Diazepam nasal spray contains dodecyl maltoside (Intravail
®; Neurelis, Inc. [San Diego, CA, USA]), an alkylsaccharide excipient that facilitates diazepam absorption across the nasal mucosa [
25,
53]. Dodecyl maltoside transiently increases nasal epithelial permeability by relaxing tight intercellular junctions [
25]. In a study with sumatriptan, dodecyl maltoside has been shown to increase bioavailability while decreasing time to
Cmax [
53]. Vitamin E is used to solubilize diazepam for delivery in an aqueous spray [
25]. Diazepam nasal spray is stable at room temperature, with a shelf life longer than 2 years [
54]. Diazepam nasal spray comes in 5-, 10-, 15-, and 20-mg doses (15- and 20-mg doses require two sprayers of 7.5 or 10 mg each: one for each nostril), and dose is based on patient age and weight (0.3 mg/kg for patients aged 6–11 years; 0.2 mg/kg for patients aged 12 years or older) [
39]. Each blister pack contains one full dose, and there are two blister packs (doses) per carton [
39]. Administration involves proper handling of the sprayer and positioning of the nozzle in the nostril (Table
1) [
55]. If needed, a second dose may be given at least 4 h after the first dose, using the second blister pack [
29].
Clinical Development of Diazepam Nasal Spray
Diazepam nasal spray was approved by the FDA through the 505(b)(2) regulatory pathway, which utilizes a reference drug (diazepam rectal gel) for support of safety and effectiveness [
56]. In one of the trials for diazepam rectal gel, two or three doses of diazepam rectal gel (based on age) were administered, with the second dose 4 h after the first dose and, for adults, another at 12 h in order to maintain plasma levels of diazepam (150–300 ng/mL) [
24], which contributed to the FDA label requirements of 4 h between first and second doses of diazepam nasal spray [
57]. As part of the 505(b)(2) pathway, diazepam nasal spray inherited the same labeling for use as the rectal gel [
56]. In the summary of findings, the FDA stated that the intranasal administration route of diazepam nasal spray was clinically superior because it “provides a major contribution to patient care over the rectal route of administration by providing a significantly improved ease of use” [
58].
The pharmacokinetics of diazepam nasal spray was investigated in phase 1 studies conducted in healthy volunteers [
43,
59,
60] and patients with epilepsy [
61]. An open-label, three-way crossover study compared the bioavailability and other pharmacokinetic variables of two intranasal formulations of diazepam (nasal solution [the formulation for diazepam nasal spray] and nasal suspension) with IV formulation of diazepam [
59]. Bioavailability of diazepam nasal spray (10 mg) was 97%, whereas that of the nasal suspension (10 mg) was 67%.
Cmax of diazepam nasal spray and the nasal suspension were 272 and 221 ng/mL, respectively [
59], which were in a therapeutic range associated with reductions in electroencephalogram spike counts [
62]. The half-life of diazepam was similar for both intranasal formulations (diazepam nasal spray, 49.2 h; nasal suspension, 56.2 h) and the IV formulation (56.2 h) [
59], suggesting that diazepam was effectively absorbed using the intranasal route.
An open-label, randomized crossover study assessed the dose proportionality and pharmacokinetics of diazepam nasal spray [
60]. Diazepam nasal spray administered in 5-, 10-, and 20-mg doses achieved mean
Cmax of 85.6, 133.6, and 235.3 ng/mL, respectively, which was suggestive of dose proportionality, although a formal analysis of dose proportionality was inconclusive owing to intersubject variability [
60]. An open-label, randomized, single-dose, three-treatment, three-period, six-sequence crossover study compared bioavailability and safety of diazepam nasal spray with orally and rectally administered diazepam [
43]. Pharmacokinetic variability (%GCV) of diazepam was 2- to 4-fold lower with nasal spray (44–81%) than rectal gel (83–170%), with rectal gel administered under ideal conditions (i.e., a fasted state, with enemas administered the night before testing and 1 h before testing) [
43]. A single-dose pharmacokinetics and safety study of diazepam nasal spray conducted in patients with epilepsy [
61] reported comparable pharmacokinetic characteristics during ictal/peri-ictal and interictal periods, which were similar to those previously described in healthy volunteers [
60,
61].
Diazepam Nasal Spray: Safety and Effectiveness Profile
The safety of diazepam nasal spray in patients with epilepsy was investigated in phase 1 and phase 3 clinical trials [
61,
63]. Exploratory outcomes related to effectiveness and patient experiences were assessed in the phase 3 study [
63]. There were no discontinuations, serious TEAEs, or deaths considered related to treatment in the clinical development program, which included 220 patients with epilepsy across studies [
61,
63].
A phase 3, long-term, repeat-dose, open-label safety study of diazepam nasal spray (NCT02721069) was performed in 163 patients with epilepsy who received at least one dose of diazepam nasal spray [
63]. A total of 82% of patients experienced TEAEs, 31% experienced serious adverse effects, and 18% experienced treatment-related TEAEs. Nasal discomfort was the most common treatment-related TEAE (6%), followed by headache (2%), dysgeusia (2%), epistaxis (2%), and somnolence (2%). There were no changes of clinical relevance in respiratory rate, laboratory tests, or vital signs with treatment [
63]. In patients aged 6–11 years, rates of TEAEs, serious TEAEs, and treatment-related TEAEs were 91%, 40%, and 7%, respectively [
64].
Administration of diazepam nasal spray was easily accomplished and rapidly effective. For example, the median time from seizure onset to administration was 2 min (range 1–750 min), whereas the median time from administration to seizure cessation was 4 min (range 1–1151 min) [
65]. Consistency of effectiveness of diazepam nasal spray was shown by the low rate of a second dose used to treat seizure clusters (13%) over a 24-h period [
63]. Seventy-nine patients (48%) received a second dose [
66], and eight patients accounted for 50% of those who received a second dose (data on file). The safety and effectiveness of diazepam nasal spray were similar for the overall population and among patients who received concomitant benzodiazepines [
63], pediatric patients with developmental and epileptic encephalopathies [
67], and patients who averaged more than 2 to 5 doses per month [
63].
Patient and Caregiver Perspectives on Diazepam Nasal Spray
In an exit survey from the phase 3 open-label safety study of diazepam nasal spray, 59% of patients indicated that they were back to baseline within an hour of administration, and 59% of caregivers were able to return to daily activities within an hour of administration [
68]. Eighty-nine percent of patients said that it was extremely easy or very easy to train others on administration of diazepam nasal spray, and 79% were comfortable doing activities outside the home with diazepam nasal spray available [
68]. In patients who self-administered diazepam nasal spray, 78% described administration as either very easy or extremely easy, and 67% were somewhat, very, or extremely comfortable administering in a public setting. In the caregiver survey, 100% responded that it was extremely easy or very easy to be trained to administer diazepam nasal spray, and 90% were extremely or very comfortable administering diazepam nasal spray in public [
68].
Quality of Life
Adult patient quality of life was assessed in the phase 3 open-label safety study of diazepam nasal spray using the Quality of Life in Epilepsy (QOLIE)-31-P instrument [
69]. Overall scores using the QOLIE-31-P instrument to address quality of life in this patient sample with drug-resistant epilepsy were stable over time. Importantly, scores involving subscales of Seizure Worry and Social Functioning, which were hypothesized to be most relevant to use of rescue treatment, showed clinically meaningful improvements over the course of the study, indirectly suggesting a potential reduction in the burden of seizure clusters [
69]. The peace of mind of having diazepam nasal spray on-hand also might contribute to these improvements in QOLIE-31-P subscale scores.
Exploring Long-Term Change in Interval Between Seizure Clusters
Conventional outcomes used to determine the effectiveness of treatment for seizure clusters typically include measures of frequency and recurrence [
70]. Patterns of seizure clusters with long-term use of intermittent acute seizure rescue treatments are not well characterized. A post hoc analysis of data from the phase 3 open-label safety study of diazepam nasal spray examined the interval between treated seizure clusters (SEIVAL) over time in patients that received intermittent treatment with diazepam nasal spray. In patients with intervals between clusters in each of four 90-day periods, the mean interval between usage of diazepam nasal spray (excluding re-treatments for a single cluster) increased from 14 days during the initial period (days 1–90) to 27 days by the final period (days 271–360;
P ≤ 0.001 compared with period 1). A conservative analysis that included second doses for a seizure cluster resulted in a similar increase in intervals, from 12 days in the first 90 days to 26 days in the last 90 days (
P ≤ 0.001). Changes in concomitant ASMs (drug or dose) did not explain the changes over time [
70]. Exploration of the cause for this pattern of increased duration between seizure clusters over time with intermittent therapy has allowed for hypothesis generation that was previously published [
70].