BALTIMORE—Amitriptyline decreased pain and improved function significantly more than did pregabalin in a randomized trial of patients with chronic low back pain, according to a study presented at the 139th Annual Meeting of the American Neurological Association.
Almost 60% of patients taking the tricyclic antidepressant experienced at least a 50% decrease in pain on a visual analog pain scale, compared with 38% of those taking pregabalin, reported Jayantee Kalita, MD.
The study is the first to examine amitriptyline in low back pain, a chronic pain condition that can be debilitating in its duration and severity and is difficult to control, said Dr. Kalita, a neurologist at the Sanjay Gandhi Post Graduate Institute of Medicine, Lucknow, India.
A 2011 systematic review found 17 randomized controlled trials of pharmacologic treatments for chronic low back pain. These trials examined the benefits of nonsteroidal anti-inflammatory drugs, antidepressants, and opioids. The best results were obtained with acetaminophen and opioids, but dose-limiting side effects occurred, and pain rebounded when the treatment was discontinued. The studies that examined antidepressants found them to be no more effective than placebo.
Dr. Kalita and her colleagues randomized 200 patients with chronic low back pain to amitriptyline or pregabalin for 14 weeks. Amitriptyline was started at 10 mg once per day and increased to a maximum of 50 mg as needed. Pregabalin was started at 75 mg twice per day and increased to a maximum of 300 mg twice a day if needed.
The cohort had a mean age of 41, with a median 35 months of back pain, although one patient had experienced 30 years of back pain. Pain was idiopathic and experienced as radiculopathy (48%), localized (46%), or as lower crossed syndrome (6%). Most patients (115) lived in rural areas. Risk factors included diabetes (nine patients), hypertension (15), smoking (39), and tobacco use (65). At baseline, both treatment groups reported their pain as a median of 7 on a 10-point visual analog scale. The mean score on the Oswestry Disability Index (ODI) was 40%, indicating severe pain that limits work, travel, personal care, social life, sexual activity, and sleep. At six weeks, pain scores in the amitriptyline group had decreased from 7 to 4, a significant improvement. By the end of 14 weeks, scores had decreased to about 3, which was significantly better than the scores at six weeks and at baseline.
In the pregabalin group, the pain score decreased from 7 to 5, which was not a significant change. During weeks six to 14, scores decreased another half-point, to around 4.5. This was a significant improvement from baseline, but not from week six. The ODI score also improved more in patients taking amitriptyline. From a median of about 43%, the index decreased to about 30% at six weeks and 20% at 14 weeks. A 20% score indicates minimal disability; patients need no assistance with activities of daily living and experience minimal life interruptions from pain.
Disability also improved in the pregabalin group, decreasing from about 40% at baseline to 35% at six weeks, and then to about 25% at 14 weeks. This score falls in the moderate disability range. Patients may need help with some daily activities and may be off work. The final score was also a significant improvement over baseline, although it was not as robust as with the amitriptyline group, Dr. Kalita noted.
In the intent-to-treat analysis, 57% of the amitriptyline group and 39% of the pregabalin group experienced a pain scale decrease of at least 50%. There was at least a 20% improvement in the disability scores of 67% of the amitriptyline group and 48% of the pregabalin group.
Side effects included sedation, vertigo, dry mouth, skin rash, and restlessness. Significantly more patients who took pregabalin had at least one side effect (eight patients vs three patients). Sedation was most common, occurring in 10 patients who took amitriptyline and four who took pregabalin.
—Michele G. Sullivan