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Enduron Side Effects

Generic Name: methyclothiazide

Note: This page contains information about the side effects of methyclothiazide. Some of the dosage forms included on this document may not apply to the brand name Enduron.

For the Consumer

Applies to methyclothiazide: oral tablet

In addition to its needed effects, some unwanted effects may be caused by methyclothiazide (the active ingredient contained in Enduron). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking methyclothiazide:

Incidence not known
  • Abdominal or stomach pain
  • back, leg, or stomach pains
  • black, tarry stools
  • bleeding gums
  • blistering, peeling, or loosening of skin
  • bloating
  • blood in 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 swallowing
  • dizziness, faintness, or lightheadedness when getting up from 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 hands or feet
  • pain in joints or muscles
  • painful or difficult urination
  • pains in stomach, side, or abdomen, possibly radiating to the back
  • pale skin
  • pinpoint red spots on 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 lips or in mouth
  • sores, welting or blisters
  • sugar in the urine
  • swelling of face, fingers, legs, ankles, feet, or lower legs
  • swollen or painful glands
  • tenderness of salivary glands
  • thickening of bronchial secretions
  • tightness in 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 legs
  • weight gain
  • wheezing
  • yellow eyes or skin

Some of the side effects that can occur with methyclothiazide may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

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, thinning of hair
  • inability to have or keep an erection
  • increased sensitivity of skin to sunlight
  • loss in sexual ability, desire, drive, or performance
  • muscle spasm
  • pinpoint red or purple spots on skin
  • redness or other discoloration of skin
  • restlessness
  • sensation of spinning
  • severe sunburn
  • weakness

For Healthcare Professionals

Applies to methyclothiazide: compounding powder, oral tablet


Metabolic changes associated with methyclothiazide (the active ingredient contained in Enduron) as with other thiazide diuretics, are relatively common, especially when daily doses greater than 5 mg are used. Mild hypokalemia (decrease of 0.5 mEq/L) occurs in up to 50% of treated patients. Hypokalemia may predispose patients to cardiac arrhythmias. Metabolic alkalosis, hyponatremia, hypomagnesemia, hypophosphatemia, hypercalcemia, hyperglycemia, hypercholesterolemia, and hyperuricemia are also relatively common. The electrolyte and intravascular fluid shifts that may occur during methyclothiazide diuresis can provoke hepatic encephalopathy or coma in patients with hepatic cirrhosis.[Ref]

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.[Ref]


Cardiovascular complications of diuretic therapy include orthostatic hypotension secondary to intravascular volume depletion. This has resulted in syncope and, in some patients with glaucoma, temporary loss of vision. Rare cases of cerebrovascular accident associated with thiazide-induced diuresis have been reported.[Ref]

Orthostatic hypotension associated with methyclothiazide may be potentiated by concomitant use of alcohol, barbiturates, or narcotics.[Ref]


Thiazides may induce allergic reactions in patients who are allergic to sulfonamides.[Ref]

Hypersensitivity reactions usually involve the skin (cutaneous vasculitis, urticaria, rash, purpura), but may involve the gastrointestinal system (nausea, vomiting, or diarrhea), the genitourinary system (interstitial nephritis), and the respiratory system (acute noncardiogenic pulmonary edema, pneumonitis). Thiazide diuretics may induce phototoxic dermatitis.[Ref]


Dermatologic reactions may indicate hypersensitivity to the drug. Erythema multiforme, Stevens-Johnson syndrome, exfoliative dermatitis (including toxic epidermal necrolysis), and alopecia have been reported in rare cases.[Ref]


A retrospective case-controlled drug surveillance study has revealed the relative risk of acute cholecystitis associated with the use of a thiazide diuretic is 2.0. The suspected explanation for this association is the potentially deleterious effect thiazides have on the serum lipid profile. Methyclothiazide-induced hypercholesterolemia or hypertriglyceridemia may enhance the formation of some types of gallstones.[Ref]

Gastrointestinal problems include diarrhea, vomiting, constipation, or abdominal pain in approximately 5% of patients. Thiazide diuretics have been associated with acute cholecystitis and rare cases of pancreatitis, sialadenitis, and anorexia.[Ref]


Renal side effects including new or worsened renal insufficiency associated with methyclothiazide (the active ingredient contained in Enduron) therapy is a probable sign of intravascular volume depletion and serves as a signal to reduce or withhold therapy. Rare cases of allergic interstitial nephritis have been associated with some thiazide diuretics.[Ref]


Endocrinologic changes associated with methyclothiazide (the active ingredient contained in Enduron) as with other thiazide diuretic agents, include decreased glucose tolerance and a potentially deleterious effect on the lipid profile. This may be important in patients with, or who are at risk for, diabetes or coronary artery disease.[Ref]


Hematologic side effects are rare. Rare cases of immune-complex hemolytic anemia, aplastic anemia, leukopenia, and thrombocytopenia have been associated with methyclothiazide (the active ingredient contained in Enduron) or other thiazide diuretics.[Ref]

Nervous system

Nervous system side effects include vertigo, paresthesias, and restlessness.[Ref]


Musculoskeletal cramping or spasms are occasionally reported during thiazide diuresis.[Ref]


Genitourinary problems are limited to rare complaints of impotence among male patients.[Ref]


1. Black HR, Chrysant SG, Curry CL, Frishman WH, Grimm RH, Lasseter KC, Okun R, Pool JL, Raizada V, Vlachakis ND, et al "Antihypertensive and metabolic effects of concomitant administration of terazosin and methyclothiazide for the treatment of essential hypertension." J Clin Pharmacol 32 (1992): 351-9

2. Pickkers P, Schachter M, Hughes AD, Feher MD, Sever PS "Thiazide-induced hyperglycaemia: a role for calcium-activated potassium channels?" Diabetologia 39 (1996): 861-4

3. Seller, Fuchs M, Podolsky S "The clinical pharmacology of methyclothiazide." Geriatrics Sept (1962): 577-82

4. Kennedy CC, Spiekerman RE, Elveback L "Antihypertensive properties of cryptenamine used with reserpine and methyclothiazide." J Pharm Sci 60 (1971): 1139-41

5. "Product Information. Enduron (methyclothiazide)." Abbott Pharmaceutical, Abbott Park, IL.

6. Bryant JM, Schwartz N, Fletcher L, et al. "Clinical studies of the antihypertensive effects of a new benzothiadiazine diuretic." Curr Ther Res Clin Exp 3 (1961): 1-4

7. Luther RR, Glassman HN, Estep CB, Maurath CJ, Jordan DC "The effects of terazosin and methyclothiazide on blood pressure and serum lipids." Am Heart J 117 (1989): 842-7

8. Labeeuw M, Pozet N, Aissa AH, Zech PY, Sassard J, Laville M "Uric acid renal handling: spontaneous changes and influence of a thiazide alone or associated with triamterene." Int J Clin Pharmacol Ther Toxicol 26 (1988): 79-83

9. Soghikian K, Bartenbach DE "Influence of dosage and duration of therapy on the rate of response to methyclothiazide in essential hypertension." South Med J 70 (1977): 1397-404

10. Mackay EV, Khoo SK "Clinical and laboratory study of a new diuretic agent ("vectren") in pregnancy: a comparison with a diuretic agent in current use ("enduron")." Med J Aust 1 (1969): 607-12

Not all side effects for Enduron may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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. 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.