Muscle cramp is defined as a paroxysmal, involuntary, and painful contraction of skeletal muscle. Cirrhotic patients can encounter with muscle cramp frequently, which might be associated with poor quality of life. Gabapentin can be prescribed for muscle cramp. However, patients with liver cirrhosis have limited access to gabapentin which is metabolized primarily in liver. Pregabalin with a similar mechanism of action to gabapentin undergoes negligible metabolism owing to its improved pharmacokinetic properties. Thus, pregabalin might be a promising therapeutic option for patients with liver cirrhosis who are suffering from muscle cramp and susceptible to drug-induced hepatotoxicity. Therefore, the investigators hypothesize that pregabalin could effectively reduce painful symptoms derived from muscle cramp. In the current study, the investigators are going to evaluate the efficacy and safety of pregabalin by comparing outcomes between two groups (treatment group vs. placebo group).

The investigators are planning to recruit patients with liver cirrhosis and muscle cramp, and collect the baseline clinical and laboratory data during the 4-week run-in period for each subject. After a run-in period, there will be the second step of patient selection to achieve a more homogenous study population. Then, patients will be randomly allocated into the treatment (pregabalin) and placebo (dummy) arms, by a web-based randomization program. After a treatment period (75 mg twice daily during the first 1 week as titration, 150 mg twice daily for 4 weeks as standard dose), the investigators will gather further study information of a standard dose period (150mg twice daily for 4 weeks) from the target population and the study subjects will enter the 1-week tapering period (75mg twice a day) to discontinuation. The primary outcome will be the difference in the frequency of muscle cramps between the run-in and treatment phases. The investigators also intend to assess the response rate, defined as the proportion (%) of patients showing ≥50% reduction in the number of muscle cramps, mean change in the average pain intensity, mean change in the score of the Short Form 36 (SF-36, QualityMetric) health survey questionnaire, mean change in the frequency of muscle cramps during sleep, and mean change in the average cramp threshold frequency by the neurophysiologic study (nerve excitability test) and analyze the reasons for drop-out cases.