Postoperative nausea and vomiting (PONV) are among the most common and distressing side effects that patients experience after anesthesia and surgery, affecting up to 30% of surgical patients and up to 80% of high-risk individuals. Although opioid analgesics are highly effective for managing postoperative pain, they are also major contributors to PONV. Understanding the risk of PONV associated with common opioid medications is essential for providing effective, patient-centered perioperative care.

The pathophysiology of opioid-induced PONV involves central and peripheral mechanisms. Centrally, opioids activate μ-opioid receptors in the chemoreceptor trigger zone (CTZ), which is located in the area postrema of the medulla. The CTZ lies outside the blood-brain barrier and responds readily to circulating emetogenic stimuli. When these receptors are stimulated, signals are sent to the vomiting center, triggering nausea and vomiting. Additionally, opioids delay gastric emptying and inhibit coordinated gastrointestinal motility by acting on μ-receptors in the gut wall. This contributes to gastric stasis and visceral afferent signaling, which enhances nausea (1).

Not all opioid medications carry the same PONV risk. Morphine, the archetypal opioid, is associated with a high incidence of PONV due to its hydrophilic nature and prolonged central and gastrointestinal activity. Fentanyl and sufentanil, which are more lipophilic and used primarily intraoperatively, have faster onset and shorter duration of action. This often results in a modestly lower PONV profile, though it is not negligible. Tramadol is often perceived as a lower-risk opioid due to its weak μ-agonist properties; however, it is paradoxically associated with considerable nausea. This is likely due to its dual mechanism of action involving inhibition of serotonin and norepinephrine reuptake, both of which are implicated in nausea pathways (2). Tapentadol, which also combines μ-agonism with norepinephrine reuptake inhibition, has demonstrated a reduced incidence of gastrointestinal side effects compared to oxycodone in some clinical trials, although evidence remains mixed (3).

Effective management of opioid-induced PONV begins with risk assessment. The most validated tool is the Apfel score, which includes four independent risk factors: female gender, non-smoking status, history of PONV or motion sickness, and postoperative opioid use. Patients with multiple risk factors should receive prophylactic antiemetic therapy, which is more effective than treatment alone. First-line pharmacological agents include 5-HT₃ antagonists (e.g., ondansetron), corticosteroids (e.g., dexamethasone), and dopamine antagonists (e.g., droperidol). Combination therapy, particularly in high-risk patients, provides superior protection compared to monotherapy.

Importantly, opioid-sparing and opioid-free strategies are increasingly emphasized in modern perioperative practice. Multimodal analgesia, which combines non-opioid medications such as acetaminophen, NSAIDs, gabapentinoids, and regional techniques (e.g., nerve blocks, epidurals), significantly reduces opioid consumption and thereby lowers the risk of PONV. Dexmedetomidine, an α2-adrenergic agonist with sedative and analgesic properties, has shown promising antiemetic effects and opioid-sparing benefits, especially in high-risk patients and ambulatory surgery settings (4).

Emerging treatments also aim to selectively counteract opioid-induced gastrointestinal effects without reversing analgesia. One such approach involves the use of low-dose, peripherally acting opioid antagonists like naltrexone or naloxone. Intranasal low-dose naltrexone has shown potential in preclinical models to reduce opioid side effects without compromising analgesic efficacy, although human data are limited (5).

Although opioids are essential in managing postoperative pain, they can trigger nausea and vomiting, necessitating a strategic and individualized approach. To optimize surgical recovery and patient satisfaction, it is essential to understand the mechanisms underlying opioid-induced PONV, choose agents with lower emetogenic profiles, and employ multimodal analgesia and evidence-based antiemetic prophylaxis.

References

1. Mallick-Searle T, Fillman M. The pathophysiology, incidence, impact, and treatment of opioid-induced nausea and vomiting. J Am Assoc Nurse Pract. 2017;29(11):704-710. doi:10.1002/2327-6924.12532
2. Edinoff AN, Kaplan LA, Khan S, et al. Full Opioid Agonists and Tramadol: Pharmacological and Clinical Considerations. Anesth Pain Med. 2021;11(4):e119156. Published 2021 Sep 6. doi:10.5812/aapm.119156
3. Comelon M, Raeder J, Drægni T, Lieng M, Lenz H. Tapentadol versus oxycodone analgesia and side effects after laparoscopic hysterectomy: A randomised controlled trial. Eur J Anaesthesiol. 2021;38(9):995-1002. doi:10.1097/EJA.0000000000001425
4. Bohringer C, Liu H. Is It Time for an Expanded Role of Dexmedetomidine in Contemporary Anesthesia Practice? – A Clinician’s Perspective. Transl Perioper Pain Med. 2018;5(3):55-62.
5. Micheli L, Di Cesare Mannelli L, Lucarini E, et al. Intranasal Low-Dose Naltrexone Against Opioid Side Effects: A Preclinical Study. Front Pharmacol. 2020;11:576624. Published 2020 Sep 18. doi:10.3389/fphar.2020.576624