New Drug Blocks Morphine's Effects on Breathing—But Not on Pain

Repinotan Could Become Part of Standard Care for Postoperative Pain

Newswise — A new drug called repinotan blocks the respiratory depressant effects of morphine-like opioid drugs—without altering their potent pain-relieving effects, according to a study in the October issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

If the promising results of animal studies are borne out by future research, then repinotan could become an important part of safe, effective pain control after surgery. The new study was led by Dr. Ulf Guenther of University of Ulm, Germany.

Subcutaneous Oxygen Levels during Surgery Predicts Later Infection RiskThe researchers performed a series of experiments to see how repinotan influenced the effects of morphine. Although morphine and related drugs (opioids) are highly effective in treating pain after surgery, they share a common characteristic: they decrease the drive to breathe. This is a potentially serious side effect that can limit the use of opioid drugs for pain control.

In the study, rats were given a morphine dose high enough to slow the breathing rate. When the animals were subsequently treated with repinotan, their respiratory rate rapidly returned toward normal.

At the same time, repinotan did not alter the pain-blocking effects of morphine. This is especially important because, although other drugs are available to reverse the respiratory depressant effects of opioids, they also reverse the pain-relieving effects.

There were no serious cardiovascular side effects with repinotan, although it did cause a drop in blood pressure.

"For years, investigators have tried to develop an opioid that produced the profound analgesia of morphine, but without the effects on breathing rate," explains Dr. Steven L. Shafer of Columbia University, Editor-in-Chief of Anesthesia & Analgesia. More recently, specific types of drugs have been developed that selectively reverse morphine-induced depression of breathing. Repinotan is the first drug of this type that has proven suitable for studies in humans.

"This is an incredibly exciting development in opioid pharmacology," Dr. Shafer adds. "A drug that blocks the ability of opioids to suppress breathing, while not interfering with the pain relief, would be a huge advance in pain management and patient safety. Unless the drug had other toxicities, such a drug would immediately become the standard of care for post-operative patients receiving opioids."

Read the full study in Anesthesia & Analgesia About the IARSThe International Anesthesia Research Society is a nonpolitical, not-for-profit medical society founded in 1922 to advance and support scientific research and education related to anesthesia, and to improve patient care through basic research. The IARS contributes nearly $1 million annually to fund anesthesia research; sponsors an annual forum for anesthesiology leaders to share information and ideas; maintains a worldwide membership of more 15,000 physicians, physician residents, and others with doctoral degrees, as well as health professionals in anesthesia-related practice; sponsors the SAFEKIDS initiative; and publishes the journal Anesthesia & Analgesia. Additional information about the society and the journal may be found at www.iars.org and www.anesthesia-analgesia.org.

About Anesthesia & AnalgesiaAnesthesia & Analgesia was founded in 1922 and was issued bi-monthly until 1980, when it became a monthly publication. A&A is the leading journal for anesthesia clinicians and researchers and includes more than 500 articles annually in all areas related to anesthesia and analgesia, such as cardiovascular anesthesiology, patient safety, anesthetic pharmacology, and pain management. The journal is published on behalf of the IARS by Lippincott Williams & Wilkins (LWW), a division of Wolters Kluwer Health.