Ramelteon has a highly variable intersubject pharmacokinetic profile (approximately 100% coefficient of variation in C
max and AUC). As noted above, CYP1A2 is the major isozyme involved in the metabolism of ramelteon; the CYP2C subfamily and CYP3A4 isozymes are also involved to a minor degree.
Effects of Other Drugs on Ramelteon Metabolism
Fluvoxamine (strong CYP1A2 inhibitor)
When fluvoxamine 100 mg twice daily was administered for three days prior to single-dose coadministration of ramelteon 16 mg and fluvoxamine, the AUC
0-inf for ramelteon increased approximately 190-fold, and the C
max increased approximately 70-fold, compared to ramelteon administered alone. Ramelteon should not be used in combination with fluvoxamine. Other less strong CYP1A2 inhibitors have not been adequately studied. Ramelteon should be administered with caution to patients taking less strong CYP1A2 inhibitors
[see Contraindications (4), Drug Interactions (7)].
Rifampin (strong CYP enzyme inducer)
Administration of rifampin 600 mg once daily for 11 days resulted in a mean decrease of approximately 80% (40 to 90%) in total exposure to ramelteon and metabolite M-II, (both AUC
0-inf and C
max) after a single 32 mg dose of ramelteon. Efficacy may be reduced when ramelteon is used in combination with strong CYP enzyme inducers such as rifampin
[see Drug Interactions (7)].
Ketoconazole (strong CYP3A4 inhibitor)
The AUC
0-inf and C
max of ramelteon increased by approximately 84% and 36%, respectively, when a single 16 mg dose of ramelteon was administered on the fourth day of ketoconazole 200 mg twice daily administration, compared to administration of ramelteon alone. Similar increases were seen in M-II pharmacokinetic variables. Ramelteon should be administered with caution in subjects taking strong CYP3A4 inhibitors such as ketoconazole
[see Drug Interactions (7)].
Fluconazole (strong CYP2C9 inhibitor)
The total and peak systemic exposure (AUC
0-inf and C
max) of ramelteon after a single 16 mg dose of ramelteon was increased by approximately 150% when administered with fluconazole. Similar increases were also seen in M-II exposure. Ramelteon should be administered with caution in subjects taking strong CYP2C9 inhibitors such as fluconazole
[see Drug Interactions (7)].
Donepezil
Administration of donepezil 10 mg once daily for 26 days resulted in a mean increase of approximately 100% in overall exposure to ramelteon, (AUC
0-inf) and a mean increase of approximately 87% in maximum exposure to ramelteon (C
max) after a single 8 mg dose of ramelteon. No change was seen in M-II exposure. Patients should be closely monitored when ramelteon is coadministered with donepezil
[see Drug Interactions (7)].
Doxepin
Administration of doxepin 10 mg once daily for 23 days resulted in a mean increase of approximately 66% in overall exposure to ramelteon, (AUC
0-inf) and a mean increase of approximately 69% in maximum exposure to ramelteon (C
max) after a single 8 mg dose of ramelteon. No change was seen in M-II exposure. Patients should be closely monitored when ramelteon is coadministered with doxepin
[see Drug Interactions (7)].
Interaction studies of concomitant administration of ramelteon with fluoxetine (CYP2D6 inhibitor), omeprazole (CYP1A2 inducer/CYP2C19 inhibitor), theophylline (CYP1A2 substrate), dextromethorphan (CYP2D6 substrate), sertraline, venlafaxine, escitalopram, gabapentin, and zolpidem did not produce clinically meaningful changes in either peak or total exposures to ramelteon or the M-II metabolite.
Effects of Ramelteon on Metabolism of Other Drugs
Zolpidem
Administration of ramelteon 8 mg once daily for 11 days resulted in an increase in median T
max of zolpidem by approximately 20 minutes and exposure to zolpidem (both AUC
0-inf and C
max) was unchanged after a single 10 mg dose of zolpidem. Ordinarily zolpidem should not be given in a patient taking ramelteon.
Concomitant administration of ramelteon with omeprazole (CYP2C19 substrate), dextromethorphan (CYP2D6 substrate), midazolam (CYP3A4 substrate), theophylline (CYP1A2 substrate), digoxin (p-glycoprotein substrate), warfarin (CYP2C9 [S]/CYP1A2 [R] substrate), venlafaxine, fluvoxamine, donepezil, doxepin, sertraline, escitalopram, and gabapentin did not produce clinically meaningful changes in peak and total exposures to these drugs.
Effect of Alcohol on Ramelteon
With single-dose, daytime coadministration of ramelteon 32 mg and alcohol (0.6 g/kg), there were no clinically meaningful or statistically significant effects on peak or total exposure to ramelteon. However, an additive effect was seen on some measures of psychomotor performance (i.e., the Digit Symbol Substitution Test, the Psychomotor Vigilance Task Test, and a Visual Analog Scale of Sedation) at some postdose time points. No additive effect was seen on the Delayed Word Recognition Test. Because alcohol by itself impairs performance, and the intended effect of ramelteon is to promote sleep, patients should be cautioned not to consume alcohol when using ramelteon.