Macrilen (Page 2 of 4)


7.1 Drugs that Prolong QT Interval

Co-administration of MACRILEN with drugs that prolong the QT interval (such as antipsychotic medications (e.g., chlorpromazine, haloperidol, thioridazine, ziprasidone), antibiotics (e.g., moxifloxacin), Class 1A (e.g., quinidine, procainamide) and Class III (e.g., amiodarone, sotalol) antiarrhythmic medications or any other medications known to prolong the QT interval) may lead to development of torsade de pointes-type ventricular tachycardia. Avoid concomitant use of MACRILEN with drugs that prolong the QT interval. Sufficient washout time of drugs that are known to prolong the QT interval prior to administration of MACRILEN is recommended [see Dosage and Administration (2.2) and Warnings and Precautions (5.1)].

7.2 Cytochrome P450 (CYP) 3A4 Inducers

Co-administration of a strong CYP3A4 inducer with MACRILEN (e.g., carbamazepine, enzalutamide, mitotane, phenytoin, rifampin, St. John’s wort, bosentan, efavirenz, etravirine, modafinil, armodafinil, rufinamide) may reduce the plasma macimorelin concentrations and may lead to false positive test results. Discontinue strong CYP3A4 inducers prior to MACRILEN use. Sufficient washout time of strong CYP3A4 inducers prior to administration of MACRILEN is recommended [see Dosage and Administration (2.2) and Warnings and Precautions (5.2)].

7.3 Drugs Affecting Growth Hormone Release

The following drugs may impact the accuracy of the MACRILEN diagnostic test. Avoid concomitant use of MACRILEN with the following [see Dosage and Administration (2.2)]:

Drugs that directly affect the pituitary secretion of growth hormone (such as somatostatin, insulin, glucocorticoids, and cyclooxygenase inhibitors such as aspirin or indomethacin).
Drugs that may transiently elevate growth hormone concentrations (such as clonidine, levodopa, and insulin).
Drugs that may blunt the growth hormone response to MACRILEN (such as muscarinic antagonists: atropine, anti-thyroid medication: propylthiouracil, and growth hormone products). Discontinue growth hormone products at least one week before administering the MACRILEN diagnostic test.

Sufficient washout time of drugs affecting growth hormone release prior to administration of MACRILEN is recommended.


8.1 Pregnancy

Risk summary

There are no available data with MACRILEN use in pregnant women to inform a drug associated risk for adverse developmental outcomes. Animal reproduction studies have not been conducted with MACRILEN. MACRILEN is indicated as a single dose which limits the risk of adverse developmental outcomes from exposure to MACRILEN.

The estimated background risk of major birth defects and miscarriage for the indicated populations is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 – 4% and 15 – 20%, respectively.

8.2 Lactation

Risk Summary

There are no data on the presence of macimorelin in human or animal milk, the effects on the breastfed infant or the effects on milk production. The lack of clinical data during lactation precludes a clear determination of the risk of MACRILEN to an infant during lactation; therefore, the developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for MACRILEN and any potential adverse effects on the breastfed infant from MACRILEN or the underlying maternal condition.

8.4 Pediatric Use

The safety and efficacy of MACRILEN in pediatric patients have not been established.

8.5 Geriatric Use

Growth hormone secretion normally decreases with age. Therefore, elderly subjects might require a lower cut-off point for diagnosis of adult growth hormone deficiency. Clinical studies of MACRILEN did not include a sufficient number of subjects aged 65 and over to determine whether elderly patients respond differently from younger subjects.


In the event of an overdose, symptomatic and supportive measures should be employed.


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 C28 H34 N6 O5 with a molecular weight of 534.6 g/mol.

Figure 1: Chemical structure of macimorelin acetate

Figure 1
(click image for full-size original)

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.


12.1 Mechanism of Action

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

12.2 Pharmacodynamics

GH stimulation

Maximum GH levels are observed between 30 to 90 minutes after administration of MACRILEN.

Cardiac electrophysiology

The effects of macimorelin on ECG parameters were investigated in a dedicated Thorough QT study that investigated in a 3-way cross-over design with 60 healthy subjects the effects of a supra-therapeutic dose of macimorelin (2 mg/kg) (4 times the recommended dosage) in comparison with placebo and with moxifloxacin. This study showed a mean baseline- and placebo-adjusted change (upper single-sided 95% confidence interval) in QTcF of 9.6 msec (11.4 msec) at 4 h post-dose, which occurred after the mean maximum macimorelin plasma concentration (0.5 h). A similar increase in the QTcF interval was also observed in a single-ascending dose study, which included three dose levels (0.5 mg/kg, and 1 mg/kg and 2 mg/kg (2 times and 4 times the recommended dosage, respectively). All three dose levels studied showed a similar magnitude of QTcF prolongation in the Thorough QT study, suggesting an absence of dose dependent changes. The mechanism for the observed QTcF prolongation is unknown [see Warnings and Precautions (5.1)].

12.3 Pharmacokinetics

The mean plasma macimorelin concentrations are similar between patients with AGHD and healthy subjects for 1.5 hours following administration of a single oral dose of 0.5 mg macimorelin/kg body weight.


The maximum plasma macimorelin concentrations (Cmax ) were observed between 0.5 hour and 1.5 hours following oral administration of 0.5 mg macimorelin/kg body weight to patients with AGHD under fasting for at least 8 hours. A liquid meal decreased the macimorelin Cmax and AUC by 55% and 49%, respectively.


An in vitro human liver microsomes study showed that CYP3A4 is the major enzyme to metabolize macimorelin.

Macimorelin was eliminated with a mean terminal half-life (T1/2 ) of 4.1 hours following administration of a single oral dose of 0.5 mg macimorelin/kg body weight in healthy subjects.


13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility


Long-term carcinogenesis studies in rodents have not been conducted.


Macimorelin did not cause mutations in bacteria under assay conditions with or without metabolic activation. There were also no mutations or clastogenic effects in mouse lymphoma cells with or without metabolic activation.

Impairment of Fertility

No studies have been conducted to assess the effect of macimorelin on fertility.

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