Metyrosine

Mechanism-of-action classes: Catecholamine Synthesis Inhibitors; Enzyme Inhibitors.

• Metyrosine capsules are indicated in the treatment of patients with pheochromocytoma for: 1. Preoperative preparation of patients for surgery.

• Metyrosine capsules are contraindicated in persons known to be hypersensitive to this compound.contraindicated

The recommended initial dosage of metyrosine capsules for adults and children 12 years of age and older is 250 mg orally four times daily. This may be increased by 250 mg to 500 mg every day to a maximum of 4 g/day in divided doses. When used for preoperative preparation, the optimally effective dosage of metyrosine capsules should be given for at least five to seven days. Optimally effective dosages of metyrosine capsules usually are between 2 g/day and 3 g/day, and the dose should be titrated by monitoring clinical symptoms and catecholamine excretion. In patients who are hypertensive, dosage should be titrated to achieve normalization of blood pressure and control of clinical symptoms. In patients who are usually normotensive, dosage should be titrated to the amount that will reduce urinary metanephrines and/or vanillylmandelic acid by 50% or more. If patients are not adequately controlled by the use of metyrosine capsules, an alpha-adrenergic blocking agent (phenoxybenzamine) should be added. Use of metyrosine capsules in children under 12 years of age has been limited and a dosage schedule for this age group cannot be given.

Maintain Fluid Volume During and After Surgery When metyrosine is used preoperatively, alone or especially in combination with alpha-adrenergic blocking drugs, adequate intravascular volume must be maintained intraoperatively (especially after tumor removal) and postoperatively to avoid hypotension and decreased perfusion of vital organs resulting from vasodilatation and expanded volume capacity. Following tumor removal, large volumes of plasma may be needed to maintain blood pressure and central venous pressure within the normal range. In addition, life-threatening arrhythmias may occur during anesthesia and surgery, and may require treatment with a beta-blocker or lidocaine. During surgery, patients should have continuous monitoring of blood pressure and electrocardiogram. Intraoperative Effects While the preoperative use of metyrosine in patients with pheochromocytoma is thought to decrease intraoperative problems with blood pressure control, metyrosine does not eliminate the danger of hypertensive crises or arrhythmias during manipulation of the tumor, and the alpha-adrenergic blocking drug, phentolamine, may be needed. Interaction with Alcohol Metyrosine may add to the sedative effects of alcohol and other CNS depressants, e.g., hypnotics, sedatives, and tranquilizers (see PRECAUTIONS, Information for Patients and Drug Interactions ).

Central Nervous System Sedation The most common adverse reaction to metyrosine is moderate to severe sedation, which has been observed in almost all patients. It occurs at both low and high dosages. Sedative effects begin within the first 24 hours of therapy, are maximal after two to three days, and tend to wane during the next few days. Sedation usually is not obvious after one week unless the dosage is increased, but at dosages greater than 2000 mg/day some degree of sedation or fatigue may persist. In most patients who experience sedation, temporary changes in sleep pattern occur following withdrawal of the drug. Changes consist of insomnia that may last for two or three days and feelings of increased alertness and ambition. Even patients who do not experience sedation while on metyrosine may report symptoms of psychic stimulation when the drug is discontinued. Extrapyramidal Signs Extrapyramidal signs such as drooling, speech difficulty, and tremor have been reported in approximately 10% of patients. These occasionally have been accompanied by trismus and frank parkinsonism. Anxiety and Psychic Disturbances Anxiety and psychic disturbances such as depression, hallucinations, disorientation, and confusion may occur. These effects seem to be dose-dependent and may disappear with reduction of dosage. Diarrhea Diarrhea occurs in about 10% of patients and may be severe. Anti-diarrheal agents may be required if continuation of metyrosine is necessary.

Pregnancy Animal reproduction studies have not been conducted with metyrosine. It is also not known whether metyrosine can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Metyrosine should be given to a pregnant woman only if clearly needed.

Signs of metyrosine overdosage include those central nervous system effects observed in some patients even at low dosages. At doses exceeding 2000 mg/day, some degree of sedation or feeling of fatigue may persist. Doses of 2000 mg/day to 4000 mg/day can result in anxiety or agitated depression, neuromuscular effects (including fine tremor of the hands, gross tremor of the trunk, tightening of the jaw with trismus), diarrhea, and decreased salivation with dry mouth. Reduction of drug dose or cessation of treatment results in the disappearance of these symptoms. The acute toxicity of metyrosine was 442 mg/kg and 752 mg/kg in the female mouse and rat respectively.

• Oct 3, 1979NDANDA017871Bausch
• Jul 24, 2020ANDAANDA213734Amneal
• Apr 9, 2025ANDAANDA218620Dr Reddys Labs Sa

1. 1Off Label Use1418%
2. 2Somnolence1114%
3. 3Diarrhoea67.9%
4. 4Pneumonia67.9%
5. 5Pyrexia67.9%
6. 6Malaise56.6%
7. 7Drug Ineffective45.3%
8. 8Hospitalisation45.3%
9. 9Vomiting45.3%
10. 10Blood Pressure Increased33.9%
11. 11Constipation33.9%
12. 12Delirium33.9%
13. 13Dizziness33.9%
14. 14Fatigue33.9%
15. 15Hypoglycaemia33.9%

Recent PubMed references pinned to Metyrosine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

• Enhanced tumor retention of the novel LAT1-targeting PET probe [(18)F]FAMT-OMe: A comparative study with [(18)F]FAMT in glioma mouse models.
  Nuclear medicine and biology · 2026 · Sampunta T, Watabe T, Naka S, et al.
  PMID 41855739DOI 10.1016/j.nucmedbio.2026.109623
• Alpha-methyl-para-tyrosine and amphetamine ameliorate hyperactivity in a novel mouse model of dopamine transporter deficiency syndrome.
  EMBO molecular medicine · 2026 · Russo EE, Rezayof A, Wallace C, et al.
  PMID 41699258DOI 10.1038/s44321-026-00381-0
• Physiological and metabolic effects of short-term dopamine reduction in healthy horses using a tyrosine hydroxylase inhibitor (alpha-methyl-para-tyrosine).
  Domestic animal endocrinology · 2025 · Galinelli NC, Bamford NJ, Erdody ML, et al.
  PMID 39388740DOI 10.1016/j.domaniend.2024.106891
• Stress-Related Chronic Fatigue Syndrome: A Case Report with a Positive Response to Alpha-Methyl-P-Tyrosine (AMPT) Treatment.
  International journal of molecular sciences · 2024 · Ljungström M, Oltra E, Pardo M, et al.
  PMID 39063020DOI 10.3390/ijms25147778
• The combination of doxazosin and metyrosine as a preoperative treatment for pheochromocytomas and paragangliomas.
  Endocrine · 2024 · Ohmachi Y, Yamamoto M, Inaba Y, et al.
  PMID 38206436DOI 10.1007/s12020-023-03681-4
• The Role for Metyrosine in the Treatment of Patients With Pheochromocytoma and Paraganglioma.
  The Journal of clinical endocrinology and metabolism · 2021 · Gruber LM, Jasim S, Ducharme-Smith A, et al.
  PMID 33693908DOI 10.1210/clinem/dgab130
• α-Emitting cancer therapy using (211) At-AAMT targeting LAT1.
  Cancer science · 2021 · Kaneda-Nakashima K, Zhang Z, Manabe Y, et al.
  PMID 33277750DOI 10.1111/cas.14761
• Blockade of the dopaminergic neurotransmission with AMPT and reserpine induces a differential expression of genes of the dopaminergic phenotype in substantia nigra.
  Neuropharmacology · 2020 · Ortiz-Padilla S, Soto-Orduño E, Barrios ME, et al.
  PMID 31870855DOI 10.1016/j.neuropharm.2019.107920

The 10 most recently updated of 18 ClinicalTrials.gov registrations naming Metyrosine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• SM-88 Maintenance Therapy for Advanced Ewing's Sarcoma and as Salvage Therapy for Sarcoma
  Active not recruiting · Phase 2 · Interventional · 31 enrolled · Sarcoma Oncology Research Center, LLC
  NCT03778996updated 2025-02-24
• A Randomized Phase 2/3 Multi-Center Study of SM-88 in Participants With Metastatic Pancreatic Cancer
  Terminated · Phase 2 · Phase 3 · Interventional · 130 enrolled · Tyme, Inc
  NCT03512756updated 2024-11-06
• Safety of L1-79 in Adolescent and Adult Males With Autism
  Completed · Phase 2 · Interventional · 42 enrolled · Yamo Pharmaceuticals LLC
  NCT02947048updated 2024-08-21
• A 12-Week Crossover Study to Assess the Efficacy, Safety and Tolerability of L1-79 in Subjects Aged 12-21 Years With Autism Spectrum Disorder
  Completed · Phase 2 · Interventional · 58 enrolled · Yamo Pharmaceuticals LLC
  NCT05067582updated 2024-07-31
• Oral SM-88 in Patients With Metastatic HR+/HER2- Breast Cancer
  Terminated · Phase 2 · Interventional · 11 enrolled · Georgetown University
  NCT04720664updated 2023-08-28
• Understanding Dopamine Mechanisms in Cocaine Addiction Using AMPT and Methylphenidate With [11C]RAC/[11C]PHNO PET
  Terminated · Interventional · 1 enrolled · Yale University
  NCT02152670updated 2023-02-16
• Study of SM-88 in Advanced Cancers
  Withdrawn · Phase 1 · Phase 2 · Interventional · 0 enrolled · Tyme, Inc
  NCT02562612updated 2022-07-01
• Intraoperative Carbetocin to Decrease Blood Loss During Hysteroscopic Myomectomy
  Completed · Phase 4 · Interventional · 40 enrolled · Mansoura University Hospital
  NCT04482959updated 2022-04-06
• Metyrosine (Demser®) for the Treatment of Psychotic Disorders in Patients With Velocardiofacial Syndrome
  Terminated · Phase 2 · Interventional · 2 enrolled · Bausch Health Americas, Inc.
  NCT01127503updated 2019-11-22
• Study of the Efficacy, Safety, and Pharmacokinetics of SM88 in Patients With Prostate Cancer
  Completed · Phase 1 · Phase 2 · Interventional · 23 enrolled · Tyme, Inc
  NCT02796898updated 2019-07-22

Frequently asked questions

How does Metyrosine work?

Mechanism-of-action classes: Catecholamine Synthesis Inhibitors; Enzyme Inhibitors.

What is Metyrosine used for?

According to FDA labeling, Metyrosine carries indications including: Metyrosine capsules are indicated in the treatment of patients with pheochromocytoma for: 1. Preoperative preparation of patients for surgery.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Metyrosine?

Metyrosine is classified as Tyrosine hydroxylase inhibitors, Catecholamine Synthesis Inhibitor, Catecholamine Synthesis Inhibitors, Enzyme Inhibitors, Decreased Epinephrine Activity, Decreased Norepinephrine Activity.

What are the brand names for Metyrosine?

Metyrosine is marketed under brand names including Demser.

What are the contraindications for Metyrosine?

Metyrosine labeling lists contraindications including: Metyrosine capsules are contraindicated in persons known to be hypersensitive to this compound.. Always consult the full prescribing information and a clinician.