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Generic name: macimorelin
Drug class: Growth hormones

Medically reviewed by  A Ras MD.

What is Macrilen?

Macrilen is a prescription medicine that is used to test for growth hormone deficiency.


MACRILEN for oral solution is macimorelin acetate, a synthetic growth hormone secretagogue receptor agonist. Macimorelin acetate is described chemically as D-Tryptophanamide, 2-methylalanyl-N-[(1R)-1-(formylamino)-2-(1H-indol-3-yl)ethyl]-acetate.

The molecular formula for macimorelin acetate is C28H34N6O5 with a molecular weight of 534.6 g/mol.

Figure 1: Chemical structure of macimorelin acetate

Figure 1

Each aluminum pouch of MACRILEN contains 60 mg of macimorelin, equivalent to 68 mg of macimorelin acetate, and the following inactive ingredients: lactose monohydrate, crospovidone, sodium stearyl fumarate, saccharin sodium and colloidal silicon dioxide.

Mechanism of Action

Macimorelin stimulates GH release by activating growth hormone secretagogue receptors present in the pituitary and hypothalamus.

Before taking Macrilen, tell your doctor:

  • If you are allergic to Macrilen; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
  • If you have low levels of hormones like sex hormones or thyroid hormones.
  • If you have had growth hormone treatment within the past 7 days.
  • If you are taking or have recently taken any drugs. There are many drugs that can affect the results of the test. Talk with your doctor and pharmacist to see if any of your drugs can affect the results of the test and when to stop taking them before the test.
  • If you are taking any drugs that can cause a certain type of heartbeat that is not normal (prolonged QT interval). There are many drugs that can do this. Ask your doctor or pharmacist if you are not sure.

This is not a list of all drugs or health problems that interact with this medicine.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Macrilen with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take Macrilen?

  • Tell all of your health care providers that you take Macrilen. This includes your doctors, nurses, pharmacists, and dentists.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using Macrilen while you are pregnant.
  • Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.

How is Macrilen best taken?

Use Macrilen as ordered by your doctor. Read all information given to you. Follow all instructions closely.

  • Your doctor will give Macrilen.
  • Do not eat for at least 8 hours before you take Macrilen.

What do I do if I miss a dose?

  • Call your doctor to find out what to do.

What are the side effects of Macrilen that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • A type of abnormal heartbeat (prolonged QT interval) can happen with Macrilen. Call your doctor right away if you have a fast heartbeat, a heartbeat that does not feel normal, or if you pass out.

What are some other side effects of Macrilen?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if you have any side effects that bother you or do not go away.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out Macrilen?

  • If you need to store Macrilen at home, talk with your doctor, nurse, or pharmacist about how to store it.



  • NDC 0169-1401-01 List: 140101
  • Macrilen™
  • (macimorelin) for oral solution
  • 60 mg
  • Use the Macrilen™ solution within
  • 30 minutes after preparation.
  • Discard any unused Macrilen™ solution.
  • For oral use only.
  • Rx only


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