Which bolus dose would be most appropriate for alfentanil for Mrs H, considering ideal body weight reduction for dosing?

• A. 4 mg
• B. 12 mg
• C. 9 mg
• D. 7 mg

Answer: (C)

When dosing alfentanil for a bolus, use ideal body weight in patients where actual weight would overestimate the amount needed. This helps avoid giving too much drug in those with obesity, since the distribution and clearance of many opioids align more closely with lean mass than total body weight. Alfentanil acts quickly and has a short duration, so you want enough to blunt the response to induction without causing prolonged sedation or respiratory depression.

A 9 mg bolus aligns with the IBW-based dosing range for an adult patient like Mrs H, providing the needed immediate analgesic effect without overshooting safety margins. Smaller amounts may be insufficient for adequate analgesia during induction, while larger doses increase the risk of oversedation and related complications. Therefore, 9 mg is the most appropriate choice when adjusting dose to ideal body weight.