Drug information of Methyclothiazide


Methyclothiazide systemic is used in the treatment of:

  • Edema
  • High Blood Pressure

Mechanism of effect

The diuretic and saluretic effects of Methyclothiazide result from a drug-induced inhibition of renal tubular reabsorption of electrolytes. The excretion of sodium and chloride is greatly enhanced. Potassium excretion is also enhanced to a variable degree, as it is with the other thiazides. Although urinary excretion of bicarbonate is increased slightly, there is usually no significant change in urinary pH. Methyclothiazide has a per mg natriuretic activity approximately 100 times that of the prototype thiazide, chlorothiazide. At maximal therapeutic dosages, all thiazides are approximately equal in their diuretic/natriuretic effects.

Like other benzothiadiazines, Methyclothiazide also has antihypertensive properties, and may be used for this purpose either alone or to enhance the antihypertensive action of other drugs. The mechanism by which the benzothiadiazines, including Methyclothiazide, produce a reduction of elevated blood pressure is not known. However, sodium depletion appears to be involved. 


There is significant natriuresis and diuresis within 2 hours after administration of a single-dose of Methyclothiazide. These effects reach a peak in about 6 hours and persist for 24 hours following oral administration of a single-dose.

Methyclothiazide is rapidly absorbed and slowly eliminated by the kidneys as intact drug but primarily as an inactive metabolite. Additional information on the pharmacokinetics is not known at this time

Drug indications

  • Edema
  • High Blood Pressure


Methyclothiazide tablets are administered orally. Therapy should be individualized according to patient response. This therapy should be titrated to gain maximal therapeutic response as well as the minimal dose possible to maintain that therapeutic response.

For edematous conditions

The usual adult dose ranges from 2.5 mg to 10 mg once daily. Maximum effective single-dose is 10 mg; larger single doses do not accomplish greater diuresis, and are not recommended.

For the treatment of hypertension

The usual adult dose ranges from 2.5 mg to 5 mg once daily.

If control of blood pressure is not satisfactory after 8 to 12 weeks of therapy with 5 mg once daily, another antihypertensive drug should be added. Increasing the dosage of Methyclothiazide tablets will usually not result in further lowering of blood pressure.

Methyclothiazide tablets may be either employed alone for mild to moderate hypertension or concurrently with other antihypertensive drugs in the management of more severe forms of hypertension. Combined therapy may provide adequate control of hypertension with lower dosage of the component drugs and fewer or less severe side effects

Drug contraindications

Methyclothiazide tablets are contraindicated in patients with anuria and in patients with a history of hypersensitivity to this compound or other sulfonamide-derived drugs.

Side effects

Adverse reactions are usually reversible upon reduction of dosage or discontinuation of Methyclothiazide tablets. Whenever adverse reactions are moderate or severe, it may be necessary to discontinue the drug.

Body as a Whole: Headache, cramping, weakness.

Cardiovascular System: Orthostatic hypotension (may be potentiated by alcohol, barbiturates, or narcotics).

Digestive System: Pancreatitis, jaundice (intrahepatic cholestatic), sialadenitis, vomiting, diarrhea, nausea, gastric irritation, constipation, anorexia.

Hemic and Lymphatic System: Aplastic anemia, hemolytic anemia, agranulocytosis, leukopenia, thrombocytopenia.

Hypersensitivity Reactions: Anaphylactic reactions, necrotizing angiitis (vasculitis, cutaneous vasculitis), Stevens-Johnson Syndrome, respiratory distress including pneumonitis and pulmonary edema, fever, purpura, urticaria, rash, photosensitivity.

Most  checked interactions

  • Adderall XR (amphetamine / dextroamphetamine)
  • Augmentin (amoxicillin / clavulanate)
  • Calciferol (ergocalciferol)
  • Chewable Calcium with Vitamin D (calcium / vitamin d)
  • Claritin (loratadine)
  • Co-trimoxazole (sulfamethoxazole / trimethoprim)
  • Crestor (rosuvastatin)
  • Demerol (meperidine)
  • Dextrose (glucose)
  • Diovan (valsartan)
  • L Thyroxine Roche (levothyroxine)
  • Lasix (furosemide)
  • Metoprolol Succinate ER (metoprolol)
  • Nasacort Allergy 24HR (triamcinolone nasal)
  • Paracetamol (acetaminophen)
  • Seromycin (cycloserine)
  • Spiriva (tiotropium)
  • VESIcare (solifenacin)


Methyclothiazide shares with other thiazides the propensity to deplete potassium reserves to an unpredictable degree.

Thiazides should be used with caution in patients with renal disease or significant impairment of renal function, since azotemia may be precipitated and cumulative drug effects may occur.

Thiazides should be used with caution in patients with impaired hepatic function or progressive liver disease, since minor alterations of fluid and electrolyte balance may precipitate hepatic coma.

Pregnancy level


Breast feeding warning

Thiazides are excreted in breast milk. Because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug taking into account the importance of the drug to the mother.

Related drugs

Amlodipine , Spironolactone , Furosemide , Losartan , Lisinopril , Metoprolol , Hydrochlorothiazide , Bumetanide , Chlorthalidone


Drug forms

Aquatensen, Enduron

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