Many people argue that medical marijuana can patients suffering from chronic pain and other medical conditions. on the other hand, this drug has been used to ease the pain of chemotherapy treatments.

which of the following transitions is a better choice than "on the other hand"?

Moreover, Besides, Also, Furthermore.

Explanation:

All of these words above express addition, you can add more information after them,  the one you used is more suitable to show contrast between two different things. The two uses that you mentioned are both good, so on the other hand is not the correct option here, if you use on the other hand what comes next should be a negative effect of the use of medical marijuana.

the light at the intersection of gurley and montezuma will turn green exactly three seconds after the light at the intersection of gurley and marina.