Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Answering your question, Sheikh Kifah Mustapha, the Imam and Director of The Prayer Center of Orland Park and representative for Dar El Fatwa of Lebanon in the US, states:
According to Wikipedia, morphine is a narcotic drug used to relieve pain from materials found in opium poppy plant. It is not a form of food nor is it a food supplement.
For that, if the medication is in the form of an injection in the vein, it does not break your fast. But if it was a pill which will be swallowed with a pill cover, then yes it will break your fast.
Remember, though, if you are in pain of illness and you need to eat or take other medications to stay healthy you should consider breaking your fast.
Allah Almighty knows best.