Autoinjector Use Errors vs. Device Defects: A Comprehensive FDA Evidence Review

Report Date: April 17, 2026
Sources: FDA MAUDE, FDA Drugs@FDA (DMEPA/combination product reviews), FDA 510(k) database, FDA Guidance Documents, FDA Warning Letters

Methodology

This report was compiled by querying multiple FDA databases in parallel using lexical search strategies specifically designed to surface use-error-coded adverse events, which are frequently masked in MAUDE under event types of "Malfunction" or "Injury" rather than an explicit "use error" category. MAUDE was searched using at least 10 different keyword clusters targeting distinct use-error modes (needle stick, premature activation, cap failure, incomplete dose, failure to activate, wrong technique, device reuse, activation force, and explicit user-error language), supplemented by product-code–level searches (KZH for autoinjectors, FMI for pen needles) and brand-specific searches (EpiPen, HUMIRA, Whisperject). FDA guidance databases were searched for human factors, use-related risk analysis, and IFU/labeling guidance for combination products. Drug review documents were searched for DMEPA (Division of Medication Error Prevention and Analysis) findings on autoinjector combination products. 510(k) submissions were searched for human factors validation data. The fundamental challenge noted throughout: MAUDE does not have a discrete "use error" event-type code—use errors are submitted as Malfunction, Injury, or Other depending on the reporter's framing, making systematic counting inherently underestimative.

1. Background: Why Use Errors Are Hard to Detect in MAUDE

FDA's MAUDE database captures Medical Device Reports (MDRs) classified by event type (Injury, Malfunction, Death, Other). There is no discrete "use error" event type. When a patient misuses an autoinjector, the report is typically coded as:

Malfunction — if the device "failed" from the reporter's perspective (even if caused by mishandling)
Injury — if a physical harm occurred (needlestick, tissue injury)
Other — catch-all

FDA guidance formally defines a use error as "a user action or lack of action that is different from what the manufacturer expected, is not solely caused by device failure, and that produced an unexpected result" ³²³. Crucially, device malfunction and use error are not mutually exclusive—a device may malfunction because of a use error (e.g., needle breakage from incorrect installation angle). This ambiguity pervades the MAUDE record corpus.

In the searched MAUDE records for autoinjectors (device_generic_name = "autoinjector" and product code KZH), the event type breakdown in the database segment accessible was:

Injury events: 10 records ³⁴–⁴³
Malfunction events: 29 records ⁶⁵–⁹³
Death events: 0 records

These figures reflect only records coded specifically with the generic name "autoinjector"—a major undercount, since many autoinjector combination products are filed under the brand name (e.g., "EPIPEN 0.3 MG AUTOINJECTOR," "WHISPERJECT AUTOINJECTOR"), pen-needle records are coded separately under product code FMI, and combination product drug-device pairs may be reported to FAERS (not MAUDE) when the drug is seen as primary.

2. MAUDE Evidence by Use-Error Category

2.1 Needlestick / Accidental Needle Injury

MAUDE findings: Multiple reports documented needle-related injuries attributable to use errors.

Device	Mechanism	Outcome	Source
BD Nano Ultra-Fine Pen Needle	Needle broken off into patient's stomach/abdomen	ER visit, X-ray; doctor advised monitoring	⁵¹
BD Ultra-Fine Pen Needle	Needle broke off in left abdomen	X-ray, ultrasound, probing, antibiotics prescribed	⁵⁹
BD Autoshield Duo Safety Pen Needle	Needle broke off into syringe → clean needlestick	Manufacturer could not confirm defect	⁴⁵
BD Nano Ultra-Fine Pen Needles, 32G×4mm	Unused pen needle caused roommate needlestick in left palm	Blood tests for HIV and hepatitis C ordered	⁴⁹
EpiPen Jr	Grey cap pulled with needle pointing away from body → needle ejected from black cap	Accidental needlestick	¹⁰⁰
EpiPen	Device stuck in patient's leg; needle bent with burr at tip on removal	Pain, bruising; difficult extraction	⁵⁵
EpiPen Jr	Needle would not release from skin; hook at needle end required scalpel nick to release	Minor surgical intervention	¹⁰⁴
EpiPen	Needle bent in leg muscle, very difficult to withdraw	Pain, bruising	¹⁰⁷

Use-error attribution: Manufacturer investigation for BD pen needle breakage events explicitly cited user error as root cause: "the possible root cause for this issue (bent non-patient end cannula) is: user error" — specifically, installing the pen needle at an angle rather than straight-on to the pen device. Insufficient patient training was specifically flagged as a contributing factor ⁴⁶⁵²⁵³.

Key mechanism: Misaligned needle installation (at an angle) causes the rear cannula to kink or break. This results in both delivery failure and potential embedded needle fragments.

2.2 Incomplete Dose / Partial Dose Delivery

This is the single most common use-error mode in the searched records, appearing across multiple device platforms and frequently coded as "Malfunction" even when user technique is the root cause.

Device	Failure Description	User Error Component	Source
HUMIRA pen	Patient heard no click, pulled pen away — dose released onto floor	Removed device before injection completed	²⁷³
HUMIRA pen	Needle did not penetrate skin; indicator didn't move; liquid on floor	Likely improper positioning/pressure	²⁷⁴
HUMIRA pen	Patient did not feel needle prick or liquid entering; thought dose not delivered	May have removed prematurely	²⁷⁷
HUMIRA pen	Needle came partway down but not fully; medication leaked out on removal	Insufficient pressure or wrong angle	²⁸³
HUMIRA pen	Medication squirted on patient; dose missed	Unintended release on removal	²⁷⁵
Autoject II for Glass Syringe	Only partial dose of Copaxone received	Reported as "error with the autoinjector device"	¹¹⁴
Autoject	Device did not inject when button pressed; patient may have missed 2 doses	Device-user interaction failure	¹¹⁵
Whisperject	Device loaded but nothing came out; reporter noted patient "more than likely" using incorrectly	Incorrect use suspected	²⁹¹
Whisperject	Plunger very difficult to push; medication leaked out	User force/technique issue	²⁹⁷
Omnitrope Pen	Child does not get full dose when injecting	Caregiver technique issue	²⁵⁵

DMEPA data (epinephrine autoinjector): In an FDA DMEPA-reviewed human factors validation study for an epinephrine autoinjector, failure to depress the plunger fully was a documented critical task failure. DMEPA specifically attributed this to negative transfer from EpiPen use, where participants muscle-memoried the EpiPen activation sequence (press and hold) rather than pressing a plunger ⁴¹⁰⁴¹¹. The study also found 3 instances of failure to remove the needle cap before attempting injection — 2 naive trained lay users in the first injection, 1 trained patient in the second injection ⁴¹¹.

2.3 Premature / Accidental Activation

MAUDE findings — highest-severity use-error category in the record set:

Device	Mechanism	Outcome	Source
Whisperject Autoinjector	Device "misfired" — injected too forcefully and too quickly into abdomen	Bleeding, bruising, blood blister, skin necrosis, staph infection, wound requiring debridement, antibiotics	¹¹¹
Whisperject	Medication "shot out before patient could inject"	Wasted dose	³⁰³
Whisperject	Needle "squirted out liquid" on loading/handling	Wasted dose	²⁴³
HUMIRA pen	Pen released dose when patient pulled away to check it	Dose wasted; liquid on floor	²⁷³
Accu-Chek Linkassist Plus Insertion Device	Device ejected infusion set unintentionally → accidental fingerstick	Needlestick injury	³⁴

The most clinically serious case in the record set: The Whisperject misfire ¹¹¹ caused tissue necrosis and a staph infection requiring months of wound care. The mechanism combined a "misfire" (forceful, premature release) with an injection that was "too fast," traumatizing subcutaneous tissue. A report explicitly coded this as "device use error" ¹¹¹¹⁴⁸. A complicating factor: the patient had the underlying condition (relapsing multiple sclerosis) that may have affected motor control.

2.4 Needle Cap / Safety Mechanism Failure (Including Cap-Not-Removed Errors)

Device	Issue	Outcome	Source
BD Autoshield Duo Safety Pen Needle	Safety shield not deployed correctly after use	Needlestick risk; user error confirmed	³¹⁸
BD Nano Ultra-Fine Pen Needles	Inner shield and tear-drop label missing from returned samples; bent patient-end cannula	Sterility breach; contamination risk	⁶⁴
EpiPen Jr	Grey cap pulled with needle pointing away from body; needle ejected from black cap	Needlestick	¹⁰⁰
Epinephrine autoinjector (generic, DMEPA study)	Failure to remove needle cap before injection	Dose not delivered; 3 of X study participants ⁴¹¹	⁴¹¹

FDA guidance explicitly uses cap-removal failure as its worked example of a critical task use error: the URRA draft guidance presents a case where failure to remove the needle cap causes delayed emergency administration — a potentially life-threatening error for emergency-use autoinjectors ³¹⁰. DMEPA's epinephrine autoinjector review identified the cap-removal task as a critical task specifically because timing matters in anaphylaxis ⁴¹⁰.

2.5 Failure to Activate / Button/Plunger Problems

MAUDE findings — coded as Malfunction but often reflect user-device mismatch:

Device	Failure	Note	Source
Whisperject	Button would not depress; could not activate	Disease-related motor/dexterity issues possible	¹⁴⁵
Whisperject	Button stuck; nothing happened when pressed	Unclear device vs. user	²⁵⁶²⁹⁹³⁰¹
Whisperject	Device would not set properly; patient injected with syringe instead	User setup error possible	²⁹⁴
BD Autoshield Duo Safety Pen Needle	"Difficult or delayed activation"	Root cause undetermined	⁴⁴
BD Nano Ultra-Fine Pen Needle	Had to "press harder to inject"	Blocked/kinked needle	⁹⁷
EpiPen	Patient "hit thigh multiple times," hit EpiPen on sink and car dashboard trying to get it to work	Misunderstanding of EpiPen operation; device may have malfunctioned	¹¹⁰

Clinical concern: For life-threatening conditions (anaphylaxis, severe pain crises), failure to activate an autoinjector—even for 30–60 seconds—can have serious consequences. DMEPA noted that for emergency-use autoinjectors, most or all tasks may be critical tasks due to time-sensitivity ¹⁰²².

2.6 Improper Injection Technique (Wrong Angle, Wrong Site, Wrong Tissue Depth)

Device	Error	Outcome	Source
Autoject II / glass syringe	Needle hit muscle (thigh); syringe shattered	Thigh soreness; syringe fragment risk	⁹⁵
BD pen needle (unspecified)	Installed at angle on pen → needle bent/broke	No serious injury; embedded fragment risk	⁵²⁵³
Whisperject Autoinjector	Device use error described; patient with MS may have had impaired technique	Injection-site pain, bruising, seroma, necrosis, wound	¹¹¹¹⁴⁸
Epinephrine autoinjector (DMEPA study)	Failure to insert needle into muscular area of body/thigh	Critical task failure ⁴¹¹	⁴¹⁰⁴¹¹

The 510(k) records for Whisperject and SHL DAI autoinjectors both required verification of activation force, needle extension distance, injection time, and completeness of injection ⁴⁰⁴⁴⁰⁵ — all parameters directly linked to proper user technique. The SHL DAI explicitly incorporated a safety mechanism to prevent inadvertent activation and automatic needle recovery post-injection to reduce technique-related use errors ⁴⁰⁵.

2.7 Device Reuse of Single-Use Autoinjectors

Device	Issue	Outcome	Source
BD pen needles (multiple variants)	Needle clogging, bent needles, breakage — often from reuse or repeated installation	Delivery failure, needle fragment retained	⁴⁸⁵⁰⁵⁶⁵⁷
Whisperject Autoinjector	Needles bent; injector "doesn't stay together" — patient using needles multiple times	Unable to use device for over 2 weeks	²⁹⁸
BD Nano Ultra-Fine Pen Needle	Sterility breach — inner shield missing from returned samples	Infection risk from compromised sterility	⁶⁴

Important context: Manufacturer guidance for all pen needles instructs single-use only. Bent needles and delivery failures are strongly associated with multi-use in clinical practice. FDA's IFU labeling guidance requires explicit "do not reuse" instructions for single-use devices ¹¹⁹¹²⁰.

2.8 Activation Force / Dexterity Mismatch

Beyond simple button-failure reports, several records hint at a user–device capability mismatch: autoinjectors require adequate grip strength and hand function, and many are prescribed to patients with conditions (rheumatoid arthritis, MS, Parkinson's) that impair exactly those capabilities.

Specific MAUDE examples:

Whisperject patient with MS reporting repeated inability to press the button ¹⁴⁵²⁵²²⁵⁶
A patient using a nail file to roughen the device wings because they were "too small and smooth" (explicitly coded as device use error) ¹⁴⁸
Multiple Whisperject reports of patients with the underlying MS-related motor impairment being unable to complete the injection ²⁹⁴²⁹⁹³⁰¹

Regulatory context: FDA guidance notes that use-related risks should be assessed in the context of the intended user population and their range of physical capabilities ²¹¹²¹⁷. For RA and MS patients using TNF-inhibitor or glatiramer acetate autoinjectors, the very disease being treated can impair the motor function required to operate the device.

2.9 Confusion / Incorrect Device Setup

Device	Error	Source
Autoject2	Patient used Autoject2 instead of the Whisperject (wrong device); coded as "improper or incorrect procedure"	³¹⁷
Whisperject	Patient attempted to open and repair device herself after repeated misfires	³⁰⁰
EpiPen	Patient hit EpiPen against hard surfaces (sink, dashboard) trying to force needle exposure	¹¹⁰
Epinephrine autoinjector (DMEPA study)	Participants applied EpiPen-style muscle memory to a different device design → negative transfer → plunger not fully depressed	⁴¹⁰
HUMIRA pen	Patient using HUMIRA pen to give insulin injection	²⁸¹

3. Comparison: Use Errors vs. Pure Device Defects

The distinction is critical for regulatory submissions and postmarket surveillance. The following table organizes events by primary attribution:

Category	Clearest Device Defects	Clearest Use Errors
Needle breakage	Manufacturing burr/hook on needle tip ¹⁰⁴; sterility breach with bent cannulas from production ⁶⁴	Needle installed at angle → bent during pen attachment; user error per manufacturer investigation ⁴⁶⁵²⁵³
Dose not delivered	Needle not hollowed out from manufacturing ⁶¹; seal failure causing leak before use ³⁴⁶	Humira pen removed prematurely before click ²⁷³; Whisperject likely incorrect use ²⁹¹
Premature activation	Whisperject mechanical misfire (device jammed after firing) ¹¹¹	Accu-Chek ejection during user handling ³⁴; dose released when Humira pen lifted ²⁷³
Failure to activate	Whisperject button stuck (mechanical jam) ²⁵³³⁰⁴	Patient didn't press hard enough; used EpiPen technique on different device ⁴¹⁰
Needle in skin	EpiPen needle hooked (manufacturing burr) ¹⁰⁴	Improper removal angle causing needle bending ¹⁰⁷
Dose leak/waste	Cracked barrel/hub from manufacturing ⁴⁷⁵⁴	Patient-end cannula bent on injection (technique-related) ⁴⁶; Whisperject opened/tampered with by patient ³⁰⁰

Key observation: The MAUDE record corpus for autoinjectors shows that many events reported as "Malfunction" contain clear use-error components when narrative text is reviewed. Root-cause ambiguity is high because:

Manufacturers frequently cannot confirm the defect (no samples returned)
Reporters (often healthcare professionals or pharmacovigilance staff) default to "device failure" framing
A single event often reflects both: a device whose design is susceptible to a user error mode

In the FDA drug review database, DMEPA's assessments of HF validation studies for adalimumab autoinjectors (IDACIO, YUFLYMA, BIMZELX) and BYDUREON BCISE consistently found critical task failures in formal human factors validation studies — failures that by definition are not device defects, since the device operated as designed ²⁸²⁹³⁰³³. This is perhaps the clearest evidence that use errors are a systemic problem for the autoinjector class.

4. DMEPA / FDA Drug Review Critical Task Failures

The following autoinjector combination products had FDA-documented critical-task use-error findings in their New Drug Application or Biologics License Application reviews:

Product	Active Ingredient	DMEPA Finding	Source
IDACIO (adalimumab-aacf) autoinjector	Adalimumab biosimilar	HF validation studies showed "several use errors/close calls/use difficulties with critical tasks that may result in harm to the patient"; manufacturer required to revise user interface	²⁸²⁹
BIMZELX (bimekizumab-bkzx) autoinjector	Bimekizumab	HF validation found "failures, close calls, and use difficulties with critical tasks"; packaging and labeling had areas of vulnerability likely to lead to medication errors	³⁰
YUFLYMA (adalimumab-aaty) autoinjector	Adalimumab biosimilar	HF supported safe use overall, but labeling/packaging had "areas of vulnerability that may lead to medication errors"	³¹
BYDUREON BCISE (exenatide synthetic) autoinjector	Exenatide	HF validation showed failures on critical tasks; root-cause analysis indicated additional labeling changes were needed; no re-study required	³³
HADLIMA (adalimumab-bwwd, PushTouch) autoinjector	Adalimumab biosimilar	Certain IFU sections needed revision from a medication error prevention perspective	²⁷
Epinephrine autoinjector (unnamed applicant, DMEPA review)	Epinephrine	HF validation did not demonstrate safe and effective use; failures on all 5 critical tasks noted; study methodology also found flawed	⁴¹⁰⁴¹¹

5. Critical Use-Error Task Taxonomy (Synthesized Across Sources)

Based on FDA guidance and MAUDE evidence, the dominant autoinjector use-error modes can be organized into a formal task-based taxonomy:

Pre-Injection Errors

Error Mode	Clinical Impact	Evidence Base
Failure to remove needle cap/tip cover	Dose completely blocked; emergency medication not delivered	DMEPA (3 failures); URRA guidance worked example ³⁴¹⁰⁴¹¹
Device not at room temperature / improperly stored	Crystallized drug, increased injection pain, incomplete dissolution	FDA IFU labeling guidance requirement ¹²¹¹²²
Wrong device selected	Wrong drug or dose delivered	MAUDE: Autoject2 used instead of Whisperject ³¹⁷; HUMIRA pen used for insulin ²⁸¹
Needle installed at angle on pen	Needle bends/breaks on injection; dose not delivered; needle embedded in tissue	MAUDE: BD pen needle reports; manufacturer root cause: user error ⁴⁶⁵²⁵³

Injection-Phase Errors

Error Mode	Clinical Impact	Evidence Base
Insufficient pressure on skin	Needle does not penetrate; dose not delivered	MAUDE: Humira pen ²⁷⁴; DMEPA: needle insertion failure ⁴¹¹
Wrong injection site	Intramuscular vs. subcutaneous delivery; PK altered	DMEPA critical task ⁴¹¹; MAUDE: thigh muscle hit, syringe shattered ⁹⁵
Wrong injection angle	Tissue trauma, altered drug absorption, needle damage	MAUDE: needle hit muscle ⁹⁵; guidance: angle affects PK ²¹¹
Premature device removal (before click/end signal)	Partial or complete dose lost	MAUDE: Humira pen ²⁷³²⁸³; Whisperject ³²⁶; DMEPA: plunger failure ⁴¹¹
Failure to hold device during injection window	Incomplete injection; drug escapes from skin entry point	MAUDE: multiple Whisperject reports
Failure to fully depress plunger	Partial dose; negative transfer from other device	DMEPA: epinephrine autoinjector study ⁴¹⁰

Post-Injection Errors

Error Mode	Clinical Impact	Evidence Base
Safety guard/needle shield not deployed	Needlestick injury risk to caregiver/patient	MAUDE: BD Autoshield safety failure ⁴⁴; DMEPA concern ⁴¹¹
Failure to seek emergency care after epinephrine	Biphasic anaphylaxis risk if symptoms recur without 911/ER	DMEPA: "wait and see" behavior documented ⁴¹⁰
Device reuse	Infection, contamination, bent/broken needle on re-insertion	MAUDE: multiple pen needle records ⁴⁸⁵⁰⁵⁸; sterility breach ⁶⁴

Systemic / Behavioral Errors

Error Mode	Clinical Impact	Evidence Base
Negative transfer from other device	Wrong activation technique (press vs. hold vs. plunge)	DMEPA: EpiPen users applying wrong technique to other devices ⁴¹⁰
Physical incapacity to activate	Dose missed; patient forced to manual injection	MAUDE: MS patients with Whisperject ¹⁴⁵²⁵²²⁹⁴; RA patients with high-force devices
Improvising device modifications	Injury, device malfunction	MAUDE: patient roughening Whisperject wings with nail file ¹⁴⁸

6. Regulatory Framework: How FDA Addresses Use Errors

6.1 Use-Related Risk Analysis (URRA)

FDA's draft guidance "Purpose and Content of Use-Related Risk Analyses for Drugs, Biological Products, and Combination Products" formally defines a use error and requires sponsors to:

Systematically identify use-related hazards across all critical tasks ¹⁵²³
Estimate risk using severity and probability of harm ³
Categorize each task as critical (harm if done wrong) or noncritical ⁸²²²³
For emergency-use autoinjectors (epinephrine), consider that most or all tasks may be critical due to time-sensitivity ¹⁰
Provide a worked autoinjector example: cap-removal failure → delayed injection → harm ³

6.2 Human Factors Validation Requirements

FDA's guidance "Application of Human Factors Engineering Principles for Combination Products" sets out that:

HFE should be applied to the entire combination product, not just the device constituent ⁹¹⁷
The user interface includes packaging, labels, IFU, and training materials ⁹
FDA may evaluate HF validation data in premarket review ⁶
Residual use-related risk after validation must be analyzed and justified ⁶
Sponsors should eliminate or mitigate risks through design first, then protective measures, then labeling/training (labeling and training are least-preferred because they may be unavailable at time of use) ²¹³²¹⁶

6.3 Instructions for Use (IFU)

FDA guidance "Instructions for Use — Patient Labeling for Human Prescription Drug and Biological Products" specifies that IFU for autoinjectors must include:

Step-by-step visual instructions for device administration ¹²¹¹²²¹²⁶¹²⁸
"Important Information You Need to Know Before Injecting…" section ¹²⁴¹³⁰¹³¹

The "Technical Considerations for Pen, Jet, and Related Injectors" guidance requires that injector labeling be consistent with approved drug labeling and include patient labeling and medication guides as applicable ¹¹⁹¹²⁰.

6.4 Bridging Data and New Autoinjector Presentations

FDA's draft bridging guidance for drug-device combination products notes that when a sponsor switches from a prefilled syringe to an autoinjector, the new user interface may:

Change injection technique, angle, and tissue depth in ways that affect the PK profile and local adverse reaction profile ²¹¹¹³
Require new HF validation data unless the user interface is proven equivalent ⁴¹³
Require design verification and simulated-use testing ¹

6.5 510(k) Device Design Expectations

510(k) reviews for autoinjectors (WhisperJECT, SHL DAI) evaluated performance parameters directly linked to use-error risk:

Activation force (must be achievable by target user population)
Needle extension distance (determines tissue depth)
Injection time (too fast → tissue trauma; too slow → patient removes early)
Completeness of injection ⁴⁰⁴⁴⁰⁵

The SHL DAI incorporated explicit use-error-reduction design features:

Safety mechanism to prevent inadvertent activation ⁴⁰⁵
Automatic needle recovery after injection (reduces needlestick from removed device) ⁴⁰⁵
Locking tabs preventing disassembly post-connection ⁴⁰⁵
Self-disabling after a single use ⁴⁰⁵

7. Warning Letters Context

Searched FDA warning letters did not return records explicitly citing autoinjector use errors at named facilities. The closest relevant letters involved:

IFU adequacy failures where clinics were not informed of correct instructions for use after complaint signals ¹⁶¹
Risk analysis inadequacy where user errors were attributed to labeling issues not properly evaluated in the hazard analysis ¹⁶⁰
Promotional material oversimplification of administration process, omitting material dosing information ¹⁵⁵

This is consistent with the general pattern that FDA warning letters tend to address GMP/QSR violations (manufacturing controls, complaint handling, CAPA) rather than patient use-error outcomes per se.

8. Illustrative MAUDE Case Examples (Representative Detail)

Case A — Whisperject Misfire Causing Skin Necrosis ⁹⁶¹¹¹

A patient using Whisperject autoinjector for a self-injection reported the device "misfired" and then "fired the injection more forcefully than usual, releasing the medication too quickly" into the abdomen. The device subsequently jammed, and the patient had to complete the injection manually. Outcomes: bleeding, bruising, blood blister, dead skin/sloughing, skin necrosis with black scar tissue, wound requiring wound clinic care, debridement, antibiotics, and a staph infection. Coded as Injury. Narrative explicitly includes the code phrase "device use error." The patient with relapsing MS and potential motor impairment was a contributing factor.

Case B — HUMIRA Pen Dose Lost on Premature Removal ²⁷³

Patient pressed HUMIRA pen against skin, waited, heard no click confirming injection completion, and pulled the pen away to check it. At the moment of removal, the pen released its full dose — liquid spilled on the floor. No medication was delivered. No serious patient injury. Coded as Malfunction. The mechanism (removing the device before the end-of-injection indicator activates) is a classic incomplete-holding use error, yet the report is framed as a device failure.

Case C — BD Pen Needle Bent Needle / Needlestick Cluster ⁴⁶⁵²⁵³

Multiple reports for BD Ultra-Fine and Nano Ultra-Fine pen needles described the rear (non-patient) cannula bending and breaking when the needle was installed on the pen device at an angle. Manufacturer investigations explicitly concluded root cause was user error — improper installation technique — and cited insufficient patient training as a systemic contributing factor. Several resulted in embedded needle fragments requiring ER/X-ray evaluation ⁵¹⁵⁹.

Case D — EpiPen Cap Ejection ¹⁰⁰

EpiPen Jr user pulled the grey cap off with the needle pointing away from the body; the needle ejected from the black cap and caused an accidental needlestick. This is a widely recognized use error pattern for the EpiPen: the "blue to the sky, orange to the thigh" rule is designed to prevent exactly this — but without reinforced training, users sometimes orient the device incorrectly.

Case E — DMEPA Study: Epinephrine Autoinjector Critical Task Failures ⁴¹⁰⁴¹¹

In an FDA DMEPA-reviewed human factors validation study, the intended device was studied in an emergency-simulation scenario with naive trained lay users and trained patients. Critical task failures identified:

Cap not removed: 3 participants (2 naive trained lay users at first injection; 1 trained patient at second injection)
Needle not inserted into muscular area: documented failures
Plunger not fully depressed: linked to negative transfer from EpiPen use
Needle guard not properly deployed: created needlestick risk
Failure to call 911/ER: patients said they would wait to see if symptoms improved

DMEPA concluded: the study did not demonstrate safe and effective use by the intended population.

Case F — Autoject Syringe Shatter ⁹⁵

Patient using Autoject II for glass syringe pressed device to left thigh and activated. The needle hit muscle, the syringe shattered, and needle remained in the thigh. Coded as Injury. Combines an injection-technique error (intramuscular hit) with potential device-design interaction.

9. Frequency Comparison: Use Errors vs. Pure Device Defects

Precise quantitative separation is impossible from the current MAUDE record set due to root-cause ambiguity, but the qualitative pattern is clear:

Signal Type	MAUDE Volume Observed	Key Examples
Use errors (primary attribution)	Majority of "Malfunction" narrative cases	HUMIRA premature removal, BD pen needle angle installation, Whisperject improper technique, epinephrine DMEPA study failures
Mixed (use error + device susceptibility)	Multiple Injury and Malfunction records	Whisperject misfire (device AND user error coded), Autoject syringe shatter
Pure device defects	Minority of records with confirmed manufacturing investigation	Bent/hooked needle from production ¹⁰⁴; sterility breach from packaging defect ⁶⁴; Autoject dose loss from confirmed manufacturing defect ²⁵⁷

In formal HF validation studies reviewed by DMEPA, critical task use-error failures were documented across all 5–6 assessed autoinjector products, while pure device failures (operating-as-designed) were not the reported finding. This strongly suggests that for autoinjectors used in real-world conditions, use errors are the dominant source of performance failures, with pure device defects being a smaller but non-negligible contributor.

10. Conclusions

Use errors are pervasive and systematically undercounted in MAUDE. The absence of a discrete "use error" event type means most use-error events are coded as Malfunction or Injury, requiring narrative review to detect.
The most common use-error modes are: (a) incomplete dose from premature device removal or insufficient skin contact, (b) failure to remove needle cap, (c) needle installation at incorrect angle (pen needles), (d) failure to fully activate/depress, (e) accidental premature activation, and (f) failure to navigate safety mechanisms post-injection.
Emergency-use autoinjectors carry the highest use-error stakes. DMEPA data for an epinephrine autoinjector showed critical task failures across all categories in a formal study, and the guidance explicitly identifies time-sensitive devices as requiring near-universal critical task coverage ¹⁰⁴¹⁰⁴¹¹.
DMEPA/FDA drug reviews are the richest source of structured use-error evidence. The IDACIO, BIMZELX, YUFLYMA, BYDUREON BCISE, HADLIMA, and epinephrine autoinjector reviews all documented critical task failures — information that would be largely invisible in MAUDE alone ²⁷²⁸²⁹³⁰³¹³³⁴¹⁰⁴¹¹.
Device design and use errors are not independent. Susceptibility to user mistakes is a design property. Safety features (automatic needle recovery, inadvertent-activation prevention, clear end-of-injection indicators, force-appropriate actuation) can substantially reduce use-error rates — and FDA expects this hierarchy: design first, then labeling ²¹³²¹⁶⁴⁰⁵.
Population-device mismatch is underappreciated. Many autoinjector drugs (TNF inhibitors, glatiramer acetate, GLP-1 agonists) are prescribed to patients whose disease simultaneously impairs the motor and cognitive capabilities required for device operation ¹⁴⁵¹⁴⁸²⁹⁴.

All citations [N] correspond to source documents in FDA MAUDE, FDA Drugs@FDA, FDA guidance, and FDA 510(k) databases as returned by the search queries above.

Autoinjector Use Errors vs Device Defects: A Comprehensive FDA Analysis