Yes — constipation has been reported as a side effect of Istradefylline in FDA adverse-event reports (FAERS) and product labeling. It is among the more frequently reported events for this medication. These are voluntary reports, so they show what's been reported, not how often it happens.
Reported adverse reactions
ADVERSE REACTIONS The following clinically significant adverse reactions are discussed in greater detail in other sections of the labeling: Dyskinesia [see Warnings and Precautions (5.1) ] Hallucinations / Psychotic Behavior [see Warnings and Precautions (5.2) ] Impulse Control / Compulsive Behaviors [see Warnings and Precautions (5.3) ] The most common adverse reactions (at least 5% and more frequent than placebo) were dyskinesia, dizziness, constipation, nausea, hallucination, and insomnia ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact Kyowa Kirin Inc. at 1-844-768-3544 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The safety of NOURIANZ was evaluated in 734 patients with Parkinson's disease (PD) taking a stable dose of levodopa and a DOPA decarboxylase inhibitor, with or without other PD medications, in four randomized, multicenter, double-blind, placebo-controlled trials 12 weeks in duration (Studies 1, 2, 3 and 4) [see Clinical Studies (14) ] . Of the patient population exposed to NOURIANZ, 50% were male, 32% White, 67% Asian, and the mean age was 65 years (range: 33 to 84 years). Of these patients, 356 received NOURIANZ 20 mg and 378 received NOURIANZ 40 mg. Adverse Reactions Leading to Discontinuation of Treatment The incidence of patients discontinuing for any adverse reaction was 5% for NOURIANZ 20 mg, 6% for NOURIANZ 40 mg, and 5% for placebo. The most frequently reported adverse reaction causing study discontinuation was dyskinesia [see Warnings and Precautions (5.1) ] . Common Adverse Reactions in Pooled Placebo-Controlled Trials Table 1 shows adverse reactions with a frequency of at least 2% in patients treated with NOURIANZ 20 mg or 40 mg once daily. The most common adverse reactions in which the frequency for NOURIANZ was at least 5%, and greater than the incidence on placebo, were dyskinesia, dizziness, constipation, nausea, hallucination, and insomnia. Table 1: Adverse Reactions with an Incidence of at Least 2% in Patients Treated with NOURIANZ, and Greater than on Placebo, in Pooled Studies 1, 2, 3, and 4 Adverse Reactions NOURIANZ 20 mg/day (N=356) % NOURIANZ 40 mg/day (N=378) % Placebo N=426 (%) Nervous system disorders Dyskinesia 15 17 8 Dizziness 3 6 4 Gastrointestinal disorders Constipation 5 6 3 Nausea 4 6 5 Diarrhea 1 2 1 Psychiatric disorders Hallucination Includes hallucinations, hallucinations visual, hallucinations olfactory, hallucinations somatic, hallucinations auditory. 2 6 3 Insomnia 1 6 4 Metabolism and nutrition disorders Decreased appetite 1 3 1 Investigations Blood alkaline phosphatase increased 1 2 1 Blood glucose increased 1 2 0 Blood urea increased 1 2 0 Respiratory, thoracic and mediastinal disorders Upper Respiratory Tract Inflammation 1 2 0 Skin and subcutaneous tissue disorders Rash 1 2 1 6.2 Postmarketing Experience The following adverse reaction has been identified during post approval use of istradefylline outside of the United States. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure: increased libido.
Warnings
WARNINGS AND PRECAUTIONS Dyskinesia: Monitor patients for dyskinesia or exacerbation of existing dyskinesia ( 5.1 ). Hallucinations / Psychotic Behavior: Consider dosage reduction or stopping NOURIANZ if occurs ( 5.2 ). Impulse Control / Compulsive Behaviors: Consider dosage reduction or stopping NOURIANZ if occurs ( 5.3 ). 5.1 Dyskinesia NOURIANZ in combination with levodopa may cause dyskinesia or exacerbate pre-existing dyskinesia. In controlled clinical trials (Studies 1, 2, 3, and 4) [see Clinical Studies (14) ] , the incidence of dyskinesia was 15% for NOURIANZ 20 mg, 17% for NOURIANZ 40 mg, and 8% for placebo, in combination with levodopa. One percent of patients treated with either NOURIANZ 20 mg or 40 mg discontinued treatment because of dyskinesia, compared to 0% for placebo. 5.2 Hallucinations / Psychotic Behavior Because of the potential risk of exacerbating psychosis, patients with a major psychotic disorder should not be treated with NOURIANZ. Consider dosage reduction or discontinuation if a patient develops hallucinations or psychotic behaviors while taking NOURIANZ. In controlled clinical trials (Studies 1, 2, 3, and 4) [see Clinical Studies (14) ] , the incidence of hallucinations was 2% for NOURIANZ 20 mg, 6% for NOURIANZ 40 mg, and 3% for placebo. In patients treated with NOURIANZ 40 mg, 1% discontinued because of hallucinations, compared to 0% for placebo and 0% for patients treated with NOURIANZ 20 mg. The incidence of "abnormal thinking and behavior" (paranoid ideation, delusions, confusion, mania, disorientation, aggressive behavior, agitation, or delirium) reported as an adverse reaction was 1% for NOURIANZ 20 mg, 2% for NOURIANZ 40 mg, and 1% for placebo. 5.3 Impulse Control / Compulsive Behaviors Patients treated with NOURIANZ and one or more medication(s) for the treatment of Parkinson's disease (including levodopa) may experience intense urges to gamble, increased sexual urges, intense urges to spend money, binge or compulsive eating, and/or other intense urges, and the inability to control these urges. In controlled clinical trials (Studies 1, 2, 3 and 4) [see Clinical Studies (14) ] , one patient treated with NOURIANZ 40 mg was reported to have impulse control disorder, compared to no patient on placebo or NOURIANZ 20 mg. In some postmarketing cases, these urges were reported to have stopped when the dose was reduced, or the medication was discontinued. Because patients may not recognize these behaviors as abnormal, it is important for prescribers to specifically ask patients or their caregivers about the development of new or increased gambling urges, sexual urges, uncontrolled spending, binge or compulsive eating, or other urges while being treated with NOURIANZ. Consider dose reduction or discontinuation if a patient develops such urges while taking NOURIANZ [see Adverse Reactions (6.2) ] .
Yes — constipation has been reported as a side effect of Istradefylline in FDA adverse-event reports (FAERS) and/or its labeling. These are voluntary reports, so they show what's been reported, not how often it happens.
How common is constipation with Istradefylline?
constipation is among the more frequently reported events for Istradefylline in FAERS. Reporting volume isn't a true incidence rate — check the prescribing information for documented frequencies.
What should I do if I have constipation while taking Istradefylline?
Don't stop a prescribed medication on your own. Tell your prescriber or pharmacist — they can tell you whether it's expected, whether it needs attention, and what to do next.
Informational only, drawn from FDA adverse-event reporting (FAERS) and labeling — not medical advice, and not proof a medication caused an effect. Talk to your clinician or pharmacist about any side effect.
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