Other central nervous system side effects of morphine are cough suppression, sedation, and dependence leading to addiction. This results in a delayed emptying of the stomach, constipa tion, and may also lead to urinary retention. Morphine can also cause histamine release, which causes itching of the skin and nose and a mild flushing of the skin. Morphine has little direct effect on the heart or blood pressure. How ever the blood pressure may fall slightly following the pain relief produced by morphine and also with the sedation which may be produced.
Significant hypotension following morphine is usually due to other causes such as hypovolaemia.
Occasionally patients with severe asthma may become wheezy. An unimportant, but early noticeable effect is that the pupils become small. This helps to differentiate respiratory depression caused by morphine from other causes. Precautions All patients who have been given morphine must be carefully observed for evidence of respiratory depression. This can be detected as a slow respiratory rate and a very sleepy patient with pin point pupils.