SN instructed about Morphine. This is can slow or stop your breathing, especially when you start using this medicine or whenever you dose is changed. Never take morphine in larger amounts, or for longer than prescribed. Tell your doctor if the medicine seems to stop working as well in relieving your pain. Get emergency medical help if you have signs of an allergic reaction to morphine: hives; difficult breathing, swelling of your face, lips, tongue, or throat. Call your doctor at once if you have: slow heart rate, sighing, weak or shallow breathing, chest pain, fast or pounding heartbeats, extreme drowsiness, feeling like you might pass out. Morphine is more likely to cause breathing problems in older adults and people who are severely ill, malnourished, or otherwise debilitated. Common morphine side effects may include: drowsiness, dizziness; constipation, stomach pain, nausea, vomiting, headache, tired feeling, anxiety or mild itching.