Opioid Antagonists

There are several types of opioid antagonists you can give to reverse various effects of opioids. Some reverse most effects, including respiratory depression, while others counteract selected effects such as constipation or euphoria. You can also give opioid antagonists to reverse opioid overdose.

Opioid Antagonists

Opioid antagonists reverse the effects of opioids and treat opioid overdose. They also reverse the neonatal respiratory depression that can occur secondary to the mother receiving an opioid during labor.

Prototype and Other Medications

Naloxone – Medication Classification: Opioid Antagonists

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The prototype medication for opioid antagonists is naloxone. Other medications in this category include methylnaltrexone, nalmefene, naloxegol, and naldemedine which relieve opioid-related constipation; and naltrexone, which prevents the euphoric effects of opioids for clients addicted to opioid agonists. You can give it to treat opioid use disorder in much the same way you give disulfiram for alcohol use disorder. Alvimopan is an opioid antagonist used to accelerate the recovery time of clients who have upper and lower GI surgeries with a bowel resection and anastomosis (reconnecting the intestine). 

Expected Pharmacologic Action

Opioid antagonists are an antagonist in the purest sense of the word. They produce their effects by blocking opioid receptors, effectively reversing, or antagonizing the effects of opioids.

Adverse Drug Reactions

The most significant adverse drug reaction of opioid antagonists is ventricular arrythmias. You can expect that heart rate and respiratory rate will increase but remain alert for abnormal rates or rhythms. Abstinence syndrome, also called withdrawal syndrome, may precipitate in clients who are opioid dependent. Manifestations that occur in opioid-dependent clients include hypertension, vomiting, and tremors.

Safety Alert

Naloxone is a valuable medication used to reverse respiratory depression that accompanies overdose of an opioid analgesic. If a client who is opioid dependent receives the medication, abstinence syndrome may occur. If you are caring for a client who overdoses on a CNS depressant medication outside the hospital setting, you may not know if the client is physically dependent on opioids. Have equipment available in case the client does go into full-blown withdrawal, including suction equipment to prevent aspiration secondary to vomiting. Administer naloxone in several small doses to a client who overdoses, with a space of time in between injections to minimize withdrawal manifestations.

Interventions

When giving an opioid antagonist, closely monitor for dangerous elevations in clients’ blood pressure, in addition to other vital signs such as respiratory rate, heart rate, heart rhythm, oxygen saturation, and level of consciousness for manifestations of opioid withdrawal for clients who are opioid dependent. Naloxone has no effect on medications that are not opioids. Use it with caution in clients who have cardiac irritability, a head injury with increased intracranial pressure, brain tumor, or seizure disorder.

Administration

You can administer naloxone intramuscularly, intravenously, subcutaneously, sublingually, and intranasally. When you give the medication intravenously, titrate the dose very carefully. Monitor vital signs every 5 to 15 min throughout its administration and for several hours after its conclusion. The effects of naloxone last 60 to 90 minutes, so respiratory depression can recur while there’s still an excessive amount of the opioid in the client’s bloodstream. Be aware that after administering naloxone the client’s pain may return as the medication blocks analgesic effects of the opioid. Naloxone can also cause an acute withdrawal in clients who are opioid dependent. Prepare to administer naloxone every 2 to 3 min until reversal of undesirable effects occurs. Prepare to repeat the dose as the opioid effects can extend beyond the effects of the reversal agent. Finally, observe for nausea, vomiting, tachycardia, and diaphoresis, which accompanies opioid reversal, as well as withdrawal in clients who are dependent on opioid medications.

Client Instructions

When preparing to administer an opioid antagonist to a client who is awake, inform them of the need for the medication. Be sure to warn clients of the possible adverse drug reactions and return of pain.

Contraindications and Precautions

Clients who are opioid dependent or have respiratory depression due to nonopioid medications should not take naloxone. Naloxone has no effect on medications that are not opioids. Use it with caution in clients who have cardiac irritability, a head injury with increased intracranial pressure, brain tumor, or seizure disorder.

Interactions

As you might expect, opioid antagonists decrease the effects of opioids.