Description: Opiate antagonists are drugs that bind to opioid receptors more tightly than opioids but do not cause the effect of opioids. In other words, opiate antagonists block the effects of drugs such as morphine and heroin. Opiate antagonists are often used to reverse the effects of opioid overdose. In this circumstance, opiate antagonists are used for a very short period, simply to save a person’s life. In other instances, opiate antagonists are used at lower doses as chronic treatment for opiate addiction. Opiate addiction is treated with drugs such as buprenorphine, which are partial agonists of opioid receptors. These drugs partially stimulate and partially block the effect of opiates at the opioid receptor.
When opiate antagonists are given to treat opiate overdoses, opiate antagonists side effects are not the primary concern. Nevertheless, opiate antagonists such as naloxone can put a person into immediate opioid withdrawal, causing a tremendous output from the sympathetic nervous system. This can result in high blood pressure, racing heart, life-threatening heart arrhythmias, and cardiac arrest. At the very least, acute doses of naloxone may cause restlessness, diarrhea, nausea, vomiting, severe abdominal cramping, muscle aches and pains, and sweating. Often these opiate antagonists side effects are short-lived, but in the case of life-threatening arrhythmias, they can be fatal.
Journal of Addiction Medicine “American Society of Addiction Medicine [ASAM] National Practice Guideline for the Use of Medications in the Treatment of Addiction Involving Opioid Use,” Sept 2015).
Common Opiate Antagonists Side Effects
Opiate antagonists side effects are more of a concern for people who take chronic doses of opiate antagonists. For example, people may take oral naltrexone each day for alcohol dependence or opioid dependence. In these cases, chronic opiate antagonists side effects emerge.
The most common opiate antagonists side effects (occurring in >10% of patients), with buprenorphine as an example, include:
- Abdominal cramping
- Abdominal pain
- Decreased appetite
- Decreased energy
- Elevated liver enzymes
- Elevated muscle enzymes in the blood
- Joint aches
- Muscle aches
- Syncope (passing out)
(Suboxone (buprenorphine) drug label, as reported by the U.S. Food and Drug Administration).
Understand Your Risks for Side Effects with the Rxight® Genetic Test
Buprenorphine is one of the most commonly used medications for opioid withdrawal and opioid dependence treatment. Buprenorphine is a substrate of the cytochrome P450 enzyme 3A4 (CYP3A4), which means it is metabolized through the CYP3A4 enzyme. Most people have normal CYP3A4 enzyme function, which means buprenorphine will be metabolized rather predictably. However, people who are rapid or poor CYP3A4 metabolizers will have unexpectedly low or high buprenorphine levels in the body. In both cases, this may lead to opiate antagonists side effects. (Drug Metabolism and Disposition “Interaction of buprenorphine and its metabolite norbuprenorphine with cytochromes p450 in vitro,” Jun 2003).Pharmacogenetic testing is a new method that assesses a person’s unique genetic makeup. It can provide patients with a description of their liver enzyme function, including CYP3A4. MD Labs is proud to offer Rxight® pharmacogenetic testing for opiate antagonists. The panel includes over 200 medications across over 50 drug classes. The panel includes a full assortment of genotypes for cytochrome P450 enzyme including CYP3A4, CYP2D6, and many others. Taking the Rxight® genetic test will help the patient and prescriber understand if they are rapid CYP3A4 metabolizers and if they are able handle medications such as optiate agnosists appropriately at standard doses.
Contributors to this Article:
Michael Sapko, MD, PhD; Deborah Kallick, PhD, Medicinal Chemistry