Adverse effects are listed in decreasing order of severity.
Hypersensitivity: Anaphylaxis, rash, urticaria, subacute cutaneous lupus erythematosus-like reactions, photosensitivity.
Cardiovascular: Arrhythmia, postural hypotension.
Metabolic: Diabetes mellitus, hyperkalemia, hypokalemia, hyponatremia, acidosis, hypercalcemia, hyperglycemia, glycosuria, hyperuricemia, hypochloremia.
Gastrointestinal: Jaundice and/or liver enzyme abnormalities, pancreatitis, nausea and vomiting, diarrhea, constipation, abdominal pain.
Renal: Acute renal failure (one case of irreversible renal failure has been reported), interstitial nephritis, renal stones composed primarily of triamterene, elevated BUN and serum creatinine, abnormal urinary sediment.
Hematologic: Leukopenia, thrombocytopenia and purpura, megaloblastic anemia.
Musculoskeletal: Muscle cramps.
Central Nervous System: Weakness, fatigue, dizziness, headache, dry mouth.
Miscellaneous: Impotence, sialadenitis.
Thiazides alone have been shown to cause the following additional adverse reactions:
Central Nervous System: Paresthesias, vertigo.
Ophthalmic: Xanthopsia, transient blurred vision.
Respiratory: Allergic pneumonitis, pulmonary edema, respiratory distress.
Other: Necrotizing vasculitis, exacerbation of lupus.
Hematologic: Aplastic anemia, agranulocytosis, hemolytic anemia.
Neonate and infancy: Thrombocytopenia and pancreatitis–rarely, in newborns whose mothers have received thiazides during pregnancy.
Skin: Erythema multiforme, including Stevens-Johnson syndrome; exfoliative dermatitis, including toxic epidermal necrolysis.
Postmarketing Experience: Non-Melanoma Skin Cancer:
Hydrochlorothiazide is associated with an increased risk of non-melanoma skin cancer. In a study conducted in the Sentinel System, increased risk was predominantly for squamous cell carcinoma (SCC) and in white patients taking large cumulative doses. The increased risk for SCC in the overall population was approximately 1 additional case per 16,000 patients per year, and for white patients taking a cumulative dose of ≥50,000 mg the risk increase was approximately 1 additional SCC case for every 6,700 patients per year.