1. history of allergy to gabapentin or pregabalin;

2. current use of gabapentin or pregabalin for other indications

3. history of chronic pain or chronic daily use of analgesics; a

4. history of epilepsy, other neurological disorders, cognitive impairment, or severe psychiatric disorders;

5. severe cardiovascular or respiratory diseases;

6. impaired renal function; and a history of drug or alcohol abuse.

7. patients with anticipated prolonged duration of surgery for more than two hours

Preoperative Pregabalin vs Gabapentin in Elderly Undergoing Surgry,Controlled Trial