A 72-year-old female, weighing 55 kg, with a history of cirrhosis (Child-Pugh B), is admitted to hospital for an infection. The physician orders a stat dose of metronidazole 500 mg IV. Her current medications include lactulose and spironolactone. What adjustment, if any, is needed for the metronidazole dose?

Question: A 72-year-old female, weighing 55 kg, with a history of cirrhosis (Child-Pugh B), is admitted to hospital for an infection. The physician orders a stat dose of metronidazole 500 mg IV. Her current medications include lactulose and spironolactone. What adjustment, if any, is needed for the metronidazole dose?

Answer options:

• No adjustment, administer 500 mg IV. ✅ Reduce the dose to 250 mg IV.
• Increase the dosing interval to every 12 hours.
• Reduce the dose to 250 mg IV and increase the interval to every 12 hours.

Correct answer: Reduce the dose to 250 mg IV.

Explanation: For patients with severe hepatic impairment (Child-Pugh B or C), the dose of metronidazole should be reduced by 50% due to impaired metabolism, especially with single large doses given IV. This reduces the risk of accumulation and neurotoxicity.