It is impossible to RATE a similar drug against another for the same disorder because...... When a drug is used on a group of 1000 patients, statistics are gathered to examine what the drug does as to efficacy, safety, side effects (none fatal),  drug interactions and a slew of other possible problems. If you test this same drug on another group of 1000 patients you may get a similar picture of efficacy, however, one particular side effect of obesity or drowsiness is virtually non-existent in the second drug. Many patients have discontinued their drug because of obesity or drowsiness. This new one offers the possibility of giving the patient the opportunity to try another drug that works as well but does not have a particular side effect so that the patient stays on the drug. The second drug is essentially the same as the first, however, a single side effect mat be the difference between the two drugs in SOME, NOT ALL, PATIENTS. A drug recently approved for bi-polar disease and schizophrenia (TO BE MARKETED IN THE 4Q) is in the same class of compounds as prior drugs and is a little more effective, however, the side effect of obesity is  SO MARKED IN THE EARLIER VERSIONS THAT THIS IS ENOUGH REASON TO SWITCH THE PATIENT FROM ONE TO THE NEEWER VERSION. Also, the incidence of obesity with the increased risks of serious stroke, heart disease, etc. warrants changing all patients to the newer version.

The cost of developing a drug that may turn out to be very little better or not as good as the first drug, however, no company will ever invest in a second drug if their market was limited to only the "left overs" of the first drug. There are many "statin" drugs. Most are no better than the first, however, in my case, the first one caused me so much pain in my thigh muscles that I had to discontinue it. I was lucky that there was a second "statin" available that had no effect on my thigh muscles. It happens that my sister and wife had the same problems and shifted to the sec ond with no side effects.