ME is a 76-year-old patient with Parkinson’s disease, type 2 diabetes mellitus, hypertension, and hyperlipidemia. His Parkinson’s disease has progressed over the past several years, and he is currently taking carbidopa/levodopa for management of his motor symptoms.
Over the past month, his family has noticed that he has begun experiencing visual hallucinations. He reports seeing people and animals in his home that are not actually present. Although initially mild, the hallucinations have become more frequent and distressing. To manage the hallucinations, olanzapine (Zyprexa) is initiated.
At baseline, ME’s diabetes is reasonably controlled with an A1C of 7.1%, and his weight is 185 pounds. Over the next several weeks, his family reports that he has developed an increased appetite. At follow-up, his fasting blood glucose readings have increased significantly, his weight has increased to 198 pounds, and his A1C is trending upward.
The healthcare team suspects that olanzapine is contributing to both weight gain and worsening hyperglycemia.
Olanzapine is discontinued, and quetiapine (Seroquel) is initiated at a low dose for management of the hallucinations. Antipsychotic selection is very important and not paying attention to adverse effect profiles can put your patients at risk of adverse effects.
Why Is Seroquel Preferred?
Quetiapine is often preferred over olanzapine in a patient with Parkinson’s disease psychosis for two important reasons (these are excellent nuggets to remember when preparing for baord exams).
1. Less Risk of Worsening Parkinson’s Motor Symptoms
Both olanzapine and quetiapine are atypical antipsychotics, but olanzapine has greater dopamine D2 receptor antagonism. Blocking dopamine receptors can worsen the underlying motor symptoms of Parkinson’s disease, including:
- Bradykinesia
- Rigidity
- Tremor
- Difficulty walking
- Other extrapyramidal symptoms
Quetiapine has relatively lower and more transient dopamine D2 receptor binding and is therefore generally less likely to worsen Parkinsonian motor symptoms. This makes it a more practical antipsychotic option when treatment of psychosis is necessary in a patient with Parkinson’s disease.
2. Lower Metabolic Risk Than Olanzapine
Olanzapine is one of the atypical antipsychotics most strongly associated with:
- Weight gain
- Increased appetite
- Hyperglycemia
- Insulin resistance
- Dyslipidemia
- Increased risk of metabolic syndrome
These adverse effects are particularly concerning in a patient who already has diabetes. Although quetiapine can also cause weight gain and metabolic adverse effects, its metabolic risk is generally lower than that of olanzapine. Therefore, switching from olanzapine to quetiapine may help reduce the likelihood of further worsening of blood glucose control and excessive weight gain.
If you are looking for more information on these antipsychotics, these two podcasts are excellent: Olanzapine and Quetiapine
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