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Equaline Acid Reducer Side Effects

Generic name: cimetidine

Medically reviewed by Last updated on Nov 21, 2023.

Note: This document contains side effect information about cimetidine. Some dosage forms listed on this page may not apply to the brand name Equaline Acid Reducer.

Applies to cimetidine: oral liquid and tablets, parenteral injection, parenteral injection for iv infusion only.

Side effects include:

Headache, dizziness, somnolence, diarrhea.

With ≥1 month of therapy: gynecomastia.

With IM therapy: transient pain at injection site.

For Healthcare Professionals

Applies to cimetidine: compounding powder, intravenous solution, oral liquid, oral tablet.


Very common (10% or more): Increased plasma creatinine (up to 11%)

Rare (0.01% to 0.1%): Interstitial nephritis[Ref]

Interstitial nephritis cleared with drug withdrawal.

Creatinine elevations usually occurred during the first week of treatment and were typically non-progressive, with values returning to pretreatment levels during therapy or up to 1 week after stopping treatment.[Ref]


Pancreatitis cleared with drug withdrawal.[Ref]

Common (1% to 10%): Constipation, diarrhea, flatulence, nausea, vomiting

Rare (0.01% to 0.1%): Acute pancreatitis/pancreatitis[Ref]


Common (1% to 10%): Musculoskeletal pain, myalgia/reversible myalgia

Rare (0.01% to 0.1%): Arthralgia/reversible arthralgia, exacerbation of joint symptoms, polymyositis[Ref]

Nervous system

Headaches occurred more frequently in patients given 1600 mg/day compared to patients given 800 mg/day.

Somnolence and dizziness were usually mild and have been reported in patients receiving 800 to 1600 mg/day.[Ref]

Common (1% to 10%): Dizziness, drowsiness, headache[Ref]


Common (1% to 10%): Rash/skin rashes

Rare (0.01% to 0.1%): Hypersensitivity vasculitis

Very rare (less than 0.01%): Epidermal necrolysis, erythema multiforme, generalized exfoliative erythroderma, reversible alopecia, severe generalized skin reactions, Stevens-Johnson syndrome

Frequency not reported: Severe skin rash[Ref]

Hypersensitivity vasculitis usually cleared with drug withdrawal.[Ref]


Fever cleared with drug withdrawal.[Ref]

Common (1% to 10%): Tiredness

Rare (0.01% to 0.1%): Fever[Ref]


Uncommon (0.1% to 1%): Confusional state, depression, hallucination

Frequency not reported: Agitation, anxiety, disorientation, mental confusion, psychosis[Ref]

Confusional states occurred within 2 to 3 days of starting treatment, were reversible within 3 to 4 days of stopping treatment and were more commonly reported in elderly patients and/or ill patients (e.g., renal dysfunction, organic brain syndrome).[Ref]


Hepatitis and serum transaminase level elevations cleared with drug withdrawal.

Fatal hepatic effects have occurred with other histamine-2 receptor antagonists.

Severe parenchymal injury is considered highly unlikely due to the predominance of cholestatic features.

There was a report of biopsy-proven periportal hepatic fibrosis in a patient receiving this drug.[Ref]

Uncommon (0.1% to 1%): Hepatitis, reversible liver damage

Rare (0.01% to 0.1%): Cholestatic effects, increased serum transaminases, mixed cholestatic-hepatocellular effects

Very rare (less than 0.01%): Fatal hepatic effects

Frequency not reported: Periportal hepatic fibrosis, severe parenchymal injury[Ref]


Leukopenia and/or thrombocytopenia were reversible with withdrawal of treatment.

Agranulocytosis/decreased white blood cell counts have been reported, with some events recurring upon rechallenge. These events were more commonly reported in patients with serious concomitant illnesses and/or those who received drugs/treatments known to produce neutropenia.[Ref]

Uncommon (0.1% to 1%): Leukopenia

Rare (0.01% to 0.1%): Agranulocytosis, aplastic anemia, decreased white blood cell counts, pancytopenia, thrombocytopenia

Very rare (less than 0.01%): Immune hemolytic anemia[Ref]


Uncommon (0.1% to 1%): Tachycardia

Rare (0.01% to 0.1%): Atrioventricular (AV) heart block/heart block, sinus bradycardia[Ref]


Uncommon (0.1% to 1%): Reversible impotence

Rare (0.01% to 0.1%): Urinary retention

Very rare (less than 0.01%): Galactorrhea[Ref]

Urinary retention cleared with drug withdrawal.[Ref]


Uncommon (0.1% to 1%): Gynecomastia[Ref]


Rare (0.01% to 0.1%): Allergic reactions, anaphylaxis[Ref]

Allergic reactions and anaphylaxis usually cleared with drug withdrawal.[Ref]


Very rare (less than 0.01%): Strongyloidiasis hyperinfection[Ref]


Frequency not reported: Pneumonia[Ref]

In a large epidemiological study, it was suggested that patients taking histamine-2-receptor antagonists had an increased adjusted relative risk of 1.63 (95% confidence interval of 1.07 to 2.48) of developing pneumonia compared to patients who stopped treatment. However, causal relationship between H2RA use and pneumonia has not been established.[Ref]

Frequently asked questions


1. (2001) "Product Information. Tagamet (cimetidine)." SmithKline Beecham

2. (2002) "Product Information. Tagamet HB (cimetidine)." SmithKline Beecham

3. Cerner Multum, Inc. "UK Summary of Product Characteristics."

4. Cerner Multum, Inc. "Australian Product Information."

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.