One in five medications used by people older than 65 are prescribed inappropriately in primary care settings, which can cause adverse reactions,
according to a new study published by the journal, PLOS ONE. Researchers defined "inappropriate" as prescriptions that are totally wrong, or prescribed at a dosage that is too high or too low.

The study examined 946 studies dealing with medication and prescription use in settings such as outpatient clinics, general and office practices and primary health care clinics. These papers were whittled down to 19 from the United States and various EU countries for analysis. The average rate of inappropriate prescriptions among people older than 65 was 20.5 percent.

Which meds were the most “inappropriately prescribed”? Pain reliever propoxyphene, with an average of 4.52 percent (though it is no longer available in the United States); the antihypertensive doxazosin, with an average of 3.96 percent; diphenhydramine, which is anantihistamine, has an average of 3.3 percent; and the antidepressant amitriptiline, has an average of 3.2 percent.

Roughly one-third older outpatients develop negative reactions to medication, which researchers say could be avoided if alternative, low-risk medications had been prescribed instead. The body also has a more difficult time processing medications as we age: lower kidney and liver functioning makes it harder for the organs to break down drugs and remove them from our body, “leaving it more vulnerable to toxic accumulations of … medications,” according to the new book “Are Your Prescriptions Killing You?” by Armon B. Neel Jr., Ph.D.

The study suggests developing a computerized support system to help physicians better prescribe medication. It's a good thought considering that America's love affair with meds only stands to grow: Prescription purchases jumped by 39 percent between 1999 and 2009, even though the population only increased by 9 percent during that time period, according to KaiserEDU.

Correction: An earlier version of this post characterized diphenhydramine as a drug used for stomach ailments. It is actually an antihistamine.

Earlier on Huff/Post50:

Loading Slideshow...
  • #5 Stimulants

    While stimulants such as <a href="" target="_hplink">Ritalin and Adderall</a> are highly addictive, abuse among older people is not as widespread as it with young adults. However, illicit stimulants like cocaine are more common. In 2008, <a href="" target="_hplink">63 percent of 118,495 emergency room visits</a> made by those 50 and older involved cocaine. The number of older cocaine users likely increased in the past few years since more than 550,000 adults aged 50 and older <a href="" target="_hplink">reported cocaine use</a>, according to a 2011 report. (<a href="" target="_hplink">Image via Flickr</a>, Alex Dodd)

  • #4 Antidepressants

    While the names are varied -- <a href="" target="_hplink">Prozac, Zoloft and Lexapro</a>, among others -- the effects are similar. Used primarily to treat depression and mood disorders, antidepressants have a slight potential for abuse and addiction. According to a 2010 report from The Drug Abuse Warning Network, antidepressants contributed to <a href="" target="_hplink">8.6 percent of emergency room visits</a> by adults 50 and older.

  • #3 Sedatives

    Most often used to treat anxiety and insomnia, <a href="" target="_hplink">sedatives like Valium and Xanax</a> may become addictive <a href="" target="_hplink">if taken incorrectly, or used too often</a>. The Drug Abuse Warning Network identified sedatives, or depressants, as the pharmaceutical involved in <a href="" target="_hplink">31.8 percent of emergency room visits by older adults</a>. (<a href="" target="_hplink">Image via Flickr</a>, Dean812)

  • #2 Pain Relievers

    Painkillers like Oxycodone, Vicodin and Morphine have a high potential for abuse. According to a Drug Abuse Warning Network report, <a href="" target="_hplink">pain relievers were the type of pharmaceutical</a> most often involved in emergency room visits for post-50s, encompassing 43.5 percent of senior ER visits. The vast majority of painkiller-related ER visits -- 33.9 percent -- involved high-level narcotics, rather than over-the-counter pain relievers.

  • #1 Medical Marijuana

    While many people have medical prescriptions for marijuana use, <a href="" target="_hplink">3 million adults aged 50 and older</a> have illegally used the drug within the past year, according to a 2011 report from The National Survey on Drug Use and Health, a branch of the U.S. Government's Department of Health and Human Services. Out of 4.8 million older adults who used illicit drugs, marijuana use was more common than non-medical use of prescription medicines among the 50 to 59 age range (though the opposite was true for those 60 and older). Marijuana is also far more popular among men than women aged 50 and older.