Emergency-Use Injectable Combination Products: FDA Approvals and Supporting Evidence

FDA-approved emergency-use injectable combination products: approvals and the evidence behind them

Epinephrine, naloxone, and glucagon share a regulatory problem: they treat conditions (anaphylaxis, opioid overdose, severe hypoglycemia) where the patient cannot self-administer a conventional injection and where a placebo-controlled efficacy trial in the actual emergency would be unethical or infeasible. Over the past decade and a half FDA has approved a series of drug-device combination products, autoinjectors and ready-to-use prefilled syringes, that put these drugs into the hands of laypersons. The active ingredients are old and well characterized; the review burden shifts to the device and to human factors. This overview walks through the injectable products FDA has cleared, the approval pathway each used, and the specific evidence that supported them.

How FDA evaluates an emergency injectable combination product

For all three drug classes the active moiety is a legacy molecule with established efficacy, so most of these products were filed under the 505(b)(2) pathway, relying on FDA's prior findings for a reference product and bridging to it. The bridge is almost always pharmacokinetic rather than clinical: a comparative bioavailability or bioequivalence study in healthy volunteers, with FDA emphasizing early-exposure parameters (Cmax, Tmax) because onset speed is what matters in a rescue setting ^83139204. Because a deliberate anaphylaxis or overdose reversal trial is not ethical, FDA has repeatedly accepted PK matching in lieu of a clinical endpoint study ^83139148.

That leaves the device and its usability as the real review questions. Human-factors (HF) validation, whether an untrained caregiver or child can execute every critical use step under simulated stress, is central to these approvals, and it has been the deciding factor in complete-response actions (Symjepi) and postmarketing requirements (Zimhi) ¹⁶²¹⁹⁶. Glucagon is the partial exception: the dasiglucagon product Zegalogue was filed as a new molecular entity and carried full Phase 3 efficacy trials, and Gvoke's ready-to-use glucagon included a comparative glucose-response study.

Epinephrine devices for anaphylaxis

Auvi-Q (epinephrine autoinjector), Kaleo, 2012

Auvi-Q (NDA 201739) was approved on August 10, 2012 under a 505(b)(2) NDA relying on the established safety and effectiveness of the reference product EpiPen/EpiPen Jr ⁵⁵⁸⁰. It is a compact autoinjector with a retractable needle and electronic audible/visual voice instructions, self-contained with no assembly or priming ⁷⁹⁸⁰⁷⁴.

There was no efficacy trial in patients experiencing anaphylaxis. The single pivotal study, INT0802, was a bioavailability study, not an efficacy study: a randomized, single-blind, active-controlled, three-period crossover comparison of the autoinjector versus EpiPen 0.3 mg in roughly 69 to 71 healthy adults under fasting conditions ⁷⁴⁸⁸⁸⁶. PK endpoints included Cmax, Tmax, AUC and terminal half-life, analyzed with a reference-scaling average bioequivalence approach appropriate for a highly variable drug ⁸⁴⁸⁹. FDA concluded the product was bioequivalent to EpiPen, with largely overlapping concentration-time curves ⁸⁰⁸⁶. A single 0.3-mg bioequivalence trial was accepted to support both the 0.3-mg and pediatric 0.15-mg strengths ⁷⁵.

Three simulated-use human-factors studies (INT0801, INT0803, INT-FE-0901) carried the usability case, none administering active drug ⁷²⁸⁸. INT0801 (48 lay users, ages 7 to 55) showed fewer use errors than comparator devices and drove design changes to the safety guard, voice prompts and labeling ⁶⁹⁹¹⁸². INT0803 (28 healthcare workers, 505 test injections) validated the retractable needle with no retraction failures ⁷⁷. The final validation study INT-FE-0901 (40 adult and pediatric participants) reported 100% successful simulated injection on the redesigned device, and FDA found no outstanding human-factors deficiencies ⁷⁰⁷¹⁷².

Symjepi (epinephrine prefilled syringe), Adamis, 2017

Symjepi (NDA 207534) was approved June 15, 2017, also under 505(b)(2) referencing EpiPen, but as a manually injected single-dose prefilled syringe rather than an autoinjector ^25160173. There were no new clinical efficacy trials; FDA relied on the established first-line role of epinephrine in anaphylaxis ¹⁵⁷¹⁷⁴. Notably, FDA granted a biowaiver for both IM and SC administration, so no human PK or bioequivalence studies were conducted, based on formulation and route similarity to the listed drug ¹⁵⁷¹⁷⁴.

The review hinged on the device. The original submission was not approvable because FDA found it could not reliably deliver the labeled 0.3 mL/0.3 mg dose, requiring redesign ^156159171. The final device achieved a mean delivered volume of 0.297 mL and passed dose-accuracy, needle-guard, drop, vibration, aging and injection-through-clothing testing ^165170169. Human factors nearly sank the program: an earlier study on the redesigned device showed critical use failures (failure to remove the needle cap or premature needle-guard deployment in about 4% of participants, premature plunger depression in about 3%), triggering FDA's second Complete Response in June 2016 ¹⁶². After further device and labeling modifications and new HF data submitted in December 2016, FDA concluded the concerns were resolved ¹⁶⁰¹⁷³.

Context: nasal and legacy alternatives

The original EpiPen (NDA 019430) dates to the 1980s and predates the modern combination-product framework ²⁰. More recently FDA approved neffy (NDA 214697), an epinephrine nasal spray, on August 9, 2024, as a needle-free alternative for the same indication ⁶⁴. These products define the reference and competitive landscape but sit outside the injectable-device scope of this overview.

Naloxone injectable devices for opioid overdose

Evzio (naloxone autoinjector), Kaleo, 2014

Evzio (NDA 205787) was approved April 3, 2014 under 505(b)(2), relying on FDA's prior finding for Narcan injection (NDA 016636) and using a generic naloxone prefilled syringe as the PK reference because Narcan had been discontinued ⁶⁷¹³⁴. It was the first naloxone autoinjector designed for community use by laypersons, with automatic needle insertion and retraction and electronic voice prompts ¹³³¹³⁵. Kaleo later obtained a separate NDA (209862) for a higher-concentration autoinjector configuration in October 2016 ⁶⁸.

FDA determined a clinical overdose-reversal trial was neither ethical nor feasible, so approval rested on a single comparative relative-bioavailability study in healthy volunteers, with Cmax and Tmax as the PK targets; FDA's review concluded the study demonstrated bioequivalence to the generic naloxone comparator ¹³⁹¹⁴⁸. The human-factors package included six formative studies and a summative validation in 40 untrained participants (19 juveniles, 21 adults); 36 of 40 delivered an effective simulated dose, with the four failures attributed to insufficient activation pressure, not holding for the required interval, or using the trainer ¹³¹¹⁵¹. FDA found the HF validation acceptable but required a postmarketing study on needle length safety in infants under one year, where the needle could strike bone ¹⁴³.

Zimhi (high-dose naloxone injection), ZMI Pharma/Adamis, 2021

Zimhi (NDA 212854) was approved October 15, 2021 under 505(b)(2), a Type 5 (new formulation) filing bridging to Narcan injection ²¹¹⁹⁰. It is a single-use prefilled syringe delivering a high 5 mg/0.5 mL dose IM or SC, intended for users age 12 and older ²⁰². The pivotal evidence was the comparative PK study APC 6000-03: a single 5-mg IM dose versus 2-mg IM naloxone ²⁰⁴. Zimhi matched the comparator's 15-minute median Tmax while producing roughly 4.9-fold higher Cmax and 2.7 to 2.8-fold higher AUC, exceeding FDA's benchmark that community-use naloxone should meet or exceed 0.4 mg IM naloxone ^204185192. There were no clinical efficacy trials in overdose patients, and any advantage of the higher dose against high-potency synthetic opioids was considered theoretical ¹⁸⁸²⁰⁰.

The device raised the most concern. Zimhi uses a manually deployed needle safety guard, and FDA found inadequate data that untrained laypersons could deploy it reliably, leaving a needlestick risk until deployment ¹⁹³¹⁹⁴. Single-device delivery reliability was reported at 99.96%, below FDA's requested 99.99% threshold, and FDA declined to accept the two-device carton as compensation because a patient might need both doses ¹⁹⁷. FDA recommended postmarketing requirements including redesign to an automatically deploying needle guard and a fault-tree analysis demonstrating 99.999% reliability ¹⁹⁶.

Context: nasal naloxone

The dominant naloxone products remain nasal sprays: Narcan nasal spray (NDA 208411, approved November 18, 2015, later moved to over-the-counter status) and Kloxxado (NDA 212045, April 29, 2021) ³⁴⁶⁶. These are not injectable combination products but are the primary alternatives clinicians and RA professionals will compare against Evzio and Zimhi.

Glucagon rescue injectables for severe hypoglycemia

Gvoke (ready-to-use liquid glucagon), Xeris, 2019

Gvoke (NDA 212097) was approved September 10, 2019 as a ready-to-use, non-aqueous liquid glucagon in two configurations sharing one formulation: the Gvoke HypoPen autoinjector and a manual prefilled syringe ⁴⁴¹²⁹. Its clinical rationale was eliminating the nine-step reconstitution required by legacy lyophilized glucagon kits ¹²⁹. The program was developed under 505(b)(2) intent relying on prior glucagon products; the record characterizes the NDA as Type 3 (new dosage form), standard review ¹²⁹¹²⁵.

The pivotal adult study XSGP-303 was a randomized, single-blind, two-period crossover in 81 adults with type 1 diabetes, comparing 1-mg subcutaneous G-Pen by autoinjector against Lilly Glucagon, assessing plasma-glucose recovery from induced hypoglycemia below 50 mg/dL ¹²⁴. FDA noted the glucose response was 3 to 4 minutes slower than reconstituted Lilly glucagon, but accepted that far faster preparation (under 30 seconds versus over 90 seconds for the reconstituted comparator) could offset this in real use ¹²¹. A PK/PD study, XSGP-101, bridged the autoinjector and prefilled-syringe presentations, meeting the 80% to 125% bioequivalence criterion between configurations ¹²⁴. Summative human-factors validation was performed for both presentations (XSGP-HF-3 and XSGP-HF-5, 75 participants each spanning first responders and caregivers) ¹²⁴. FDA did not find demonstrated morbidity or mortality benefit over existing treatment, which is why Fast Track was denied and review was standard ¹²⁵.

Zegalogue (dasiglucagon autoinjector), Zealand Pharma, 2021

Zegalogue (NDA 214231) was approved March 22, 2021 and is the outlier in this group ⁵⁹. Dasiglucagon is a soluble glucagon analog and a new molecular entity; because FDA found insufficient justification to rely on prior GlucaGen findings, it was filed under the full 505(b)(1) pathway with genuine efficacy trials ⁹⁷¹¹⁸. It is a ready-to-use aqueous 0.6-mg subcutaneous injection available as an autoinjector and prefilled syringe for patients aged 6 and older.

Approval rested on three randomized, double-blind, placebo-controlled Phase 3 hypoglycemic-clamp trials: Study 16137 (168 adults), Study 17145 (44 adults, autoinjector), and pediatric Study 17086 (41 patients aged 6 to under 18) ¹⁰⁸. The primary endpoint was time to plasma-glucose recovery, defined as the first increase of at least 20 mg/dL from baseline without IV rescue glucose ¹¹¹¹¹⁷. Dasiglucagon achieved a median recovery of 10 minutes across all three trials versus 30 to 40 minutes for placebo, with all log-rank p-values below 0.001 and a recovery-time ratio of 0.29 ¹⁰⁵¹¹¹. GlucaGen active-reference arms showed descriptively similar recovery (10 to 12 minutes), though the trials were not powered for formal comparison ⁹⁹¹⁰⁰. A storage-bridging study (17084) confirmed clinical performance under dual refrigerated/room-temperature storage, with only about a 24-second difference in recovery time ¹¹⁹. DMEPA human-factors review of both presentations identified use errors (incorrect injection site, injection through clothing, early device removal) but judged the residual risks acceptable with labeling and Instructions for Use ¹¹²¹¹⁶.

Context: nasal glucagon

Baqsimi, a nasal powder glucagon (NDA 210134), was approved July 24, 2019 and is the needle-free alternative in this class ⁴⁸. As with the other classes, the nasal option is the main comparator but not itself an injectable combination product.

Cross-cutting evidentiary themes

Several patterns recur across these approvals. First, PK bridging substitutes for clinical efficacy in every product except the dasiglucagon NME, and FDA consistently prioritizes onset parameters over total exposure because rescue speed is the clinical objective ^83139204. Second, human factors is where these applications succeed or fail: Auvi-Q's usability data was affirmatively strong, Symjepi cleared only after two Complete Response actions tied to use errors, and Zimhi carried unresolved needle-guard and reliability concerns into postmarketing requirements ^82162196. Third, the practical benefit these devices claim, eliminating reconstitution or enabling untrained community use, is often accepted by FDA as a reasonable offset to modest pharmacodynamic tradeoffs (Gvoke's slower glucose response, Zimhi's manual guard), even where a formal morbidity or mortality benefit was not demonstrated ¹²¹¹²⁵. Finally, in each therapeutic area a needle-free nasal alternative (neffy, Narcan/Kloxxado, Baqsimi) now competes with the injectable devices, reshaping the reference landscape RA teams should track when planning new filings.