Which opioid is noted for anticholinergic properties and is sometimes described as the 'weird uncle' of the opioid family?

Which opioid is noted for anticholinergic properties and is sometimes described as the 'weird uncle' of the opioid family?

• A. Morphine
• B. Fentanyl
• C. Sufentanil
• D. Meperidine

Answer: (D)

Anticholinergic activity in an opioid means it can block acetylcholine at muscarinic receptors, leading to effects like tachycardia, dry mouth, urinary retention, and decreased GI motility. One opioid stands out for this property and is often described as the oddball in the opioid family because of these antimuscarinic effects. That drug is meperidine. Its anticholinergic action explains the tachycardia and other autonomic effects you can see with it, which differentiates it from the others listed. Meperidine also has a notable caveat: its metabolite normeperidine can accumulate, especially in renal impairment or with high doses, and can provoke CNS excitation and seizures. This risk helps explain why meperidine is used less commonly for routine analgesia compared with morphine, fentanyl, or sufentanil, which are mu-opioid agonists with minimal anticholinergic effects. So the description points to the opioid with anticholinergic properties—the one often referred to as the weird uncle of the opioid family: meperidine.

Anticholinergic activity in an opioid means it can block acetylcholine at muscarinic receptors, leading to effects like tachycardia, dry mouth, urinary retention, and decreased GI motility. One opioid stands out for this property and is often described as the oddball in the opioid family because of these antimuscarinic effects. That drug is meperidine. Its anticholinergic action explains the tachycardia and other autonomic effects you can see with it, which differentiates it from the others listed.

Meperidine also has a notable caveat: its metabolite normeperidine can accumulate, especially in renal impairment or with high doses, and can provoke CNS excitation and seizures. This risk helps explain why meperidine is used less commonly for routine analgesia compared with morphine, fentanyl, or sufentanil, which are mu-opioid agonists with minimal anticholinergic effects.

So the description points to the opioid with anticholinergic properties—the one often referred to as the weird uncle of the opioid family: meperidine.