Clinical Pharmacology for Igalmi
Mechanism Of Action
Dexmedetomidine is an alpha-2 adrenergic receptor agonist. The mechanism of action of IGALMI in the acute treatment of agitation associated with schizophrenia or bipolar I or II disorder is thought to be due to activation of presynaptic alpha-2 adrenergic receptors.
Pharmacodynamics
Dexmedetomidine acts as an agonist at alpha-2 adrenergic receptors with binding affinities (Ki values) of 4 to 6 nM at the alpha-2 adrenergic receptor subtypes.
Cardiac Electrophysiology
IGALMI exhibits a concentration dependent QT prolongation. Table 4 shows the mean (upper 90% confidence interval) QTcF increase from baseline for respective dosing regimens [see WARNINGS AND PRECAUTIONS].
Table 4: QTcF Increase from Baseline by Dosage of IGALMI
| IGALMI Dosage |
Mean QTcF Increase from Baseline (upper 90% confidence interval) |
| 120 mcg single use |
6 (7) msec |
| 120 mcg + 2 additional doses of 60 mcg 2 hours apart (total 3 doses) |
8 (9) msec |
| 180 mcg single use |
8 (11) msec |
| 180 mcg + 2 additional doses of 90 mcg 2 hours apart (total 3 doses) |
11 (14) msec |
Pharmacokinetics
Dexmedetomidine exposure (Cmax and AUC) increased in a dose proportional manner in the dose range of 20 mcg (0.17 times the lowest recommended initial dose of 120 mcg) to 180 mcg after single sublingual administration of IGALMI.
The mean time for film to dissolve in the mouth was about 6 to 8 minutes and 18 minutes following sublingual and buccal administration, respectively. Dexmedetomidine was quantifiable in plasma generally after 5 to 20 minutes post dosing.
Absorption
The absolute bioavailability of dexmedetomidine was about 72% and 82% following sublingual and buccal administration of IGALMI, respectively. When water was taken at two hours post dose, comparable exposures of dexmedetomidine were observed when IGALMI was administered by both routes.
Mean maximal plasma concentrations of dexmedetomidine were reached approximately two hours after sublingual or buccal administration of IGALMI. Following sublingual administration of 40 mcg of IGALMI (0.33 times the lowest recommended initial dose) with water drinking at two hours post dose and 20 mcg dexmedetomidine intravenous infusion for 90 minutes in healthy volunteers:
- The mean peak plasma concentration (Cmax) of dexmedetomidine was 143 ng/L and 144 ng/L, respectively.
- The mean area under concentration curve (AUC) of dexmedetomidine was 851 hour*ng/L and 584 hour*ng/L, respectively.
Effect Of Drinking Water On Absorption
Compared to drinking water at two hours post sublingual administration of IGALMI, early water intake (as early as 15 minutes post dose) had minimal effects on the rate or extent of absorption of dexmedetomidine.
Effects of early water intake (i.e., before two hours post dose) on the absorption of dexmedetomidine has not been evaluated following buccal administration.
Distribution
The steady-state volume of distribution (Vss) of dexmedetomidine following intravenous administration was approximately 118 liters. Dexmedetomidine protein binding was assessed in the plasma of healthy male and female subjects. The average protein binding was 94% and was constant across the different plasma concentrations tested. Protein binding was similar in males and females. The fraction of dexmedetomidine that was bound to plasma proteins was significantly decreased in subjects with hepatic impairment compared to healthy subjects.
The potential for protein binding displacement of dexmedetomidine by fentanyl, ketorolac, theophylline, digoxin and lidocaine was explored in vitro, and negligible changes in the plasma protein binding of dexmedetomidine IV were observed. The potential for protein binding displacement of phenytoin, warfarin, ibuprofen, propranolol, theophylline and digoxin by dexmedetomidine hydrochloride injection was explored in vitro and none of these compounds appeared to be significantly displaced by intravenous dexmedetomidine.
Elimination
Metabolism
Dexmedetomidine undergoes almost complete biotransformation with very little unchanged dexmedetomidine excreted in urine and feces. Biotransformation involves both direct glucuronidation as well as cytochrome P450 mediated metabolism. The major metabolic pathways of dexmedetomidine are: direct N-glucuronidation to inactive metabolites; aliphatic hydroxylation (mediated primarily by CYP2A6 with a minor role of CYP1A2, CYP2E1, CYP2D6 and CYP2C19) of dexmedetomidine to generate 3-hydroxy-dexmedetomidine, the glucuronide of 3-hydroxy-dexmedetomidine, and 3- carboxy-dexmedetomidine; and N-methylation of dexmedetomidine to generate 3-hydroxy Nmethyl- dexmedetomidine, 3-carboxy N-methyl-dexmedetomidine, and dexmedetomidine-N-methyl O-glucuronide.
Excretion
The mean terminal elimination half-life (t½) of dexmedetomidine is approximately 2.8 hours following sublingual or buccal administration of IGALMI. Clearance is estimated to be approximately 39 L/h following intravenous administration.
A mass balance study demonstrated that after nine days, an average of 95% of the radioactivity, following intravenous administration of radiolabeled dexmedetomidine, was recovered in the urine and 4% in the feces. No unchanged dexmedetomidine was detected in the urine. Approximately 85% of the radioactivity recovered in the urine was excreted within 24 hours after the infusion. Fractionation of the radioactivity excreted in urine demonstrated that products of N-glucuronidation accounted for approximately 34% of the cumulative urinary excretion. In addition, aliphatic hydroxylation of parent drug to form 3-hydroxy-dexmedetomidine, the glucuronide of 3-hydroxy-dexmedetomidine, and 3-carboxylic acid-dexmedetomidine together represented approximately 14% of the dose in urine. N-methylation of dexmedetomidine to form 3-hydroxy N-methyl dexmedetomidine, 3-carboxy Nmethyl dexmedetomidine, and N-methyl O-glucuronide dexmedetomidine accounted for approximately 18% of the dose in urine. The N-methyl metabolite itself was a minor circulating component and was undetected in urine. Approximately 28% of the urinary metabolites have not been identified.
Specific Populations
Male And Female Patients
There was no observed difference in the pharmacokinetics of intravenous dexmedetomidine due to sex.
Geriatric Patients
The pharmacokinetic profile of intravenous dexmedetomidine was not altered by age. There were no differences in the pharmacokinetics of intravenous dexmedetomidine in young (18–40 years), middle age (41–65 years), and geriatric (>65 years) subjects.
Patients With Hepatic Impairment
In subjects with varying degrees of hepatic impairment (Child-Pugh Class A, B, or C), clearance values for intravenous dexmedetomidine were lower than in subjects with normal hepatic function [see DOSAGE AND ADMINISTRATION]. After an intravenous infusion of 0.6 mcg/kg of this dexmedetomidine product over 10 minutes the mean clearance values for subjects with mild, moderate, and severe hepatic impairment were 74%, 64% and 53% of those observed in subjects with normal hepatic function, respectively. Mean clearances for free drug were 59%, 51% and 32% of those observed in subjects with normal hepatic function, respectively.
Patients With Renal Impairment
Dexmedetomidine pharmacokinetics (Cmax, Tmax, AUC, t½, CL, and V) were not significantly different in patients with creatinine clearance <30 mL/minute compared to subjects with normal renal function.
Drug Interactions Studies
In vitro studies in human liver microsomes demonstrated no evidence of cytochrome P450 mediated drug interactions that are likely to be of clinical relevance.
Animal Toxicology And/Or Pharmacology
Twice daily sublingual administration of 120 to 320 mcg/day of dexmedetomidine to dogs for 28 days caused decreased heart rate and moderate sedation up to 3.5 hours post dose. A single male dog (out of 32 treated dogs) dosed 320 mcg/day (equivalent to the MRHD of 360 mcg/day) exhibited inflammation, necrosis, myofiber degeneration, and hemorrhage at the sublingual treatment site. No adverse effects were noted at 240 mcg/day (less than the MRHD of 360 mcg/day).
Clinical Studies
The effectiveness of IGALMI for the acute treatment of agitation associated with schizophrenia or bipolar I or II disorder in adults was established in two randomized, double-blind, placebo-controlled, fixed-dose studies (Studies 1 and 2):
- Study 1 (NCT04268303) included 380 patients who met DSM-5 criteria for schizophrenia, schizoaffective or schizophreniform disorder. The population was 18 to 71 years of age (mean age was 46 years old); 37% female and 63% male; 78% Black, 20% White, 1% multiracial, and 1% Asian.
- Study 2 (NCT04276883) included 378 patients who met DSM-5 criteria for bipolar I or II disorder. The population was 18 to 70 years of age (mean age was 47 years old); 55% female and 45% male; 56% Black, 41% White, 1% Asian, 1% multiracial, and 1% other.
The Positive and Negative Syndrome Scale-Excited Component (PEC) is an investigator-rated instrument consisting of 5 items: poor impulse control, tension, hostility, uncooperativeness, and excitement. Each item is scored on a scale from 1 to 7 (1=absent, 2=minimal, 3=mild, 4=moderate, 5=moderate-severe, 6=severe, 7=extremely severe). The total PEC score ranges from 5 to 35, with higher scores reflecting greater overall symptom severity. For enrollment in the studies, patients had to be judged to be clinically agitated with a total PEC score of ≥ 14, with at least one individual item score ≥ 4. In both studies, patients were admitted to a clinical research unit or a hospital and remained under medical supervision for at least 24 hours following treatment.
Patients were randomized to receive a single sublingual dose of 180 mcg of IGALMI, 120 mcg of IGALMI, or placebo. The primary efficacy endpoint in both studies was the change from baseline in the PEC score, assessed two hours following the initial dose. The key secondary endpoint was the time to effect onset, assessed by measuring the change from baseline in PEC score at 10, 20, 30, 45, 60, and 90 minutes after the initial dose administration.
In both studies, mean baseline PEC scores were similar in all treatment groups (Table 5). The mean change from baseline in the PEC total score at two hours after the first dose in patients treated with 180 mcg and 120 mcg of IGALMI was statistically greater than patients who received placebo (Table 5).
Examination of population subsets (race and sex) on the primary endpoint did not show evidence for differential responsiveness between White and Black or female and male patients. The clinical studies did not include enough patients of other races or patients ≥65 years of age to determine whether there were differences in effectiveness for those groups.
Table 5: Primary Efficacy Results for Change from Baseline in the PEC Score at Two Hours in Agitated Patients with Schizophrenia or Bipolar I or II Disorder (Studies 1 and 2)
| Study |
Treatment Group |
Number of Patients |
Mean Baseline PEC Score (SD) |
LS Mean Change from Baseline to 2 hour Post First Dose (SE) |
LS Mean Difference (95% CI) |
| Study 1 |
IGALMI 180 mcg* |
125 |
17.6 (2.7) |
-10.3 (0.4) |
-5.5
(-6.5, -4.4) |
| IGALMI 120 mcg* |
129 |
17.5 (2.5) |
-8.5 (0.4) |
-3.7
(-4.8, -2.7) |
| Placebo |
126 |
17.6 (2.3) |
-4.8 (0.4) |
- |
| Study 2 |
IGALMI 180 mcg* |
126 |
18.0 (3.0) |
-10.4 (0.4) |
-5.4
(-6.5, -4.3) |
| IGALMI 120 mcg* |
126 |
18.0 (2.7) |
-9.1 (0.4) |
-4.1
(-5.1, -3.0) |
| Placebo |
126 |
17.9 (2.9) |
-5.0 (0.4) |
- |
SD=standard deviation; SE=standard error; LS Mean=least-squares mean; CI=unadjusted confidence interval; PEC=Positive and Negative Syndrome Scale-Excited Component
*IGALMI doses that were statistically significantly superior to placebo after adjusting for multiplicity. |
Figures 1 and 2 show the changes from baseline in PEC score at each time point assessed up to two hours following the initial dose. In Study 1, the decrease in agitation with IGALMI, compared to placebo, was statistically significant beginning at 20 minutes following dosing with the 180 mcg dose and 30 minutes after the 120 mcg dose. In Study 2, the decrease in agitation with IGALMI, compared to placebo, was statistically significant beginning at 20 minutes after treatment with both 120 mcg and 180 mcg doses.
Figure 1: Mean Change from Baseline in PEC Score Through Two Hours after a Single Dose in Agitated Patients with Schizophrenia (Study 1)
Figure 2: Mean Change from Baseline in PEC Score Through Two Hours after a Single Dose in Agitated Patients with Bipolar I or II Disorder (Study 2)