When mixing Solu-Medrol 40 mg with 1 ampoule of morphine 10 mg no problems occur. However, 20 mg of morphine is added then the whole is cloudy...

Solu-Medrol contains methylprednisolone after succinate and the solution has a pH between 6.5 and 8 for optimal stability and solubility. Morphine solution usually has a slightly acidic pH for the same reasons. If they are mixed then we obtain a pH, which is not suitable for both products. I suspect that part morphine is down.