Certified Hospice and Palliative Assistant (CHPNA) Practice Test

What is a dose-limiting side effect of morphine?

1. Constipation

2. Respiratory depression

3. Myoclonus

4. Nausea and vomiting

The correct answer is: Myoclonus

The most appropriate choice for a dose-limiting side effect of morphine is respiratory depression. This phenomenon occurs when the drug depresses the central nervous system to the point where it can significantly lower the respiratory rate, leading to insufficient oxygen absorption and high carbon dioxide levels in the blood. Because respiratory depression can be life-threatening, it is often the key factor that dictates the maximum dose that can be safely administered to a patient. While constipation, myoclonus, and nausea and vomiting are all common side effects of morphine use, they are generally manageable and can often be addressed with additional medications or supportive care. Constipation is particularly common in opioid use, but it tends to be more chronic and can usually be treated with laxatives. Myoclonus, which refers to muscle spasms or twitching, can occur but is not typically life-threatening and does not impede the use of morphine as severely as respiratory depression does. Nausea and vomiting can also be treated with antiemetics, making them less of a concern when determining safe dosage limits. Therefore, respiratory depression stands out as the most critical and significant dose-limiting reaction associated with morphine.