Triglyceride-Mimetic Prodrugs of Buprenorphine Enhance Oral Bioavailability via Promotion of Lymphatic Transport

Buprenorphine (BUP) is a potent opioid analgesic that is widely used for severe pain management and opioid replacement therapy. The oral bioavailability of BUP, however, is significantly limited by first-pass metabolism. Previous studies have shown that triglyceride (TG) mimetic prodrugs of the steroid hormone testosterone circumvent first-pass metabolism by directing drug transport through the intestinal lymphatics, bypassing the liver. The current study expanded this prodrug strategy to BUP. Here different self-immolative (SI) linkers were evaluated to conjugate BUP to the 2 position of the TG backbone via the phenol group on BUP. The SI linkers were designed to promote drug release in plasma. Lipolysis of the prodrug in the intestinal tract was examined via incubation with simulated intestinal fluid (SIF), and potential for parent drug liberation in the systemic circulation was evaluated via incubation in rat plasma. Lymphatic transport and bioavailability studies were subsequently conducted in mesenteric lymph duct or carotid artery-cannulated rats, respectively. TG prodrug derivatives were efficiently transported into the lymphatics (up to 45% of the dose in anaesthetised rats, vs. less than 0.1% for BUP). Incorporation of the SI linkers facilitated BUP release from the prodrugs in the plasma and in concert with high lymphatic transport led to a marked enhancement in oral bioavailability (up to 22-fold) compared to BUP alone. These data suggest the potential to develop an orally bioavailable BUP product which may have advantages with respect to patient preference when compared to current sublingual, transdermal patch or parenteral formulations.

Transdermal buprenorphine for pain management in children

Pain is one of the main symptoms reported by sick children, particularly by those suffering from cancer. Opioids are very useful in controlling this symptom but they are burdened with significant side effects that limit their use in children. Buprenorphine is a strong opioid that, due to its particular pharmacological characteristics, ensures excellent pain relief with fewer side effects than other opioids. The transdermal formulation allows for good pain control associated with optimal compliance by patients and few limitations on daily life. Unfortunately, transdermal buprenorphine use remains off-label for the control of chronic pain in children; therefore, it is desirable that new studies can validate its use in the paediatric population. This review aims to analyse the clinical advantages of transdermal buprenorphine in the paediatric population and the possible side effects registered in daily clinical practice.

A comprehensive review of partial opioid agonists for the treatment of chronic pain

Chronic pain is a common condition that is being increasingly recognized, diagnosed, and treated in a variety of settings. Opioids can be used to treat chronic pain but at the cost of adverse effects and risk of dependence. Recently, there has been a movement to improve analgesic care in the setting of the opioid epidemic and the overprescribing of opioids, causing over-accessibility, dependence, and large numbers of overdose deaths. Opioid-specific receptors, including the μ, δ, κ, and opioid receptor like-1 (ORL-1) receptors, are each 7-transmembrane spanning proteins, which affect the G-protein and β-arrestin cascades. Each opioid class can act differently on the receptors, resulting in full, partial, or antagonizing effects. This comprehensive review looks at different agents in major classes, nonselective and mixed/partial agonists/antagonists, including the nonselective partial agonists, levorphanol and tramadol. Mixed partial agonists/antagonists include buprenorphine, pentazocine, nalbuphine, and butorphanol. Oliceridine is the only current selective partial agonist that agonizes specific pathways to promote analgesic effects and discourage adverse effects.

Pharmacologic pain management at the end of life

Escalating pain is common in the final weeks of life, requiring skilled management to assist patients with a life-limiting illness. Using a cancer model, pharmacologic approaches to treat pain in the final weeks of life are reviewed.