While the proportion of adults with severe obesity using prescription opioids initially declines in the months after bariatric surgery, it increases within a matter of years, eventually surpassing pre–surgery rates of patients using the potentially addictive pain medications, according to new research from a National Institutes of Health (NIH)–funded multicenter study led by the University of Pittsburgh Graduate School of Public Health.

The findings – which come from one of the largest, longest–running studies of adults who underwent weight–loss surgery – indicate that improvements in obesity–related pain gained through bariatric surgery are not sufficient to counter the need for pain relief in the years following the procedure.

Results were reported in the journal Surgery for Obesity and Related Diseases.

“Almost half of patients reporting opioid use at the time of surgery reported no such use following surgery. However, among the much larger group of patients who did not report opioid use pre–surgery, opioid use gradually increased throughout seven years of follow–up,” said lead author Wendy C. King, PhD, associate professor of epidemiology at Pitt Public Health. “Thus, post–surgery initiation of opioid use explains this phenomenon.”

Starting in 2006, King and her colleagues followed more than 2,000 patients participating in the NIH–funded Longitudinal Assessment of Bariatric Surgery–2 (LABS–2), a prospective observational study of patients undergoing weight–loss surgery at one of 10 hospitals across the United States.

About 70 percent of the patients underwent Roux–en–Y gastric bypass (RYGB), a surgical procedure that significantly reduces the size of the stomach and changes connections with the small intestine. The majority of the remaining participants had a less invasive procedure, laparoscopic adjustable gastric banding, where the surgeon inserts an adjustable band around the patient’s stomach, lessening the amount of food the stomach can hold.

Before surgery, 14.7 percent of the participants reported regularly taking a prescription opioid. Six months after surgery the prevalence decreased to 12.9 percent, but then it rebounded, progressing to 20.3 percent of participants regularly taking opioids seven years after surgery. Among participants who were not taking opioids at the time of surgery, rates increased from 5.8 percent six months after surgery to 14.2 percent seven years later. Hydrocodone was by far the most commonly reported opioid medication, followed by Tramadol and Oxycodone.

There also was an increase over time in the use of medications typically prescribed for opioid dependence, although use of such medications remained rare, with less than 2 percent of patients using them through the years of follow–up.

Most factors related to substance use disorder that were examined – such as gender, age, income, social support, mental health, smoking, alcohol consumption and illicit drug use – were not related to continued or post–surgery opioid use. However, more pain before surgery, worsening or less of an improvement in pain following surgery, and starting or continuing non–opioid pain–killers were each associated with a higher risk of continuing or starting opioid use after surgery.

Some researchers have hypothesized that opioid use increases following bariatric surgery due to discontinuation of non–steroidal anti–inflammatory drugs (NSAIDs), such as ibuprofen, which are contraindicated post–surgery. However, King and her colleagues found that starting NSAIDs post–surgery was associated with a higher risk of also starting to take opioids, while stopping NSAIDs was associated with lower risk of taking opioids.