Parkinson’s Medicines Not Much Help in Severe Abdominal Pain
New focus on pain due to impact on patients' quality of life
Medicines for Parkinson’s disease in patients with persistent intolerable abdominal pain showed short and limited usefulness in treating this debilitating non-motor symptom, a study in Japan reported.
Nonetheless, researchers found that Duodopa/Duopa, also known as levodopa/carbidopa intestinal gel (LCIG) or memantine, particularly helped to relieve the pain in one patient. Deep brain stimulation — implanting electrodes in certain brain areas that produce electrical impulses — was effective in another patient.
“Requiring a high dose of levodopa, such as levodopa-carbidopa intestinal gel or deep brain stimulation, is effective for persistent intolerable abdominal pain,” the researchers wrote, noting, however, that the effects can be limited.
While such pain “is likely to be infrequent, it alleviates the quality of life of patients with [Parkinson’s disease],” the team wrote.
Titled “Persistent intolerable abdominal pain in patients with Parkinson’s disease,” the study was published in Clinical Neurology and Neurosurgery. The small study was conducted by two researchers at the Nara Medical University, in Japan.
Most Parkinson’s medicines of little use against pain
Parkinson’s non-motor symptoms, including pain associated with muscle or joint rigidity, are gaining more attention due to the impact they have on a patient’s day-to-day living, namely by decreasing quality of life.
Abdominal pain has been reported among some Parkinson’s disease patients, with an estimated occurrence of 3.7% in one study. Patients with this type of pain have been found to have difficulties in living their daily life.
Moreover, abdominal pain in Parkinson’s patients can result from a gradual reduction of levodopa dose over time, also called dose wearing-off, common after about 5–6 years of levodopa use. Levodopa is a Parkinson’s therapy used to treat movement stiffness and slowness.
“The pathophysiology [the processes associated with disease] of such abdominal pain has not been confirmed. Thus, we clinically studied patients with [Parkinson’s disease] and persistent intolerable abdominal pain to determine the pathophysiology and effective therapy,” the researchers wrote.
The team collected clinical information from six Parkinson’s patients, ages 71–85. There were three men and three women. All patients had recurrent intolerable abdominal pain from 2006 to 2022.
Mean duration of levodopa intake before the onset of abdominal pain was six years, and the mean daily equivalent dose was 636.7 mg/day.
Overall, the abdominal pain in the six patients analyzed occurred in the lower abdomen, with powerful pulling, muscle construction or crump, squeezed feeling, or a combination of all. Two patients also experienced pain in their legs.
The pain was felt daily and often during the night, but no relationship was found with the timing of eating food/meals. Abdominal pain led to a decrease in the amount of food eaten and a reduced body weight in some patients. Pain in two of the patients was associated with dose wearing-off.
Researchers observed a mild reduction of pain after the levodopa equivalent daily dose was increased in five of the six patients. However, this effect was limited.
The therapeutic usefulness of antiparkinsonian medications, including levodopa and long-acting dopamine agonists, is short and limited for intolerable abdominal pain.
The infusion of mepivacaine or lidocaine to the rectus muscles of the abdomen in two patients, apomorphine, etizolam, or tramadol in one other showed limited effectiveness, namely a mild reduction of abdominal pain but that did not persist.
Rasagiline — a therapy used to increase the levels of dopamine in the brain — was moderately effective in one of the patients; its effects were maintained for 10 months.
In another patient, treatment with Duodopa/Duopa for several weeks also had moderate effectiveness, and with memantine, a pain-free result was observed.
Deep brain stimulation in another patient also resulted in pain relief in both the abdomen and legs.
Moreover, a CT scan of the patients’ abdomen showed a maximal thickness in those with abdominal pain at the level of the lumbar vertebras 4 (L4) and 5 (L5) to be significantly higher (mean of 12.4 mm at L4 and 12.6 mm at L5) than in Parkinson’s patients without pain (8.0 mm at L4 and 8.2 mm at L5).
“The hypertrophy of the rectus abdominis muscle might be derived from persistent muscle contractions,” the researchers wrote. The team suggests this could be a sign of a dystonia, a movement disorder that causes muscles to contract involuntarily.
“In conclusion, the therapeutic usefulness of antiparkinsonian medications, including levodopa and long-acting dopamine agonists, is short and limited for intolerable abdominal pain,” the researchers wrote.
According to the team, the cause of abdominal pain “seems to vary, and our observations found wearing-off of related pain and muscle contraction” as potential causes.
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