Although there are now more treatment options available for non-motor symptoms in Parkinson’s disease, a lack of evidence on their effectiveness and safety means that more studies and new therapeutic strategies are needed, according to a review study.
The study, “Update on Treatments for Nonmotor Symptoms of Parkinson’s Disease — An Evidence‐Based Medicine Review,” appeared in the journal Movement Disorders.
The International Parkinson and Movement Disorders Society Evidence-Based Committee reviewed research published from 2011 through 2016 on Parkinson’s non-motor symptoms to help physicians select the most effective treatments and provide an update to a 2011 study.
Two online databases were searched, resulting in the inclusion of 37 studies with 20 patients or more. In all of the included studies, treatment lasted a maximum of six months, except for one low-quality safety study, meaning the recommendations do not cover long-term symptom management, the team noted. The studies included pharmacological, surgical, and nonpharmacological interventions, which had to be available in at least one country.
According to their level of evidence, the different approaches were classified as efficacious, likely efficacious, unlikely efficacious, non-efficacious, or with insufficient evidence. To address practice implications, the team also rated the interventions as clinically useful, possibly useful, and unlikely useful, not useful, or investigational.
Christopher G. Goetz, MD, president of the International Parkinson and Movement Disorders Society, noted the differences between this approach and practice guidelines issued by medical associations such as the American Academy of Neurology. In a Neurology Today article written by Susan Fitzgerald, titled “Which are the Most Efficacious Therapies for Nonmotor Parkinson Disease Symptoms?” he said that “guidelines are really culturally based,” and take into account “regulatory issues, access issues, and insurance issues.”
“With evidence-based methodology, we are strictly looking at the published evidence. We don’t tell you whether we recommend it (a specific therapy),” he added.
No clinical trials met the inclusion criteria for the treatment of anxiety disorders, excessive sweating, rapid eye movement behavior disorder, and olfactory or ophthalmologic dysfunction.
Six new studies were reviewed for depression. One addressed venlafaxine, characterized as efficacious, with an acceptable safety risk and no need for specialized monitoring, and clinically useful. This contrasted to amitriptyline, which has insufficient efficacy evidence to treat depression in Parkinson’s patients and was rated as possibly useful. Paroxetine, citalopram, fluoxetine and sertraline, all selective serotonin reuptake inhibitors (SSRIs), were categorized in a similar way.
Rotigotine, marketed as Neupro, was found unlikely efficacious based on the results of one study, and rated as investigational regarding practice implications. Rasagiline, marketed as Azilect, also showed insufficient evidence of efficacy and was classified as investigational as well.
As for nonpharmacological interventions, two studies on repetitive transcranial stimulation showed inconsistent effects on depression. However, its benefits in the general population and in specific measures in people with depression make this approach possibly useful for short-term treatment of Parkinson’s.
Cognitive-behavioral therapy (CBT) could only be rated as likely efficacious and has insufficient safety evidence in the treatment of depression in Parkinson’s due to the lack of replication of its benefits, the investigators cautioned.
Treatments for apathy were also evaluated. Rivastigmine, marketed as Exelon, was found efficacious in one study, but its small group of patients mean that this medication is only possibly useful in the clinic. A similar conclusion was reached for piribedil following deep brain stimulation. In contrast, Neupro was classified as unlikely efficacious based on one trial.
As for the treatment of impulse control disorders, naltrexone, marketed as ReVia, showed insufficient efficacy and safety evidence, while CBT was rated as likely efficacious and possibly useful clinically based on one new study.
Regarding dementia, Aricept (donepezil) and Razadyne (galantamine) still have insufficient efficacy evidence, but were rated possibly useful in clinical practice due to their established benefits outside Parkinson’s.
Both rasagiline and rivastigmine have insufficient efficacy evidence to treat cognitive impairment. A similar conclusion was reached for transcranial direct current stimulation and for cognitive rehabilitation in patients on computer-based cognitive training.
Three new studies were evaluated for psychosis. While olanzapine, marketed as Zyprexa, is not efficacious and therefore not useful from a clinical perspective, Nuplazid (pimavanserin) was characterized as efficacious over six weeks and clinically useful. Seroquel (quetiapine) has insufficient evidence though it is possibly useful in the clinic.
Studies of sleep disorders indicated that Lunesta (eszopiclone) and melatonin have insufficient evidence for the treatment of insomnia, but are possibly useful. Modafinil, marketed as Provigil, is also possibly useful for excessive daytime somnolence and sudden onset of sleep in people with Parkinson’s. Continuous positive airway pressure was considered likely efficacious and possibly useful in lessening daytime sleepiness in patients with obstructive sleep apnea, and Neupro was rated the same for improving sleep quality in Parkinson’s patients.
Assessed treatments of orthostatic hypotension — defined as a drop in blood pressure when standing up — included midodrine and fludrocortisone, marketed as Florinef. Although both have insufficient efficacy evidence, they are classified as possibly useful in the clinic due to benefits seen in clinical trials.
The only trial concerning urinary dysfunction addressed solifenacin, marketed as VESIcare, as a treatment for overactive bladder. It showed that this medication has insufficient evidence on efficacy, but is possibly useful in clinical practice due to benefits observed outside Parkinson’s, while having an acceptable safety risk without specialized monitoring.
One other study addressed erectile dysfunction. Viagra (sildenafil) was considered efficacious and clinically useful, with data in the general population indicating an acceptable safety risk.
Similar efficacy and clinically utility conclusions were presented for botulinum toxin B as a therapy for drooling. Both botulinum toxin type A and B should be administered by well-trained physicians with access to specialized monitoring tools, the researchers emphasized.
Three studies evaluated approaches for gastrointestinal dysfunction. Results of one trial led to lubiprostone, marketed as Amitiza, being considered likely efficacious and possibly useful to treat constipation in people with Parkinson’s. Its safety data in the general and elderly populations indicate that lubiprostone has an acceptable risk in Parkinson’s patients.
Probiotics were categorized as efficacious and clinically useful, which support their over-the-counter use and lack of safety concerns. In contrast, abdominal massages with lifestyle advice have insufficient evidence on safety and efficacy to ease constipation.
Rasagiline was also evaluated as an approach for fatigue, considered efficacious and possible useful based on one small study. One trial analyzed acupuncture in Parkinson’s, but although benefits were found, this approach still has insufficient efficacy evidence.
For pain, prolonged-release oxycodone-naloxone has insufficient evidence, but is possibly useful for Parkinson’s patients with chronic pain, with an acceptable safety risk without specialized monitoring. Rotigotine also has insufficient evidence as a way to lessen pain in Parkinson’s patients, despite benefits seen in one trial.
Overall, despite the substantial growth in the evidence base of approaches for non-motor symptoms in Parkinson’s, this update shows that treatment options remain limited, making the development and testing of new therapies “a top priority,” the team said.
According to Daniel Weintraub, MD, research on Parkinson’s psychiatric and cognitive symptoms is key due to the specificity of the disease compared with the same manifestations found in the general population. He also said this update may help investigators spot areas in need of clinical trials, such as anxiety.
Laura Marsh, MD, a professor of psychiatry and neurology at Baylor College of Medicine, cautioned that although the new review provides “a useful analysis for clinicians to consider,” they still have to practice “the art of medicine.” This involves challenges such as evaluating if dopaminergic therapies for motor function are causing non-motor side effects and what symptom to address first in people with more than one of these complications, she said.