A Review of Systemic Opioids Commonly Used for Labor Pain Relief

Abstract

Parenteral opioids for pain relief during labor have been the subject of research for many decades. Commonly used systemic opioids provide limited pain relief during labor yet are used extensively for managing labor pain. These opioids share similar pharmacologic profiles but differ in potency, pharmacokinetics, and side effects. This article reviews the pharmacokinetics, pharmacodynamics, and clinical research related to the commonly used systemic labor pain analgesics morphine, meperidine, fentanyl, remifentanil, butorphanol, and nalbuphine.

Effects of μ-Opioid Receptor Agonists in Assays of Acute Pain-Stimulated and Pain-Depressed Behavior in Male Rats: Role of μ-Agonist Efficacy and Noxious Stimulus Intensity

“…Consistent with previous findings, morphine produced a dose-dependent blockade of acid-induced depression of ICSS (Pereira Do Negus et al, 2010b). This study extends these previous findings by showing that acid-induced depression of ICSS was also blocked by other m-agonists that are used clinically in humans as analgesics (Sunshine et al, 1997;Gutstein and Akil, 2006;Anderson, 2011;Calderon and Copenhaver, 2013;Chen et al, 2014). These findings are also consistent with the ability of m-agonists to block pain-related depression of other behaviors produced by other types of noxious stimuli .…”

Polymorphisms associated with fentanyl pharmacokinetics, pharmacodynamics and adverse effects

“…However, almost 40% of the volunteers experienced somnolence, which was significantly associated with the carriage of the OPRM1 A118G G allele. The OPRM1 gene encodes for the μ‐opioid receptor, thus having a direct implication on the analgesic effect that fentanyl produces. Specifically, the A118G substitution is considered to underlie discrepancies in the analgesic requirements and sensitivity to opioids as it has been related with a reduced signal transduction, reduced expression of OPRM1 and reduced binding affinity for opioids such as morphine .…”

“…Fentanyl evokes its sedative effect mainly through activation of μ‐opioid receptors, which are abundant in the central nervous system and the peripheral nervous system. Due to its high lipophilicity, fentanyl is able to easily cross the blood‐brain barrier (BBB), thus having great potency (between 75 and 200 times more potent than morphine) . Considered as one of the most frequent analgesics, it produces adverse effects such as vomiting, nausea, gastrointestinal constipation, respiratory depression, dependence and tolerance .…”

“…Due to its high lipophilicity, fentanyl is able to easily cross the blood‐brain barrier (BBB), thus having great potency (between 75 and 200 times more potent than morphine) . Considered as one of the most frequent analgesics, it produces adverse effects such as vomiting, nausea, gastrointestinal constipation, respiratory depression, dependence and tolerance . However, it produces less adverse effects (AEs) than morphine as lower doses are required to obtain similar analgesic effects …”

“…2 Fentanyl evokes its sedative effect mainly through activation of μ-opioid receptors, which are abundant in the central nervous system and the peripheral nervous system. Due to its high lipophilicity, fentanyl is able to easily cross the blood-brain barrier (BBB), 3,4 thus having great potency (between 75 and 200 times more The authors are grateful to the volunteers and the effort of the staff of the Clinical Trial Unit of Hospital Universitario de la Princesa. potent than morphine).…”