Question

All of the following are true about spinal (intrathecal) opioids EXCEPT?

• A. Acts on dorsal horn substantia gelatinosa
• B. Can cause itching
• C. Intestinal motility is decreased
• D. Can cause respiratory depression

Hint:

Three are classic neuraxial opioid effects; which gut effect is the odd one out at intrathecal doses?

Answer 1

The Correct Option is C

Step 1: This is a negative ("all except") question, so we identify the one statement that is NOT a recognised feature of spinal opioids.
Step 2: Spinal opioids act at the substantia gelatinosa (Rexed lamina II) of the dorsal horn, binding presynaptic and postsynaptic opioid receptors to inhibit nociceptive transmission. Statement A is true.
Step 3: Pruritus (itching) is one of the most common side effects of intrathecal opioids, classically affecting the face and trunk and mediated centrally rather than by histamine. Statement B is true.
Step 4: Respiratory depression, including delayed depression from rostral cephalad spread of the drug in the CSF, is a well known and serious complication. Statement D is true.
Step 5: The intended exception is statement C. Because intrathecal opioids are given in very small doses and act predominantly at the spinal cord with limited systemic absorption, a clinically significant decrease in intestinal motility (ileus) is not a typical feature compared with systemic opioids. Hence within this exam it is taken as the untrue option.
Conclusion: The exception is "intestinal motility is decreased" (option 3), matching the printed key.