Microzide Side Effects

Generic Name: hydrochlorothiazide

Note: This document contains side effect information about hydrochlorothiazide. Some of the dosage forms listed on this page may not apply to the brand name Microzide.

Some side effects of Microzide may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to hydrochlorothiazide: oral capsule, oral solution, oral tablet

Along with its needed effects, hydrochlorothiazide (the active ingredient contained in Microzide) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking hydrochlorothiazide:

Incidence not known
  • Abdominal or stomach pain
  • back, leg, or stomach pains
  • black, tarry stools
  • bleeding gums
  • blistering, peeling, or loosening of the skin
  • bloating
  • blood in the urine or stools
  • bloody urine
  • blue lips and fingernails
  • blurred vision
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • chest pain
  • chills
  • clay-colored stools
  • cloudy urine
  • cold sweats
  • confusion
  • constipation
  • cough or hoarseness
  • coughing that sometimes produces a pink frothy sputum
  • coughing up blood
  • cracks in the skin
  • darkened urine
  • decrease in urine output or decrease in urine-concentrating ability
  • decreased frequency or amount of urine
  • diarrhea
  • difficult, fast, or noisy breathing, sometimes with wheezing
  • difficulty with breathing
  • difficulty with swallowing
  • dizziness, faintness, or lightheadedness when getting up from a lying or sitting position
  • dry mouth
  • fast or irregular heartbeat
  • fever
  • flushed, dry skin
  • fruit-like breath odor
  • general body swelling
  • general feeling of discomfort or illness
  • general feeling of tiredness or weakness
  • greatly decreased frequency of urination or amount of urine
  • headache
  • hives
  • increased blood pressure
  • increased hunger
  • increased sweating
  • increased thirst
  • increased urination
  • indigestion
  • itching
  • joint pain, stiffness, or swelling
  • loss of appetite
  • loss of heat from the body
  • lower back or side pain
  • muscle cramps or pain
  • nausea or vomiting
  • nosebleeds
  • numbness, tingling, pain, or weakness in the hands or feet
  • pain in the joints or muscles
  • painful or difficult urination
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • pale skin
  • pinpoint red spots on the skin
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • rash
  • red, irritated eyes
  • red skin lesions, often with a purple center
  • red, swollen skin
  • redness, soreness, or itching skin
  • scaly skin
  • seizures
  • shortness of breath
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • sores, welting, or blisters
  • sugar in the urine
  • swelling of the face, fingers, legs, ankles, feet, or lower legs
  • swollen or painful glands
  • tenderness of salivary glands
  • thickening of bronchial secretions
  • tightness in the chest
  • trembling
  • troubled breathing
  • unpleasant breath odor
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • unusual weight loss
  • vomiting of blood
  • weakness and heaviness of the legs
  • weight gain
  • wheezing
  • yellow eyes or skin

Some side effects of hydrochlorothiazide may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence not known
  • Cramping
  • decreased interest in sexual intercourse
  • difficulty having a bowel movement (stool)
  • feeling of constant movement of self or surroundings
  • hair loss or thinning of the hair
  • inability to have or keep an erection
  • increased sensitivity of the skin to sunlight
  • loss in sexual ability, desire, drive, or performance
  • muscle spasm
  • pinpoint red or purple spots on the skin
  • redness or other discoloration of the skin
  • restlessness
  • sensation of spinning
  • severe sunburn
  • weakness

For Healthcare Professionals

Applies to hydrochlorothiazide: compounding powder, oral capsule, oral solution, oral tablet

Metabolic

Metabolic side effects are common, especially when doses greater than 50 mg per day are used. Mild hypokalemia (decrease of 0.5 mEq/L) occurs in up to 50% of patients, and may predispose patients to cardiac arrhythmias. Metabolic alkalosis, hyponatremia, hypomagnesemia, hypercalcemia, hyperglycemia, and elevated serum uric acid levels are also relatively common. Metabolic problems associated with thiazide diuretics also includes glucose intolerance and a potentially deleterious effect on the lipid profile (i.e., increased serum cholesterol).

Since HCTZ may increase total serum cholesterol by 11%, LDL lipoprotein cholesterol by 12%, and VLDL lipoprotein cholesterol levels by 50%, and may reduce insulin secretion, it should be used with caution in diabetic patients and in those with hypercholesterolemia. True glucose intolerance may develop in approximately 3% of patients. It is typically reversible within six months after discontinuation of therapy.

In contrast, a 3 year study involving healthy older men and women (n=320; 60 to 79 years of age; primarily Caucasian), low dose (12.5 to 25 mg/day) hydrochlorothiazide had minimal effects on lipid metabolism (i.e., triglycerides, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol).

A prospective study of 34 patients who received oral thiazide-type diuretics for 14 years without interruption revealed an increased average fasting blood glucose level after treatment. Withdrawal of thiazide therapy for 7 months in 10 of the patients resulted in average reductions of 10% in the fasting blood glucose and 25% in the 2-hour glucose tolerance test values. A control group was not reported.

Hyperuricemia may be an important consideration in patients with a history of gout. Hypophosphatemia and low serum magnesium concentrations may occur, but are usually clinically insignificant except in malnourished patients.

Hypersensitivity

Hypersensitivity (usually nausea, vomiting, diarrhea, and rash) has been reported in less than 1% of patients. Rare cases of acute pulmonary edema, interstitial cystitis, and interstitial nephritis, and anaphylaxis have been reported.

There have been approximately 34 known cases of thiazide-induced pulmonary edema, encompassing 52 episodes of pulmonary edema, as of 1991 (per a 1996 review). In some cases, doses as small as 12.5 mg were associated with the development of pulmonary edema. The average time to onset of this adverse reaction is 44 minutes, women carry a relative risk of 9:1, and the average age is 56 years. The mortality rate is 6%. Some experts consider this side effect grossly underreported.

Dermatologic

A 67-year-old woman with hypothyroidism, hypercalcemia, depression, and hypertension developed facial erythema, headaches, tremors, confusion and personality changes associated with a new positive ANA and anti-nRNP, and a skin biopsy consistent with lupus erythematosus while taking hydrochlorothiazide (the active ingredient contained in Microzide) (HCTZ), levothyroxine, and amitriptyline. The eruption resolved upon discontinuation of HCTZ, but she later developed a higher ANA titer associated with symptomatic diffuse interstitial pulmonary infiltrates. She was successfully treated with corticosteroids.

Dermatologic reactions include case reports of erythema annular centrifugum, acute eczematous dermatitis, and morbilliform and leukocytoclastic vasculitis. Thiazides may induce phototoxic dermatitis. In addition, a rare, distinct entity with clinical and laboratory features indistinguishable from those of subacute cutaneous lupus erythematosus is associated with HCTZ.

Renal

Although hydrochlorothiazide (the active ingredient contained in Microzide) has been used to treat nephrogenic diabetes insipidus, a case report in which the drug was believed to have caused this condition has been reported.

Renal insufficiency, manifest as an increase in serum creatinine and BUN may occur due to HCTZ-induced intravascular volume depletion. Rare cases of interstitial nephritis have been reported.

Cardiovascular

Cardiac arrhythmias, including ventricular ectopy and complete AV heart block, are associated with hypokalemia and hyponatremia due to HCTZ. Hypotension has been reported in association with HCTZ-induced pulmonary edema. Orthostatic hypotension may occur and may rarely be associated with syncope, particularly in the elderly.

The incidence of premature ventricular contractions as measured by 48-hour ambulatory ECG monitoring is the same in both patients with and without left ventricular hypertrophy despite a similar fall in serum potassium concentrations.

Gastrointestinal

Thiazide diuretics may increase serum cholesterol and triglycerides, resulting in increased risk of cholesterol gallstone formation. Reports of bowel strictures associated with thiazide ingestion have been reported in the 1960's although these patients were on a combination HCTZ-potassium product.

Gastrointestinal side effects are unusual, and include case reports of pancreatitis, nausea, and acute cholecystitis.

Respiratory

Although rare, nearly 40 cases of hydrochlorothiazide-induced noncardiogenic pulmonary edema have been reported including at least two fatalities. Onset of symptoms can occur within minutes (range 10 to 150 minutes) of first exposure to the drug. Associated symptoms include dyspnea, hypoxia, respiratory distress, wheezing, cough, tachypnea, dizziness, nausea, vomiting, diarrhea, and hypotension. Ninety percent of cases have occurred in women at a mean dose of 38.7 mg. Treatment varies, but following discontinuation of hydrochlorothiazide (the active ingredient contained in Microzide) most patients respond, with symptoms resolving in a mean 3.5 days. Rechallenge can result in a more severe reaction, even months to years after the initial exposure. Rechallenge with any thiazide diuretic is not recommended.

Respiratory side effects are rare, and include approximately 40 case reports of acute noncardiogenic pulmonary edema. These cases are thought to be due to idiosyncrasy or a hypersensitivity mechanism.

Immunologic

There are rare case reports of hydrochlorothiazide-induced immune hemolytic anemia. The following illustrates a fatal case:

A 53-year-old man with hypertension developed nausea, vomiting, diarrhea, and progressive anorexia and weakness associated with scleral icterus, anemia with spherocytosis, dark red urine with proteinuria, bilirubinuria, hemoglobinuria, and elevated lactic dehydrogenase levels 18 months after beginning hydrochlorothiazide (the active ingredient contained in Microzide) and methyldopa. Haptoglobin was less than 50 mg per dl. Direct and indirect Coombs tests were positive. The patient died suddenly; autopsy revealed no obvious cause of death, left ventricular hypertrophy, and mild coronary atherosclerosis.

Immunologic side effects are rare, and include case reports of allergic vasculitis and hemolytic anemia. There are numerous case reports of patients developing a rash histologically identical to subacute cutaneous lupus following HCTZ administration.

Hematologic

Hematologic side effects are rare. Cases of immune-complex hemolytic anemia, aplastic anemia, and thrombocytopenia have been reported.

Musculoskeletal

Musculoskeletal side effects are unusual, and include case reports of myalgias and chills. Preservation of mineral bone density has also been observed in older patients.

Nervous system

Nervous system side effects including cerebrovascular insufficiency have been associated with HCTZ-induced plasma volume contraction. At least one case of cognitive and neurologic impairment (i.e., confusion, somnolence, feeling dazed) has been reported. Symptoms immediately resolved following discontinuation of hydrochlorothiazide (the active ingredient contained in Microzide)

Endocrine

Endocrinologic side effects associated with thiazide diuretics include a single case of recurrent parathyroid adenoma, although the association is probably coincidental.

Ocular

Ocular side effects have included idiosyncratic reactions to hydrochlorothiazide (the active ingredient contained in Microzide) resulting in acute transient myopia and acute angle-closure glaucoma.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. Drugs.com does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.

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