Naloxone

Lore & Background

It is a non-selective and competitive opioid receptor antagonist that reverses depression of the central nervous system and respiratory system caused by opioids. Administration to opioid-dependent individuals may cause symptoms of opioid withdrawal, including restlessness, agitation, nausea, vomiting, fast heart rate, and sweating. To prevent this, small doses every few minutes can be given until the desired effect is reached. In those with previous heart disease or taking medications that negatively affect the heart, further heart problems have occurred.

Reader's Guide

Naloxone is included as a part of emergency overdose response kits distributed to heroin, fentanyl, and other opioid drug users, and to emergency responders, which has been shown to reduce rates of deaths due to overdose. It is also used as an antidote in clonidine overdose, though controversy exists regarding its efficacy. Naloxone is poorly absorbed orally or sublingually, so it is often added to oral or sublingual opioid preparations to prevent non-medical use. However, if such a combination is injected by a regular user of buprenorphine, the naloxone may fail to produce an antagonist effect. Naloxone has also been studied for improving blood flow in shock and for opioid-induced constipation, but evidence is inconclusive. It is on the World Health Organization's List of Essential Medicines and is available over-the-counter.

Did You Know?

• Naloxone blocks the effects of opioids for 30 to 90 minutes.
• It can be used as an antidote in clonidine overdose, though efficacy is controversial.
• Naloxone is poorly absorbed when taken orally or sublingually, so it is added to some opioid preparations to deter injection.
• Small amounts of naloxone are excreted in breast milk, but it is unlikely to affect a breastfeeding infant due to poor oral absorption.