New research suggests that taking prescription amphetamines may raise the risk of developing Parkinson’s disease later. But, the researchers noted that the study did not prove a cause-and-effect relationship and further investigation is warranted. The research was released Feb. 19, and is scheduled to be presented in April at the American Academy of Neurology’s annual meeting in Honolulu.
According to study author Stephen K. Van Den Eeden, a senior investigator at the Division of Research at Kaiser Permanente Northern California, in Oakland, people who reported using Benzedrine or Dexedrine at some point in their lives showed a 60 percent greater chance of developing Parkinson’s compared to those who said they had never taken the medications. Van Den Eeden said, “We already know that there are certain risks of amphetamine use… This is one concern that is unproven, but we need to take into consideration whether the benefits outweigh the known risks, and maybe potential risks.”
Parkinson’s disease is a neurological disorder that is characterized by tremors and muscle rigidity. It may ultimately lead to complete immobility. Dopamine is a neurotransmitter that is deficient in thee brain in a patient with Parkinson’s. Amphetamines affect the release and absorption of dopamine. They are commonly prescribed for the treatment of attention-deficit hyperactivity disorder (ADHD), traumatic brain injuries and a chronic sleep disorder known as narcolepsy. These medications were also being routinely prescribed for weight loss when the research first began.
The study involved 66,348 participants between 1964 and 1973 when they were needed to answer two questions concerning amphetamines. The first asked if the person had ever taken weight-loss drugs in general, while the second asked about the use of Benzedrine and Dexedrine in particular. After 1995, researchers followed up on the participants and found that 1,154 had been diagnosed with Parkinson’s. The mean follow-up period was 38.8 years. Results showed that those who said they had taken Benzedrine or Dexedrine showed a 56% increased risk of being diagnosed with Parkinson’s, those who simply said they had taken weight-loss drugs in general did not.
Because data was self-reported, people may not have provided accurate responses. More importantly, critics of the study say, is that the information was gathered at a single time, leaving the authors unaware of other risk factors that could, over a 40-year period, have modified the patients’ risk of developing Parkinson’s.
According to Dr. Stacy Horn, an assistant professor of clinical neurology at the University of Pennsylvania’s Parkinson’s Disease & Movement Disorders Center in Philadelphia, patients and doctors considering prescription amphetamine use should consider the risk-vs.-benefit ratio. Dr. Horn said, “Someone who failed all the other classic medicines might consider drugs such as amphetamines.” She added, “We need to confirm the science… There needs to be some increased surveillance. We should look at patients that have had an addiction, and see if there’s an increased risk in those populations.”
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