Pain after acute burn injury is complex with much still not understood. After acute burn injury, both injured tissue and adjacent non-burned tissue, upregulate response to painful and non-painful stimulus (hyperalgesia and allodynia, respectively). The primary mechanism is believed to be nociceptive, but is interwoven with aspects of somatogenic, neuropathic, and psychogenic pathways. As such, opioid receptor agonists are an essential component for pain management after burn injury. Currently, high-dose fentanyl, oxycodone, hydromorphone, and morphine are used at profound doses to mitigate pain associated with daily care of patients with burn injuries. The majority of wound care and dressing changes are completed in non-intubated patients and rates of respiratory depression concerning.

High-quality data is controversial or lacking on the best approach for multimodal analgesia. Additionally, limitations exist for prescribing and monitoring some agents. While a multimodal approach may lead to a reduction in acute or chronic pain, adding a handful of medicines to eliminate a single agent leads to exponentially more side effects, risk of adverse effects, drug interactions, and pill burden. Drugs targeting neuropathic pain delay neural processing and are accompanied by cognitive slowing and responsiveness, which increases fall risk and limits rehabilitation participation. Gabapentin and pregabalin efficacies are highly debated with variable dosing recommendations. Side effects are common and include dizziness, somnolence, confusion, vision loss, respiratory dysfunction, peripheral edema, gastrointestinal discomfort or irregularities, or asthenia. If effective, serotonin-norepinephrine reuptake inhibitors response can be delayed by weeks and are known to cause significant weight loss, dizziness, asthenia, sleep disorders, and gastrointestinal dysfunction. Acetaminophen can help reduce background pain, but is hepatotoxic, depletes glutathione, and can mask fever. Nonsteroidal anti-inflammatory drugs carry significant safety concerns, including cardiovascular events, platelet dysfunction, bleeding, gastrointestinal toxicity, and renal failure. Local anesthetics have limited efficacy and dissipate quickly. Peripheral nerve blocks have mostly been studied for donor site pain, and placement requires specialized skills. Ketamine can be extremely helpful, especially in non-naïve patients with high-opioid tolerances but is approved as a moderate sedative and many state laws limit who can prescribe and/or monitor its administration. While ketamine does not depress respiratory drive, it is a hallucinogen, pro-deliriogenic, pro-arrhythmogenic, and carries its own concerns for gastrointestinal irregularities and drug dependence.

Opioid agonists bind to the mu opioid receptor (MOR), triggering downstream signaling through either G-protein-coupled or β-arrestin pathways. While the G-protein pathway is primarily involved in analgesia, β-arrestin has been shown responsible for adverse events, especially respiratory depression and gastrointestinal dysfunction. Additionally, the β-arrestin pathway terminates G-protein activation and induces endocytosis of the receptor, which can lead to reduced analgesia or opioid tolerance. Oliceridine is a biased, selective MOR agonist approved for treatment of acute pain. Oliceridine has shown a 3-fold preferential pathway activation of G-protein over β-arrestin. As a result, subsequent clinical trials have resulted in improved analgesia over placebo and morphine, while significantly reducing adverse events. To date there is no literature of use in patients with burn injuries. While it should be effective, efficacy and the potential for reduced adverse events need to be quantified. Current practice and guidelines, plead for better analgesia for patients with burn injuries.