Common Prescribing errors in primary care when managing Parkinson’s disease patients

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There have been several incidences of the Ropinirole starter pack being requested by primary care. Over a 28 day period the drug is titrated up from zero to 1mg TDS, and GP surgeries have erroneously put this drug on repeat prescription, so the patient starts a cycle of zero to 1mg TDS Ropinirole every 28 days, which often causes unwanted side effects.

There have also been a number of dosing errors when prescribers have been switching between the base and salt of Pramipexole. To date I have encountered three patients prescribed large overdoses of the dopamine agonist causing significant side effects and two hospital admissions.

Another area that causes prescribing problems is when a Parkinson’s disease patient prescribed the monoamine oxidase B inhibitor, Rasagiline, requires an antidepressant. The use of Fluoxetine or Fluvoxamine should be avoided in view of the risk of developing serotonin syndrome as a serious side effect. Rasagiline trials however have demonstrated that doses of Amitriptyline up to 50mg a day, Citalopram up to 20mg a day, Sertraline up to 100mg a day and Paroxetine up to 30mg a day were all relatively safe with no reported cases of serotonin syndrome. Cough and cold remedies containing sympathomimetics should also be avoided with the monoamine oxidase B inhibitors.

I have observed a number of problems with Parkinson’s disease patients being prescribed dopamine blocking drugs in primary care which have made their Parkinson’s symptoms worse.

Examples of drugs to be avoided by patients diagnosed with Parkinson’s disease:

Listed below and in the table are typical examples of drugs to be avoided when patients present with additional symptoms:

For hallucinations/confusion – avoid Chlorpromazine, Fluphenazine, Perphenazine, Trifluoperazine, Flupenthixol and Haloperidol. If an antipsychotic is necessary then low dose Quetiapine can be prescribed or Clozapine could be considered if the necessary monitoring is available.

For nausea and vomiting – avoid Metoclopramide and Prochlorperazine. If an antiemetic is required, Domperidone, Cyclizine or Ondansetron are better alternatives.

Vigilance is also required with the use of antihistamines, antidepressants and antihypertensives e.g., calcium channel blockers.

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A specific case study:

A 62 year old female was diagnosed with idiopathic Parkinson’s disease by a Consultant Neurologist in Secondary Care following blood tests, which were all returned as normal (routine full blood counts and thyroid function tests are performed to eliminate a blood or thyroid imbalance causing Parkinson’s like symptoms and also to check ceruloplasmin and copper levels in the blood, to rule out the possibility that Wilson’s disease could be contributing to any presenting symptoms. Once these bloods have been returned as normal we would continue to manage the symptoms as those of Parkinson’s disease). Her symptoms were slowness of gait and bradykinesia and rigidity of the right hand side. She also had an infrequent rest tremor on the right hand side. Following diagnosis she was started on Co-careldopa 62.5mg and this was gradually uptitrated to 125mg TDS. Over the next 12 months she was initiated on Ropinirole XL 4mg OD and Rasagiline 1mg OD. The Consultant overseeing her care had not been informed that she had been prescribed Prochlorperazine 5mg TDS for giddiness for many years. The patient was scheduled for a review in the community Parkinson’s disease clinic and asked to bring all her medication with her. At this point the Prochlorperazine was identified and discontinued. Within weeks her symptoms started to improve and all her Parkinson’s disease medication was slowly reduced and eventually discontinued.

This case highlights the importance of obtaining a full and correct patient history and also ensuring that any dopamine blocking drugs are discontinued if clinically appropriate to do so.