Iohexol side effects: what 8,244 FDA adverse event reports show

Iohexol · 996 reaction terms · 25,725 drug–reaction co-reports · data 2026-09-14

Drug class

Radiographic Contrast Agent

FDA label (Established Pharmacologic Class) · compare the class

Who reports

8,244 reports · 80% serious · 488 with death outcome · 56% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Iohexol is a radiographic contrast agent indicated for intrathecal, intra-arterial, intravenous, oral, rectal, intraarticular and body cavity imaging procedures in adults and pediatric patients. ( 1 ) 1.1 Intrathecal Procedures ‡ Iohexol injection is i.

FDA label, Indications and Usage

What it is

Iohexol, USP is a nonionic radiographic contrast agent available as: Iohexol injection for intrathecal, intra-arterial, intravenous, oral, rectal, intraarticular and body cavity use.

FDA label, Description section

Boxed warning

RISKS ASSOCIATED WITH INTRATHECAL ADMINISTRATION OF IOHEXOL INJECTION 140 mg IODINE/mL and 350 mg IODINE/mL Use only the iohexol, iodine concentrations and presentations recommended for intrathecal procedure [see Dosage and Administration (2.2 , 2.8) ].

FDA label

How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation. Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)? That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.

Causality screen of the 40 strongest signals

Labeled adverse reaction 8Labeled (related wording) 8Not in label — unassessed 24

What the badges mean

Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.

Strongest disproportionality signals

Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 956 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Contrast encephalopathy	58	703.0 525.8–939.9ROR 708.0 · χ² 31,214 / p <1e-300	464.8 EB05 372.8 · IC025 +6.2 3/3 methods agree	Labeled (related wording) related wording	serious n=58 · 100% clinician	no trial data cached
Contrast media allergy	247	407.2 356.6–465.0ROR 419.7 · χ² 85,765 / p <1e-300	341.2 EB05 306.9 · IC025 +7.5 3/3 methods agree	Labeled (related wording) related wording	serious n=163 · 96% clinician	no trial data cached
Contrast media reaction	267	324.4 286.1–367.8ROR 335.2 · χ² 75,951 / p <1e-300	281.6 EB05 254.4 · IC025 +7.3 3/3 methods agree	Labeled adverse reaction exact term	serious n=190	no trial data cached
Meningitis fungal	21	252.1 161.0–394.7ROR 252.7 · χ² 4,547 / p <1e-300	189.8 EB05 131.0 · IC025 +4.5 3/3 methods agree	Not in label — unassessed	serious n=21 · 100% clinician	no trial data cached
Meningitis chemical	19	239.6 149.7–383.3ROR 240.1 · χ² 3,905 / p <1e-300	179.6 EB05 121.5 · IC025 +4.3 3/3 methods agree	Not in label — unassessed	serious n=19	no trial data cached
Air embolism	20	112.3 71.8–175.6ROR 112.5 · χ² 2,006 / p <1e-300	97.7 EB05 66.8 · IC025 +4.2 3/3 methods agree	Labeled (related wording) related wording	serious n=20 · 95% clinician	no trial data cached
Anaphylactoid shock	19	107.9 68.2–170.6ROR 108.1 · χ² 1,827 / p <1e-300	93.9 EB05 63.6 · IC025 +4.1 3/3 methods agree	Labeled adverse reaction exact term	serious n=19	no trial data cached
Extravasation	133	84.4 71.1–100.2ROR 85.8 · χ² 10,528 / p <1e-300	80.8 EB05 69.9 · IC025 +5.7 3/3 methods agree	Labeled adverse reaction exact term	serious n=108 · 99% clinician	no trial data cached
Sneezing	618	72.3 66.9–78.1ROR 78.1 · χ² 42,202 / p <1e-300	70.1 EB05 65.6 · IC025 +5.9 3/3 methods agree	Not in label — unassessed	serious PRR 96.3 · 95% clinician	no trial data cached
Blood pressure immeasurable	32	54.0 38.0–76.5ROR 54.2 · χ² 1,577 / p <1e-300	51.3 EB05 38.1 · IC025 +4.3 3/3 methods agree	Not in label — unassessed	serious n=32 · 97% clinician	no trial data cached
Aneurysm ruptured	18	51.2 32.1–81.6ROR 51.3 · χ² 820 / p 1e-180	47.8 EB05 32.0 · IC025 +3.6 3/3 methods agree	Not in label — unassessed	serious n=18	no trial data cached
Tongue pruritus	16	49.1 30.0–80.6ROR 49.2 · χ² 694 / p 4e-153	45.8 EB05 29.9 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious n=13	no trial data cached
Laryngeal discomfort	12	48.8 27.6–86.4ROR 48.9 · χ² 505 / p 3e-112	44.7 EB05 27.3 · IC025 +3.1 3/3 methods agree	Labeled (related wording) related wording	serious n=12	no trial data cached
Enanthema	10	44.8 24.0–83.7ROR 44.9 · χ² 379 / p 1e-84	40.9 EB05 23.7 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached
Amaurosis	13	40.8 23.6–70.5ROR 40.8 · χ² 458 / p 7e-102	38.1 EB05 23.7 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious n=13	no trial data cached
Nasal pruritus	19	39.5 25.1–62.2ROR 39.6 · χ² 665 / p 6e-147	37.6 EB05 25.4 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious n=12	no trial data cached
Local anaesthetic systemic toxicity	15	37.3 22.4–62.1ROR 37.4 · χ² 487 / p 2e-108	35.3 EB05 22.7 · IC025 +3.2 3/3 methods agree	Not in label — unassessed	serious n=15	no trial data cached
Resuscitation	17	26.2 16.2–42.2ROR 26.2 · χ² 383 / p 2e-85	25.2 EB05 16.6 · IC025 +3.1 3/3 methods agree	Labeled adverse reaction exact term	serious n=17	no trial data cached
Nasal obstruction	17	23.6 14.6–38.0ROR 23.7 · χ² 343 / p 9e-77	22.8 EB05 15.0 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious n=17	no trial data cached
Laryngeal oedema	55	22.9 17.6–29.9ROR 23.1 · χ² 1,122 / p 3e-246	22.6 EB05 18.0 · IC025 +3.8 3/3 methods agree	Labeled adverse reaction exact term	serious n=55 · 100% clinician	no trial data cached
Oral pruritus	20	22.4 14.4–34.7ROR 22.4 · χ² 384 / p 8e-86	21.8 EB05 14.8 · IC025 +3.1 3/3 methods agree	Labeled (related wording) related wording	serious n=15 · 100% clinician	no trial data cached
Foaming at mouth	16	20.4 12.5–33.3ROR 20.4 · χ² 273 / p 1e-61	19.6 EB05 12.6 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious n=16	no trial data cached
Pulse abnormal	19	20.1 12.8–31.6ROR 20.2 · χ² 324 / p 1e-72	19.5 EB05 13.0 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious n=19	no trial data cached
Anaphylactic shock	198	19.8 17.2–22.7ROR 20.3 · χ² 3,492 / p <1e-300	19.6 EB05 17.4 · IC025 +4.0 3/3 methods agree	Labeled (related wording) related wording	serious PRR 14.1 · 91% clinician	no trial data cached
Throat tightness	208	19.7 17.2–22.6ROR 20.2 · χ² 3,656 / p <1e-300	19.6 EB05 17.4 · IC025 +4.0 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 16.3 · 97% clinician	no trial data cached
Rash maculo-papular	170	19.7 16.9–22.8ROR 20.1 · χ² 2,972 / p <1e-300	19.5 EB05 17.1 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious PRR 15.5 · ♀ 34% (drug 56%) · 98% clinician	no trial data cached
Extradural haematoma	10	19.3 10.3–35.9ROR 19.3 · χ² 154 / p 1e-35	17.9 EB05 9.4 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached
Anaphylactoid reaction	29	18.1 12.6–26.1ROR 18.2 · χ² 449 / p 6e-100	17.8 EB05 12.9 · IC025 +3.2 3/3 methods agree	Labeled adverse reaction exact term	serious n=29 · 93% clinician	no trial data cached
Kounis syndrome	16	18.1 11.1–29.6ROR 18.2 · χ² 240 / p 2e-54	17.4 EB05 10.9 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious n=16	no trial data cached
Pharyngeal paraesthesia	11	18.1 10.0–32.7ROR 18.1 · χ² 159 / p 8e-37	16.8 EB05 9.1 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious n=8	no trial data cached
Stridor	20	17.4 11.2–27.0ROR 17.4 · χ² 291 / p 2e-65	16.8 EB05 11.2 · IC025 +2.9 3/3 methods agree	Not in label — unassessed	serious n=19 · 100% clinician	no trial data cached
Dysphoria	34	17.1 12.2–24.0ROR 17.2 · χ² 496 / p 3e-110	16.8 EB05 12.5 · IC025 +3.2 3/3 methods agree	Not in label — unassessed	serious n=34 · 100% clinician	no trial data cached
Generalised erythema	37	16.4 11.9–22.7ROR 16.5 · χ² 517 / p 1e-114	16.1 EB05 12.1 · IC025 +3.2 3/3 methods agree	Labeled (related wording) related wording	serious n=36 · 97% clinician	no trial data cached
Infusion site extravasation	39	16.0 11.7–22.0ROR 16.1 · χ² 532 / p 6e-118	15.8 EB05 11.9 · IC025 +3.2 3/3 methods agree	Labeled (related wording) related wording	serious n=23 · 95% clinician	no trial data cached
Disorganised speech	11	15.6 8.6–28.1ROR 15.6 · χ² 135 / p 2e-31	14.1 EB05 7.4 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious n=11	no trial data cached
Urticaria (hives)	1,006	15.5 14.6–16.4ROR 17.5 · χ² 13,620 / p <1e-300	15.4 EB05 14.6 · IC025 +3.8 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 13.0 · 98% clinician	no trial data cached
Sensation of foreign body	50	15.3 11.6–20.1ROR 15.3 · χ² 648 / p 3e-143	15.0 EB05 11.8 · IC025 +3.3 3/3 methods agree	Not in label — unassessed	serious n=44 · ♀ 81% (drug 56%) · 96% clinician	no trial data cached
Tachypnoea	80	15.1 12.1–18.8ROR 15.2 · χ² 1,034 / p 4e-227	14.9 EB05 12.3 · IC025 +3.4 3/3 methods agree	Not in label — unassessed	serious PRR 10.7 · 96% clinician	no trial data cached
Paraplegia	17	15.1 9.4–24.3ROR 15.1 · χ² 208 / p 2e-47	14.3 EB05 8.9 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious n=17	no trial data cached
Gaze palsy	10	15.0 8.1–28.0ROR 15.1 · χ² 117 / p 2e-27	13.3 EB05 6.6 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

Most frequently reported reactions

By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Urticaria (hives)	1,006	15.5 14.6–16.4ROR 17.5 · χ² 13,620 / p <1e-300	15.4 EB05 14.6 · IC025 +3.8 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 13.0 · 98% clinician	no trial data cached
Pruritus (itching)	898	6.1 5.7–6.4ROR 6.7 · χ² 3,846 / p <1e-300	6.0 EB05 5.7 · IC025 +2.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.4 · 97% clinician	no trial data cached
Dyspnoea (shortness of breath)	777	3.5 3.3–3.7ROR 3.8 · χ² 1,420 / p <1e-300	3.5 EB05 3.3 · IC025 +1.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.3 · 95% clinician	no trial data cached
Sneezing	618	72.3 66.9–78.1ROR 78.1 · χ² 42,202 / p <1e-300	70.1 EB05 65.6 · IC025 +5.9 3/3 methods agree	Not in label — unassessed	serious PRR 96.3 · 95% clinician	no trial data cached
Erythema (skin redness)	577	7.2 6.6–7.8ROR 7.6 · χ² 3,077 / p <1e-300	7.1 EB05 6.6 · IC025 +2.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 9.7 · 96% clinician	no trial data cached
Nausea	520	1.7 1.5–1.8ROR 1.7 · χ² 147 / p 4e-34	1.7 EB05 1.6 · IC025 +0.6	Labeled adverse reaction exact term	serious PRR 1.9 · 91% clinician	no trial data cached
Vomiting	472	2.6 2.3–2.8ROR 2.7 · χ² 458 / p 7e-102	2.6 EB05 2.4 · IC025 +1.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 2.2 · 93% clinician	no trial data cached
Rash	423	2.5 2.3–2.7ROR 2.6 · χ² 381 / p 5e-85	2.5 EB05 2.3 · IC025 +1.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.5 · 94% clinician	no trial data cached
Chills	347	7.5 6.8–8.4ROR 7.8 · χ² 1,966 / p <1e-300	7.5 EB05 6.8 · IC025 +2.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 8.1 · 95% clinician	no trial data cached
Cough	331	3.0 2.7–3.3ROR 3.1 · χ² 448 / p 9e-100	3.0 EB05 2.7 · IC025 +1.4 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.4 · 93% clinician	no trial data cached
Anaphylactic reaction (severe allergic reaction)	310	14.4 12.9–16.1ROR 15.0 · χ² 3,850 / p <1e-300	14.3 EB05 13.0 · IC025 +3.6 3/3 methods agree	Labeled — boxed warning synonym match	serious PRR 10.2	no trial data cached
Acute kidney injury (sudden kidney damage)	281	4.7 4.2–5.3ROR 4.8 · χ² 819 / p 2e-180	4.7 EB05 4.2 · IC025 +2.0 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 3.3 · 91% clinician	no trial data cached
Hypotension (low blood pressure)	273	3.5 3.1–3.9ROR 3.6 · χ² 482 / p 5e-107	3.4 EB05 3.1 · IC025 +1.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 2.8 · 98% clinician	no trial data cached
Contrast media reaction	267	324.4 286.1–367.8ROR 335.2 · χ² 75,951 / p <1e-300	281.6 EB05 254.4 · IC025 +7.3 3/3 methods agree	Labeled adverse reaction exact term	serious n=190	no trial data cached
Dizziness	253	1.3 1.1–1.5ROR 1.3 · χ² 17 / p 2e-5	1.3 EB05 1.2 · IC025 +0.2	Labeled adverse reaction exact term	serious PRR 1.5 · 92% clinician	no trial data cached

Unlabeled candidate signals

These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.

Meningitis fungal — n=21, PRR 252.1
Sneezing — n=618, PRR 72.3
Blood pressure immeasurable — n=32, PRR 54.0
Rash maculo-papular — n=170, PRR 19.7
Stridor — n=20, PRR 17.4
Dysphoria — n=34, PRR 17.1
Sensation of foreign body — n=50, PRR 15.3
Tachypnoea — n=80, PRR 15.1

Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.

Common questions

What are the most reported side effects of Iohexol?

In FDA FAERS, the most frequently co-reported reaction terms for Iohexol are urticaria, pruritus, dyspnoea, sneezing, erythema, nausea. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.

Does Iohexol have an FDA boxed warning?

Yes. The current FDA label carries a boxed warning: RISKS ASSOCIATED WITH INTRATHECAL ADMINISTRATION OF IOHEXOL INJECTION 140 mg IODINE/mL and 350 mg IODINE/mL Use only the iohexol, iodine concentrations and presentations recommended for intrathecal procedure [see Dosage and Administration (2.2 , 2.8) ].

Do FAERS signals prove that Iohexol causes these side effects?

No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.

Sources & methods

FDA label via openFDA (set ID ff9456ef-c45a-450d-9004-a684af2bcc59, effective 20260630; matched on openfda.generic_name.exact:"IOHEXOL")
Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA count= aggregation, field patient.drug.openfda.generic_name.exact, 996 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction
Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
Seriousness and sex counts from openFDA count=serious, patient.patientsex, seriousnessdeath

Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.