Washington: Over 10 million Americans are taking pain killers and more than four million are taking them regularly in a given week, according to Boston University study.

Opioids are administered for treatment of moderate to severe pain and are among the most widely prescribed drugs. But its use has also raised concerns about potential abuse.

Despite these concerns, characteristics of opioid use within the non-institutionalized US population are not well known, particularly for recent years.

The researchers conducted a phone survey of randomly selected US households; there were 19,150 subjects aged 18 years or older interviewed from February 1998 through September 2006.

Information was gathered on all prescription and non-prescription medications taken during the preceding seven days. For each recorded medication, information was obtained on reason for use, type of administration, number of days taken in the week before the interview, and total duration of the current use.

The researchers found opioids were used 'regularly' by two percent of those surveyed. An additional 2.9 percent used opioids less frequently. Regular opioid use increased with age, decreased with education level, and was more common in females and in non-Hispanic whites.

The prevalence of regular opioid use increased over time. Among regular users, almost half had been taking opioids for two or more years and nearly one-fifth had been taking opioids for five years or longer.

There was also a much higher prevalence of other medication use among regular opioid users compared to nonusers.

According to the researchers, given the large number of individuals affected, the recent increase in public health concern for safe and effective pain management is appropriate.

These findings will appear in the Aug 31 issue of the journal Pain. IANS