Trade Name(s)

  • Macrilen

Ther. Class.
diagnostic agents

Pharm. Class.
growth hormone secretagogue receptor agonists


Diagnosis of adult growth hormone deficiency (AGHD).


Activates growth hormone secretagogue receptors in the pituitary and hypothalamus which stimulates the release of growth hormone.

Therapeutic Effect(s):

Diagnosis of AGHD.


Absorption: Unknown.

Distribution: Unknown.

Metabolism and Excretion: Metabolized in the liver via the CYP3A4 isoenzyme.

Half-life: 4.1 hr.

TIME/ACTION PROFILE (plasma concentrations)

POunknown0.5–1.5 hrunknown


Contraindicated in:

  • None known.

Use Cautiously in:

  • Recent onset hypothalamic disease (potential for a false negative result);
  • BMI >40 k g/m2  (diagnostic effectiveness not established);
  • OB:  Lactation: Safety not established in pregnancy or breast feeding;
  • Pedi:  Safety and effectiveness not established in children.

Adverse Reactions/Side Effects

CNS: dizziness, headache

CV: bradycardia, QTc interval prolongation

GI: diarrhea, ↑ appetite, metallic taste, nausea

Misc: fatigue, ↑ sweating

* CAPITALS indicate life-threatening.
Underline indicate most frequent.



Drug-Natural Products:

 St. John's wort  may ↓ levels and lead to a false positive result; discontinue and allow adequate washout before administering macimorelin.


PO (Adults): 0.5 mg/kg single dose administered to patients who have fasted for ≥8 hr.


Granules for oral solution: 60 mg/pkt


  • Obtain weight prior to preparing dose. Determine BMI prior to starting therapy; safety and diagnostic performance not established with BMI >40 k g/m2 .
  • Monitor patient for adverse reactions during test.

Lab Test Considerations:

May cause false negative test results in recent onset hypothalamic disease.

Potential Diagnoses


  • Adequately replace deficiencies in sex hormones, thyroid hormone and/or glucocorticoids prior to dose of macimorelin.
    • Hold growth hormone for at least 1 wk prior to dose.
  • Dissolve 1 packet in 120 mL for patient weighing <120 kg or 2 packets for patient weighing ≥120 kg in 240 mL of water. Stir for 2–3 min; small amount of undissolved particles will remain. Final concentration 0.5 mg/mL.
    • Determine dose by multiplying patient weight by 0.5 mg/kg. Determine volume of dose by dividing dose by 0.5 mg/mL. Use a syringe without a needle to draw up accurate dose. Transfer volume of solution to drinking glass.
  • PO Administer to patient who fasted for at least 8 hr. Patient must drink entire solution within 30 seconds.
    • Draw venous blood samples for GH determination at 30 min, 45 min, 60 min and 90 min after administration.

Patient/Family Teaching

  • Instruct patient to discontinue growth hormone at least 1 wk before study and to fast for at least 8 hrs before study.
  • Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken.
  • Advise female patient to notify health care professionals if pregnancy is planned or suspected or if breast feeding.

Evaluation/Desired Outcomes

Diagnosis of AGHD.

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