- "Patients may idiosyncratically respond better to one form of a medication than another." In fact, he has patients who will ask him for a specific version, but it's not always the most expensive one. Switching prescription medications should obviously be discussed with the doctor, but for most conditions, it doesn't end up making a difference.