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The Role for Metyrosine in the Treatment of Patients with Pheochromocytoma and Paraganglioma.

CONTEXT
Treatment of pheochromocytoma and paraganglioma (PPGL) requires pre-intervention titration of alpha- and beta-adrenergic blockade, but patients may still be at risk for complications from catecholamine excess. Metyrosine decreases catecholamine production, making it an attractive therapeutic adjunct for select patients.


EVIDENCE ACQUISITION
A systematic literature review was performed (Ovid Medline and Scopus databases) on December 17, 2019, including studies with humans and original data. Studies with 10 or more patients on metyrosine for PPGL were included. Studies were screened for overlapping populations, and the most comprehensive study was included. The references of included studies were reviewed for additional data. Patient data from our institution between 2000-2015 was also reviewed.


EVIDENCE SYNTHESIS
Metyrosine is well tolerated when used for a short course and can improve intraoperative outcomes in PPGL. Metyrosine should be considered when a difficult PPGL resection is expected (eg, pericardiac paraganglioma or abdominal paraganglioma with great vessel involvement), a large release of catecholamines is anticipated (eg, ablative therapy or chemotherapy), or when standard alpha- and beta-adrenergic blockade are not tolerated or cannot adequately control hypertension. Side effects are generally mild and self-limited, with sedation in a majority of patients. Extrapyramidal side effects are rare but can limit use of metyrosine. Due to its expense and limited availability, metyrosine use should be carefully planned and timed in relation to surgery.


CONCLUSIONS
Metyrosine is a safe addition to traditional alpha-adrenergic and beta-adrenergic blockade and should be considered in those patients with PPGL at high risk for acute release of catecholamines.