Final answer:
The 73-year-old client diagnosed with liver disease is at the highest risk for a greater effect of the IV medication.
Step-by-step explanation:
The client who is at the highest risk for a greater effect of the IV medication is the 73-year-old client diagnosed with liver disease (option a). Liver disease can impair the metabolism and clearance of medications from the body, resulting in increased drug levels. This can lead to toxicity and an exaggerated response to the IV medication.