Side Effects of Microzide (hydrochlorothiazide)

Microzide (hydrochlorothiazide) is a diuretic used to treat excessive fluid accumulation and swelling (edema) of the body caused by heart failure, cirrhosis, chronic kidney failure, corticosteroid medications, and nephrotic syndrome. It also is used alone or in conjunction with other blood pressure lowering medications to treat high blood pressure. 

Microzide can be used to treat calcium-containing kidney stones because it decreases the amount of calcium excreted by the kidneys in the urine and thus decreases the amount of calcium in urine to form stones. Although Microzide is approved for treating edema in cirrhosis of the liver, it is rarely used because of the availability of other diuretics that are more effective.

Common side effects of Microzide include

• weakness,
• low blood pressure,
• light sensitivity (rash caused by sunlight),
• impotence,
• nausea, and
• abdominal pain.

Serious side effects of Microzide include

• electrolyte disturbances,
• pancreatitis,
• yellowing skin and eyes (jaundice), and
• life-threatening allergic reaction (anaphylaxis).

Drug interactions of Microzide include lithium, because Microzide reduces the elimination of lithium by the kidneys and can lead to lithium toxicity.

• Nonsteroidal anti-inflammatory drugs (NSAIDs), for example, ibuprofen, may reduce the blood pressure lowering effects of Microzide.
• Blood sugar levels can be elevated by Microzide, necessitating adjustment in the doses of medications that are used for treating diabetes.
• Combining Microzide with corticosteroids may increase the risk for low levels of blood potassium and other electrolytes.
• Low blood potassium (hypokalemia) can increase the toxicity of digoxin. Cholestyramine and colestipol bind to Microzide and reduce its absorption from the gastrointestinal tract by 43% to 85%. 

There are no adequate studies of Microzide in pregnant women. Thiazide diuretics may increase the risk of fetal or neonatal jaundice, low platelet levels, and possibly other adverse reactions that have occurred in adults. 

Microzide is excreted in breast milk. Intense diuresis using Microzide may reduce the production of breast milk. Otherwise Microzide is considered safe to use during breastfeeding if required by the mother. Consult your doctor before breastfeeding.

Side effects of hydrochlorothiazide include

• weakness,
• low blood pressure,
• light sensitivity (rash caused by sunlight),
• impotence,
• nausea, and
• abdominal pain.

More serious side effects include

• electrolyte disturbances,
• pancreatitis,
• jaundice, and
• anaphylaxis (a life-threatening allergic reaction).

Patients allergic to sulfa may also be allergic to hydrochlorothiazide because of the similarity in the chemical structure of the medications.

Hydrochlorothiazide can aggravate kidney dysfunction and is used with caution in patients with kidney disease. Hydrochlorothiazide can lower blood potassium, sodium, and magnesium levels. Low potassium and magnesium levels can lead to abnormalities in heart rhythm, especially in patients already taking digoxin (Lanoxin). During hydrochlorothiazide treatment, supplementation with potassium is common to prevent low potassium levels.

Blood uric acid levels can increase during hydrochlorothiazide treatment, and this elevation may cause an episode of acute gout in some individuals. Thiazide diuretics may increase blood sugar (glucose) levels and precipitate diabetes.

The adverse reactions associated with hydrochlorothiazide have been shown to be dose related. In controlled clinical trials, the adverse events reported with doses of 12.5 mg hydrochlorothiazide once daily were comparable to placebo. The following adverse reactions have been reported for doses of hydrochlorothiazide 25 mg and greater and, within each category, are listed in the order of decreasing severity.

• Body as a whole: Weakness.
• Cardiovascular: Hypotension including orthostatic hypotension (may be aggravated by alcohol, barbiturates, narcotics or antihypertensive drugs).
• Digestive: Pancreatitis, jaundice (intrahepatic cholestatic jaundice), diarrhea, vomiting, sialadenitis, cramping, constipation, gastric irritation, nausea, anorexia.
• Hematologic: Aplastic anemia, agranulocytosis, leukopenia, hemolytic anemia, thrombocytopenia.
• Hypersensitivity: Anaphylactic reactions, necrotizing angiitis (vasculitis and cutaneous vasculitis), respiratory distress including pneumonitis and pulmonary edema, photosensitivity, fever, urticaria, rash, purpura.
• Metabolic: Electrolyte imbalance (see PRECAUTIONS), hyperglycemia, glycosuria, hyperuricemia.
• Musculoskeletal: Muscle spasm.
• Nervous System/Psychiatric: Vertigo, paresthesia, dizziness, headache, restlessness.
• Renal: Renal failure, renal dysfunction, interstitial nephritis (see WARNINGS).
• Skin: Erythema multiforme including Stevens-Johnson syndrome, exfoliative dermatitis including toxic epidermal necrolysis, alopecia.
• Special Senses: Transient blurred vision, xanthopsia.
• Urogenital: Impotence.

Whenever adverse reactions are moderate or severe, thiazide dosage should be reduced or therapy withdrawn.

When given concurrently the following drugs may interact with thiazide diuretics:

• Alcohol, barbiturates, or narcotics: potentiation of orthostatic hypotension may occur.
• Antidiabetic drugs: (oral agents and insulin) dosage adjustment of the antidiabetic drug may be required.
• Other antihypertensive drugs: additive effect or potentiation.
• Cholestyramine and colestipol resins: Cholestyramine and colestipol resins bind the hydrochlorothiazide and reduce its absorption from the gastrointestinal tract by up to 85 and 43 percent, respectively.
• Corticosteroid, ACTH: intensified electrolyte depletion, particularly hypokalemia.
• Pressor amines (e.g., norepinephrine): possible decreased response to pressor amines but not sufficient to preclude their use.
• Skeletal muscle relaxants, nondepolarizing (e.g., tubocurarine): possible increased responsiveness to the muscle relaxant.
• Lithium: generally should not be given with diuretics. Diuretic agents reduce the renal clearance of lithium and greatly increase the risk of lithium toxicity. Refer to the package insert for lithium preparations before use of such preparations with MICROZIDE (hydrochlorothiazide capsule) .
• Non-steroidal anti-inflammatory drugs: In some patients, the administration of a non-steroidal anti-inflammatory agent can reduce the diuretic, natriuretic, and antihypertensive effects of loop, potassium-sparing and thiazide diuretics. When MICROZIDE (hydrochlorothiazide capsule) and non-steroidal anti-inflammatory agents are used concomitantly, the patients should be observed closely to determine if the desired effect of the diuretic is obtained.

Drug/Laboratory Test Interactions

• Thiazides should be discontinued before carrying out tests for parathyroid function.