What does the research show about h2 blockers?

H2 blockers

Trials found H2 blockers relieved heartburn, healed ulcers and esophagitis, and prevented ulcers with NSAIDs and aspirin more often than placebo, but less than proton pump inhibitors. In intensive care they cut bleeding. Cimetidine did not clear warts. The acid effect faded within two weeks of daily use. Ranitidine was withdrawn in 2020 over a contaminant.

Add to Bio HackChecked 2026-11-13

Status: Famotidine and cimetidine are prescription drugs in the US and are also sold over the counter for heartburn. The prescription famotidine label lists duodenal and gastric ulcers, reflux disease, erosive esophagitis, Zollinger-Ellison syndrome and lowering the risk of duodenal ulcer return. Zantac 360 is famotidine. FDA asked for all ranitidine to be withdrawn in 2020.
Also called: H2 receptor antagonists, H2RAs, histamine-2 blockers, acid reducers, famotidine, Pepcid, Pepcid AC, Pepcid Complete, Zantac 360, cimetidine, Tagamet, Tagamet HB, ranitidine, Zantac
Taken for: heartburn, acid reflux, GERD, stomach ulcers, duodenal ulcers, esophagitis, stomach protection with NSAIDs or aspirin, stress ulcers in intensive care, hives with antihistamines, COVID-19, warts

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help7

StrongShown to lower clinically important gut bleeding in critically ill patients, about 3 to 5 fewer per 100 at higher bleeding risk, with no clear effect on deaths.
ModerateShown to relieve heartburn more often than placebo in adults with reflux symptoms, and less often than proton pump inhibitors.
ModerateShown to heal erosive esophagitis more often than placebo, 69% against 29% at 12 weeks on famotidine 40 mg twice daily, but less often than proton pump inhibitors.Very common
ModerateShown to heal more duodenal and gastric ulcers than placebo. In one trial, 83% of duodenal ulcers healed on famotidine by 8 weeks against 45% on placebo.Very common
ModerateShown to halve duodenal ulcer return over 12 months on famotidine 20 mg at bedtime, 23% against 57% on placebo in one trial and 36% against 76% in another.Very common
ModerateShown to prevent ulcers in people on NSAIDs or low-dose aspirin. With aspirin, gastric ulcers developed in 3.4% on famotidine against 15.0% on placebo over 12 weeks.Common
LimitedSmall trials found adding ranitidine or cimetidine to diphenhydramine cleared hives more often than diphenhydramine alone. The evidence was old and at high or unclear risk of bias.

Reported risks12

ModerateThe labels report headache, dizziness and constipation in 1% or more on famotidine. On cimetidine 1,600 mg a day, headache occurred in 3.5% against 2.3% on placebo.Common
LimitedThe cimetidine label reports breast growth in men in 0.3% to 1% of patients treated a month or longer, and about 4% at the high doses used for hypersecretory conditions.Uncommon
LimitedThe cimetidine label reports low white cell counts in about 1 per 100,000 patients and agranulocytosis in about 3 per million, mostly in seriously ill people on other drugs.Rare
ModerateMixed results: one meta-analysis linked H2 blockers to about 22% higher odds of pneumonia, while intensive care analyses found no clear rise against no prophylaxis.How often is not known
LimitedThe labels warn of confusion, delirium, hallucinations and seizures reported in older people and people with reduced kidney function on famotidine, and in severely ill people on cimetidine.How often is not known
LimitedThe famotidine label reports prolonged QT intervals in people with moderate or severe kidney impairment, in whom famotidine is cleared more slowly. It gives no rate.How often is not known
LimitedSmall studies in healthy men found the acid-lowering effect of famotidine and ranitidine fell within 5 to 14 days of continuous daily dosing.How often is not known
LimitedLinked to about 25% higher odds of a vitamin B12 deficiency diagnosis with 2 or more years of H2 blocker use, in one large case-control study.How often is not known
LimitedLimited evidence: a post hoc analysis in one meta-analysis linked H2 blocker use to about 1.44 times the dementia risk in older adults.How often is not known
LimitedThe cimetidine label states it slows the liver's clearance of warfarin, phenytoin, theophylline, lidocaine and other drugs, with clinically significant effects reported for warfarin.How often is not known
LimitedThe famotidine label warns it can lower absorption of drugs that need stomach acid and may sharply raise tizanidine levels. It gives no rate.How often is not known
LimitedFDA states it asked for all ranitidine to be withdrawn in 2020 because NDMA, a probable carcinogen, built up in it. FDA found none in famotidine or cimetidine.How often is not known

What people take it for, and what was found

Shown to help7

Moderate

Heartburn relief in reflux disease

Shown to relieve heartburn more often than placebo in adults with reflux symptoms, and less often than proton pump inhibitors.

Compared with placebo [1][2]; proton pump inhibitors [1]

The numbers and sources

Effect: In people treated without an endoscopy first, the risk ratio for heartburn remission against placebo was 0.77 (95% CI 0.60 to 0.99) for H2 blockers, a value below 1 favoring the drug. In people with a normal endoscopy it was 0.84 (95% CI 0.74 to 0.95). Proton pump inhibitors did better than H2 blockers (RR 0.66 and 0.78) [1]. In a label trial in reflux without erosions, 82% improved on famotidine 20 mg twice daily, 69% on 40 mg at bedtime and 62% on placebo at 6 weeks [2].
Population: 34 randomized trials of short-term treatment in adults with reflux symptoms [1]; 376 adults with reflux symptoms and no erosions on endoscopy [2].
Sources: [1], [2]
Caveats: Only two placebo-controlled trials of H2 blockers in each group of the review [1]. Famotidine 40 mg at bedtime was not shown to beat placebo in the label trial [2].

ModerateVery common

Healing erosive esophagitis

Shown to heal erosive esophagitis more often than placebo, 69% against 29% at 12 weeks on famotidine 40 mg twice daily, but less often than proton pump inhibitors.

Compared with placebo [3][2]; proton pump inhibitors [3]; ranitidine [2]

The numbers and sources

How common: Very common: more than 1 in 10 people.
Effect: H2 blockers healed esophagitis more often than placebo (RR 0.74, 95% CI 0.66 to 0.84, a value below 1 favoring the drug), and proton pump inhibitors healed it more often than H2 blockers (RR 0.51, 95% CI 0.44 to 0.59) [3]. In a US label trial, healing at 12 weeks was 69% on famotidine 40 mg twice daily, 54% on 20 mg twice daily and 29% on placebo. In an international trial, 12-week healing was 71% on famotidine 40 mg twice daily and 60% on ranitidine 150 mg twice daily [2].
Population: 10 trials with 1,241 people comparing H2 blockers with placebo, within a review of 134 trials [3]; 318 adults in the US trial and 440 in the international trial [2].
Sources: [3], [2]
Caveats: Cochrane withdrew the 2007 review in 2011 [3]. Symptom relief did not differ between famotidine and ranitidine [2].

ModerateVery common

Healing duodenal and gastric ulcers

Shown to heal more duodenal and gastric ulcers than placebo. In one trial, 83% of duodenal ulcers healed on famotidine by 8 weeks against 45% on placebo.

Compared with placebo [2]

The numbers and sources

How common: Very common: more than 1 in 10 people.
Effect: In a US duodenal ulcer trial, 70% healed by week 4 on famotidine 40 mg at bedtime and 67% on 20 mg twice daily, against 31% on placebo. By week 8, 83% on famotidine and 45% on placebo had healed. In two gastric ulcer trials, 8-week healing was 78% and 80% on famotidine 40 mg at bedtime against 64% and 54% on placebo [2].
Population: 270 adult outpatients with duodenal ulcer, and 149 and 294 adults with gastric ulcer, in double-blind trials [2].
Sources: [2]
Caveats: Label trials. Pain relief at week 8 did not differ from placebo in the gastric ulcer trials, though pain resolved sooner on famotidine [2].

ModerateVery common

Keeping duodenal ulcers from returning

Shown to halve duodenal ulcer return over 12 months on famotidine 20 mg at bedtime, 23% against 57% on placebo in one trial and 36% against 76% in another.

Compared with placebo [2]

The numbers and sources

How common: Very common: more than 1 in 10 people.
Effect: In the US trial, cumulative duodenal ulcer recurrence within 12 months was 23% on famotidine and 57% on placebo. In the international trial it was 36% and 76% [2].
Population: 178 and 632 adults with healed duodenal ulcers in two randomized double-blind trials [2].
Sources: [2]
Caveats: Controlled trials did not go beyond one year [2].

ModerateCommon

Preventing ulcers in people taking NSAIDs or aspirin

Shown to prevent ulcers in people on NSAIDs or low-dose aspirin. With aspirin, gastric ulcers developed in 3.4% on famotidine against 15.0% on placebo over 12 weeks.

Compared with placebo [4][5]

The numbers and sources

How common: Common: between 1 in 100 and 1 in 10 people.
Effect: In NSAID users, standard-dose H2 blockers reduced endoscopic duodenal ulcers (RR 0.36, 95% CI 0.18 to 0.74) but not gastric ulcers (RR 0.73, 95% CI 0.50 to 1.09). Double-dose H2 blockers reduced gastric ulcers (RR 0.44, 95% CI 0.26 to 0.74) [4]. In people taking low-dose aspirin, at 12 weeks gastric ulcers developed in 3.4% on famotidine and 15.0% on placebo (OR 0.20), duodenal ulcers in 0.5% and 8.5% (OR 0.05), and erosive esophagitis in 4.4% and 19.0% (OR 0.20) [5].
Population: 40 randomized trials of NSAID ulcer prevention [4]; 404 adults taking aspirin 75 to 325 mg a day, without ulcers at the start [5].
Sources: [4], [5]
Caveats: Endoscopic ulcers stand in for bleeding ulcers. In the aspirin trial, 82 people without a final endoscopy were counted as normal [5].

Strong

Stress ulcer bleeding in intensive care

Shown to lower clinically important gut bleeding in critically ill patients, about 3 to 5 fewer per 100 at higher bleeding risk, with no clear effect on deaths.

Compared with placebo or no prophylaxis [6][7]; proton pump inhibitors [7]

The numbers and sources

Effect: Against placebo or no prophylaxis, H2 blockers reduced clinically important gut bleeding (OR 0.46, 95% CI 0.27 to 0.79), 4.6% fewer in the highest-risk and 3.1% fewer in high-risk patients, with no effect on mortality (OR 0.96) [6]. An updated analysis found the same direction (RR 0.67, 95% CI 0.48 to 0.94), a larger reduction with proton pump inhibitors than H2 blockers (RR 0.69), and no mortality difference (RR 0.98) [7].
Population: 72 trials with 12,660 patients [6]; 74 trials with 39,569 patients [7].
Sources: [6], [7]
Caveats: Both analyses come from the same research group, and the second updates the first. Results apply to critically ill patients only.

Limited

Hives, added to an antihistamine

Small trials found adding ranitidine or cimetidine to diphenhydramine cleared hives more often than diphenhydramine alone. The evidence was old and at high or unclear risk of bias.

Compared with diphenhydramine alone [8]

The numbers and sources

Effect: Ranitidine with diphenhydramine resolved urticaria more often than diphenhydramine alone (RR 1.59, 95% CI 1.07 to 2.36). Cimetidine alone did not improve overall symptoms more than diphenhydramine, but the combination did (RR 2.02, 95% CI 1.03 to 3.94). Sedation from baseline did not differ with famotidine or diphenhydramine [8].
Population: 144 participants in 4 small studies [8].
Sources: [8]
Caveats: The review authors called the evidence very limited and rated the studies at high to unclear risk of bias. The direct evidence is for ranitidine and cimetidine, not famotidine [8].

Mixed results1

Limited

COVID-19

Limited evidence: famotidine was not linked to fewer deaths in hospitalized COVID-19 patients, and one small outpatient trial found faster symptom improvement but no difference in time to resolution.

Compared with patients not given famotidine [9]; placebo [10]

The numbers and sources

Effect: In hospitalized patients, famotidine use was not associated with the composite of death, intubation or intensive care (HR 0.63, 95% CI 0.35 to 1.16) or with death (HR 0.67, 95% CI 0.26 to 1.73) [9]. In outpatients with mild to moderate illness, time to symptom resolution did not differ, but a 50% drop in symptom scores came at 8.2 days on famotidine and 11.4 days on placebo [10].
Population: 4 observational studies with 46,435 patients, 3,110 on famotidine [9]; 55 non-hospitalized adults, median age 35, randomized [10].
Sources: [9], [10]
Caveats: The pooled studies were observational with heterogeneity of 84% to 88% [9]. The trial was a small phase 2 study [10].

Not shown to help1

Limited

Warts (cimetidine)

Small trials found cimetidine did not clear common warts more often than placebo, with 32% cured on cimetidine against 30.7% on placebo in one trial.

Compared with placebo [11][12]

The numbers and sources

Effect: After 3 months of cimetidine 25 to 40 mg/kg daily or placebo, warts were cured in 32% (9 of 28) and 30.7% (8 of 26), with no significant difference [11]. A second double-blind trial with strict entry criteria also found cimetidine not statistically better than placebo, with a possible trend in younger people. It notes earlier uncontrolled studies reporting success [12].
Population: 70 patients with multiple warts, 54 assessed [11]; adults with recalcitrant warts [12].
Sources: [11], [12]
Caveats: Small trials. Warts often clear on their own, which open-label reports cannot separate from a drug effect [12].

Doses studied

The famotidine label trials used 40 mg at bedtime or 20 mg twice daily for duodenal ulcer, 40 mg at bedtime for gastric ulcer, 20 mg twice daily for reflux symptoms, 20 or 40 mg twice daily for erosive esophagitis, and 20 mg at bedtime to keep duodenal ulcers from returning. For Zollinger-Ellison syndrome the label starts at 20 mg every 6 hours, up to 160 mg every 6 hours [2]. The over-the-counter Zantac 360 label lists one 10 or 20 mg tablet to relieve heartburn or 10 to 60 minutes before food that causes it, no more than 2 tablets in 24 hours [13]. The cimetidine label lists 800 mg and 1,600 mg a day in its trials, and 400 mg at bedtime for up to five years to maintain healed duodenal ulcers [14].

The aspirin trial used famotidine 20 mg twice daily [5]. The wart trial used cimetidine 25 to 40 mg/kg a day for 3 months [11].

Risks

Reported risks11

ModerateCommon

Headache, dizziness and constipation

The labels report headache, dizziness and constipation in 1% or more on famotidine. On cimetidine 1,600 mg a day, headache occurred in 3.5% against 2.3% on placebo.

The numbers and sources

How common: Common: between 1 in 100 and 1 in 10 people.
Effect: Headache, dizziness and constipation occurred in 1% or more of 1,442 famotidine-treated patients in 7 trials. The label gives no placebo rate [2]. On cimetidine, headache was reported in 3.5% on 1,600 mg a day, 2.1% on 800 mg a day and 2.3% on placebo. Diarrhea, dizziness and drowsiness were each reported in about 1 in 100 [14].
Population: About 2,500 patients in 7 famotidine trials [2]; 924, 2,225 and 1,897 patients on cimetidine 1,600 mg, 800 mg and placebo [14].
Sources: [2], [14]
Caveats: Only the cimetidine label gives a placebo rate, and only for headache.

LimitedUncommon

Breast growth and impotence (cimetidine)

The cimetidine label reports breast growth in men in 0.3% to 1% of patients treated a month or longer, and about 4% at the high doses used for hypersecretory conditions.

The numbers and sources

How common: Uncommon: between 1 in 1,000 and 1 in 100 people.
Effect: Gynecomastia occurred in about 4% of patients treated for pathological hypersecretory states and 0.3% to 1% of others. Reversible impotence was reported in patients with hypersecretory disorders on high doses for at least 12 months, while in large surveillance studies at regular doses it did not exceed the general population rate [14].
Population: Patients in clinical studies and surveillance summarized in labeling [14].
Sources: [14]
Caveats: The label gives no placebo rate.

LimitedRare

Low white cells and platelets (cimetidine)

The cimetidine label reports low white cell counts in about 1 per 100,000 patients and agranulocytosis in about 3 per million, mostly in seriously ill people on other drugs.

The numbers and sources

How common: Rare: fewer than 1 in 1,000 people.
Effect: Decreased white blood cell counts occurred in about 1 per 100,000 patients, agranulocytosis in about 3 per million and low platelets in about 3 per million, with very rare aplastic anemia. Most reports were in patients with serious illnesses taking drugs known to lower blood counts [14].
Population: Postmarketing reports summarized in labeling [14].
Sources: [14]
Caveats: Rates from spontaneous reports.

LimitedHow often is not known

Confusion and other brain effects in older or kidney-impaired people

The labels warn of confusion, delirium, hallucinations and seizures reported in older people and people with reduced kidney function on famotidine, and in severely ill people on cimetidine.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: The famotidine label reports confusion, delirium, hallucinations, disorientation, agitation, seizures and lethargy in elderly patients and those with moderate or severe kidney impairment, in whom blood levels are higher [2]. The cimetidine label reports reversible confusional states, mostly in severely ill patients, usually starting within 2 to 3 days and clearing within 3 to 4 days of stopping [14].
Population: Reports summarized in labeling [2][14].
Sources: [2], [14]
Caveats: Reports with no denominator.

LimitedHow often is not known

QT prolongation with kidney impairment

The famotidine label reports prolonged QT intervals in people with moderate or severe kidney impairment, in whom famotidine is cleared more slowly. It gives no rate.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: The label states that CNS adverse reactions and prolonged QT intervals have been reported in patients with moderate and severe renal impairment, and lists a lower dose when creatinine clearance is under 60 mL/minute [2].
Population: Reports summarized in labeling [2].
Sources: [2]
Caveats: No rate or trial data are given.

LimitedStudied in menHow often is not known

The acid effect fading with daily use (tolerance)

Small studies in healthy men found the acid-lowering effect of famotidine and ranitidine fell within 5 to 14 days of continuous daily dosing.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In a crossover study, the acid-lowering effect of famotidine and ranitidine declined over 14 days of continuous use, most clearly at night, while blood drug levels stayed the same [15]. On ranitidine 150 mg four times daily, mean 24-hour stomach pH was 4.22 on day 1 and 3.28 on day 5, and time above pH 4 fell from 54.3% to 30.1% [16].
Population: 7 healthy Japanese men without H. pylori [15]; 28 healthy men [16].
Sources: [15], [16]
Caveats: Small studies in healthy volunteers measuring stomach pH, not symptoms. One studied ranitidine alone [16].

LimitedHow often is not known

Low vitamin B12

Linked to about 25% higher odds of a vitamin B12 deficiency diagnosis with 2 or more years of H2 blocker use, in one large case-control study.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: A 2 or more years' supply of H2 blockers was associated with a B12 deficiency diagnosis (OR 1.25, 95% CI 1.17 to 1.34), smaller than the association for proton pump inhibitors (OR 1.65) [18].
Population: 25,956 people with B12 deficiency and 184,199 without in one US health system [18].
Sources: [18]
Caveats: Observational. A diagnosis count reflects who was tested as well as who was low [18].

LimitedHow often is not known

Dementia

Limited evidence: a post hoc analysis in one meta-analysis linked H2 blocker use to about 1.44 times the dementia risk in older adults.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In a meta-analysis of studies in older adults, dementia risk did not differ between proton pump inhibitor and H2 blocker users (HR 1.04, 95% CI 0.89 to 1.20). In a post hoc analysis, H2 blocker use itself was associated with dementia (HR 1.44, 95% CI 1.07 to 1.93) [20].
Population: Older adults without dementia at baseline in 23 longitudinal observational studies [20].
Sources: [20]
Caveats: A post hoc result from observational studies, prone to confounding [20].

LimitedHow often is not known

Raised levels of other drugs (cimetidine)

The cimetidine label states it slows the liver's clearance of warfarin, phenytoin, theophylline, lidocaine and other drugs, with clinically significant effects reported for warfarin.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: The label lists reduced liver metabolism of warfarin-type anticoagulants, phenytoin, propranolol, nifedipine, chlordiazepoxide, diazepam, certain tricyclic antidepressants, lidocaine, theophylline and metronidazole, raising their blood levels. It reports clinically significant effects with warfarin and adverse effects with phenytoin, lidocaine and theophylline [14].
Population: Drug interaction reports and studies summarized in labeling [14].
Sources: [14]
Caveats: No rate of harm is given.

LimitedHow often is not known

Interactions with famotidine

The famotidine label warns it can lower absorption of drugs that need stomach acid and may sharply raise tizanidine levels. It gives no rate.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: The label states famotidine can reduce absorption of drugs that depend on stomach acid, such as dasatinib, delavirdine, cefditoren, fosamprenavir, atazanavir, ketoconazole and itraconazole. It describes famotidine as a weak CYP1A2 inhibitor that may substantially raise tizanidine levels, with low blood pressure, slow heart rate or drowsiness to watch for [2].
Population: Labeling statement [2].
Sources: [2]
Caveats: The tizanidine interaction was not studied clinically [2].

LimitedHow often is not known

Ranitidine withdrawn over NDMA

FDA states it asked for all ranitidine to be withdrawn in 2020 because NDMA, a probable carcinogen, built up in it. FDA found none in famotidine or cimetidine.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: FDA requested that all prescription and over-the-counter ranitidine be withdrawn immediately. It stated NDMA levels increase in ranitidine under normal storage, rise further at higher temperatures and rise as the product ages. Its testing did not find NDMA in famotidine or cimetidine [21].
Population: FDA laboratory testing of products [21].
Sources: [21]
Caveats: A regulatory action about a contaminant in one drug, not a measured harm in people.

Mixed results1

ModerateHow often is not known

Pneumonia

Mixed results: one meta-analysis linked H2 blockers to about 22% higher odds of pneumonia, while intensive care analyses found no clear rise against no prophylaxis.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In observational studies, H2 blocker use was associated with pneumonia (adjusted OR 1.22, 95% CI 1.09 to 1.36), and in randomized trials with hospital-acquired pneumonia (RR 1.22, 95% CI 1.01 to 1.48) [17]. In intensive care, the odds of pneumonia against no prophylaxis were 1.26 (95% CI 0.89 to 1.85), low certainty [6], and the risk ratio in the update was 1.07 (95% CI 0.85 to 1.37) [7].
Population: 8 observational studies and 23 randomized trials [17]; 72 and 74 trials in critically ill patients [6][7].
Sources: [17], [6], [7]
Caveats: The populations differ. The intensive care estimates had wide intervals [6][7].

Checked, no increase found2

Moderate

Fractures

Not linked to a significant rise in hip fractures in a meta-analysis of observational studies, unlike proton pump inhibitors.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: H2 blocker use was not significantly associated with hip fracture (RR 1.12, 95% CI 0.97 to 1.30), while proton pump inhibitor use was (RR 1.30) [19].
Population: 11 observational studies, mostly of older adults [19].
Sources: [19]
Caveats: Observational. Fewer studies reported H2 blocker results than proton pump inhibitor results.

Limited

Pregnancy

The famotidine label states data in pregnant women are insufficient to establish a drug-associated risk. Animal studies at high doses found no fetal harm.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: The label states available data on H2 blockers, including famotidine, are insufficient to establish a risk of major birth defects, miscarriage or other adverse outcomes. Rat and rabbit studies at up to about 243 and 122 times the human dose showed no adverse developmental effects [2].
Population: Labeling summary of human and animal data [2].
Sources: [2]
Caveats: No controlled studies in pregnant women [2].

Claims tested and not found

That cimetidine clears common warts. In a placebo-controlled trial, 32% were cured on cimetidine and 30.7% on placebo [11], and a second double-blind trial found no significant difference from placebo [12].
That famotidine lowers deaths in people hospitalized with COVID-19. Pooled observational studies found no association with death (HR 0.67, 95% CI 0.26 to 1.73) [9].
That H2 blockers raise fracture risk. Hip fracture risk was not significantly raised (RR 1.12, 95% CI 0.97 to 1.30) [19].

Sources

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Yilmaz E, Alpsoy E, Basaran E. Cimetidine therapy for warts: a placebo-controlled, double-blind study. Journal of the American Academy of Dermatology. 1996. https://doi.org/10.1016/S0190-9622(96)90279-0
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Eom CS, Jeon CY, Lim JW, et al. Use of acid-suppressive drugs and risk of pneumonia: a systematic review and meta-analysis. CMAJ. 2011. https://doi.org/10.1503/cmaj.092129
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