In a patient who has taken a large dose of an opioid chronically, which feature of the opioid toxidrome shows the least degree of tolerance compared with analgesia and respiratory depression?

• A Suppression of cough reflex
• B Euphoria
• C Sedation
• D Miosis ✓

Explanation

Tolerance develops unevenly across opioid effects: analgesia, euphoria, sedation and respiratory depression all show substantial tolerance, whereas miosis shows very little. Pinpoint pupils therefore remain a reliable sign of opioid toxicity even in highly tolerant individuals, and naloxone reliably reverses them. Euphoria and sedation are among the first effects to which tolerance develops, and cough suppression also wanes with repeated dosing.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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