Opioid Agonist–Antagonist Drugs

Opioid agonist–antagonist drugs are a class of medications that interact with opioid receptors in the body. They produce limited responses (partial agonists) or no effect (competitive antagonists) at these receptors. These drugs also often have partial agonist actions at other types of opioid receptors, such as kappa (κ) and delta (δ) receptors. This article will explore various opioid agonist-antagonist drugs, their pharmacokinetics, clinical uses, side effects, and more.

Common Opioid Agonist–Antagonist Drugs

Here are some common opioid agonist-antagonist drugs:

Drug NameActionReceptor BindingClinical UsesDose per kgOnset of ActionDuration of Action
PentazocinePartial agonist/antagonistμ, δ, κ receptorsModerate pain relief0.5-1 mg/kg15-30 minutes3-4 hours
ButorphanolPartial agonist/antagonistμ, κ receptorsPostoperative pain, migraines0.01-0.02 mg/kg5-10 minutes3-4 hours
NalbuphinePartial agonist/antagonistμ, δ receptorsAnalgesia, cardiac catheterization0.1-0.2 mg/kg2-3 minutes3-6 hours
BuprenorphinePartial agonist/antagonistμ receptorsModerate to severe pain0.001-0.006 mg/kg15-30 minutes8-12 hours

Here’s an overview of the pharmacokinetic properties of these drugs:

Drug NameAbsorptionMetabolismElimination Half-LifeExcretion
PentazocineWell absorbed after oral or parenteral administrationExtensive hepatic metabolism2 to 3 hoursUrine (5-25% unchanged)
ButorphanolRapid and complete absorption after IM injectionMetabolized in the liver2.5 to 3.5 hoursBile and urine
NalbuphineRapid onset of action and duration similar to morphineLiver metabolism3 to 6 hoursUrine
BuprenorphineRapid onset and prolonged duration of actionExtensive liver metabolism8 hours or moreBile and urine
Clinical Uses

These drugs have various clinical applications:

  • Pentazocine: Used for moderate pain relief, especially when there’s a high risk of physical dependence. Can be administered epidurally for rapid but shorter-lasting analgesia.
  • Butorphanol: Effective for postoperative pain and migraine pain. Limited intraoperative use.
  • Nalbuphine: Useful for analgesia during cardiac catheterization. Can reverse opioid-induced respiratory depression while maintaining analgesia.
  • Buprenorphine: Effective for moderate to severe pain, including postoperative, cancer-related, renal colic, and myocardial infarction pain.
Side Effects

Common side effects and other considerations for these drugs:

Drug NameCommon Side EffectsOther Considerations
PentazocineSedation, diaphoresis, dizziness, nausea, vomiting, dysphoriaIncreases plasma catecholamine levels, crosses placenta
ButorphanolSedation, nausea, diaphoresis, minimal dysphoria, increased blood pressureLimited intraoperative use, reversal of opioid-induced respiratory depression
NalbuphineSedation, dysphoria (increases with dose), no significant effects on blood pressureUseful for patients with heart disease during procedures
BuprenorphineDrowsiness, nausea, vomiting, prolonged and naloxone-resistant effects, may precipitate withdrawal in opioid-dependent patientsLow risk of abuse, resistant to naloxone

Opioid agonist-antagonist drugs offer a unique pharmacological profile, combining partial agonist and antagonist actions. They have a range of clinical uses, with advantages such as limited respiratory depression and lower physical dependence potential. However, their side effects and interactions with other opioids must be carefully considered in clinical practice.

Please note that specific dosages and clinical decisions should be made by healthcare professionals based on individual patient needs and conditions. This article provides an overview of these drugs but should not replace medical guidance.


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