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The Effects of Morphine on the Cardiovascular System

author image Naomi Parks
Naomi Parks has been a freelancing professional since 2004. She is a biochemist and professional medical writer with areas of interest in pulmonology, pharmaceuticals, communicable diseases, green living and animals. She received her Bachelor of Arts in biological anthropology from San Francisco University and her Master of Science in biochemistry from Pace University.
The Effects of Morphine on the Cardiovascular System
Morphine is an opiate often administered intravenously. Photo Credit: Kati Neudert/iStock/Getty Images

Morphine, an opiate, is useful in the treatment of cardiac ailments, according to the University of California School of Medicine. Nonetheless, there are various effects to the cardiovascular system resulting from morphine treatments. While some of these effects are benign and others effectively aid in treatment and anesthesia, there are known risks and complications to the cardiovascular system associated with morphine that can prove dangerous.

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According to the book "Clinical Anesthesia," typical doses of morphine have little effect on blood pressure or pulse. Alternately, higher doses of morphine can result in vasodilation, which is an expansion of blood vessels due to weakening smooth muscle surrounding them. This can result in a number of problems, including complications to the respiratory system, cardiovascular system and nervous system.

Cerebral Circulation

Respiratory depression and hypotension associated with morphine can affect cerebral circulation, according to the book "Clinical Anesthesia." This can result in cerebral vasodilation and increases in cerebral and spinal fluid pressure. Because of this characteristic, doctors administering morphine to patients with head trauma must exercise extreme care.


In addition to vasodilation, morphine can reduce baroreceptor reflexes; together, both effects can cause low blood pressure, or hypotension. Hypotension can trigger fainting spells as well as seizures.

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  • "The Cardiovascular Effects of Morphine: The Peripheral Capacitance and Resistance Vessels in Human Subjects"; Robert Zelis, Edward Mansour, Robert Capone and Dean Mason; The Journal of Clinical Investigation; December 1974
  • "Clinical Anesthesia"; Paul G. Barash, Bruce F. Cullen, Robert K. Stoelting and Michael Cahalan; 2009
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