I have arthritis that requires that I take several medications. The arthritis makes me very tired and the medicine also makes me sleepy. Would it be alright to pray my Maghrib and Isha together. Its really difficult to stay up until Isha and several times I didn't wake up. Sometimes its hard to just stay awake for Maghrib.

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Basically, you are ordered to perform every prayer on its prescribed time and the time of Isha extends till the rising of Fajr (dawn) in early morning. So, Isha prayer can be performed anytime before dawn. You may also try to perform Isha prayer right after its fixed time starts. But, if there is much hardship for you in doing so and you fear that you might not wake up before Fajr then the rule of a sick person as far as performing prayers applies to you, so you may perform Isha prayer with Maghrib prayer combining both of them during the time of Maghrib prayer.
Allah knows best.