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Amlodipine: General Precaution: Since the vasodilation induced by amlodipine is gradual in onset, acute hypotension has rarely been reported after oral use. However, as with any other peripheral vasodilator, caution should be exercised when administering amlodipine, particularly in patients with severe aortic stenosis.
Increased Angina and/or Myocardial Infarction: Rarely, patients particularly those with severe obstructive coronary disease, have developed documented increased frequency, duration and/or severity of angina or acute myocardial infarction on starting calcium channel blocker therapy or at the time of dosage increase. The mechanism of this effect has not been elucidated.
Use in Patients with Heart Failure: In general, calcium channel blockers should be used with caution in patients with heart failure. In a controlled trial on amlodipine in patients with New York Heart Association III and IV heart failure of nonischemic etiology, amlodipine was associated with increased reports of pulmonary edema despite no significant difference in the incidence of worsening heart failure.
Beta-Blocker Withdrawal: Amlodipine is not a β-blocker and therefore, gives no protection against the dangers of abrupt β-blocker withdrawal; any such withdrawal should be by gradual reduction of the dose of β-blocker.
Patients with Hepatic Failure: Use with caution in patients with hepatic disease. The amlodipine plasma elimination t½ is prolonged (56 hrs) in patients with hepatic disease and dosage adjustment is recommended.
Hydrochlorothiazide: Hypotension and Fluid/Electrolyte Imbalance: As with all antihypertensive therapy, symptomatic hypotension may occur in some patients. Patients should be observed for clinical signs of fluid or electrolyte imbalance (eg, volume depletion, hyponatremia, hypochloremic alkalosis, hypomagnesemia, or hypokalemia) which may occur particularly during intercurrent diarrhea or vomiting. Serum electrolytes should be monitored regularly.
Signs and symptoms of fluid and electrolyte imbalance include dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, confusion, seizures, muscle pains or cramps, muscular fatigue, hypotension, oliguria, tachycardia, and gastrointestinal disturbances including nausea and vomiting.
Hypokalemia may develop, particularly with brisk diuresis, when liver cirrhosis is present, or after prolonged therapy. Interference with adequate oral electrolyte intake will also contribute to hypokalemia. Hypokalemia may cause cardiac arrhythmia and may also sensitize or exaggerate the response of the heart to the toxic effects of digitalis (eg, increased ventricular irritability).
Although any chloride deficit is generally mild and usually does not require specific treatment, except under extraordinary situations (eg, liver or renal disease), chloride replacement may be required in the treatment of metabolic alkalosis.
Dilutional hyponatremia may be seen in edematous patients in hot weather. Appropriate treatment is water restriction rather than administration of salt, except in rare instances when the hyponatremia is life-threatening. Appropriate replacement therapy is the treatment of choice in actual salt depletion.
Renal Disease: Use with caution in patients with severe renal disease because thiazides may precipitate azotemia.
Hepatic Disease: Use with caution in patients with hepatic disease or progressive liver disease since minor alterations of fluid and electrolyte balance may precipitate hepatic coma.
Hypersensitivity Reaction: Hypersensitivity reactions to HCTZ may occur in patients with or without a history of allergy or bronchial asthma, but are more likely in patients with such a history. As a sulfonamide derivative, HCTZ can cause skin rashes and blood dyscrasias.
Systemic Lupus Erythematosus: Exacerbation or activation of systemic lupus erythematosus has been associated with the use of thiazide diuretics.
Metabolic and Endocrine Effects: Thiazide therapy may impair glucose tolerance. Dosage adjustment of antidiabetic agents, including insulin, may be required.
Thiazides may decrease urinary calcium excretion and may cause intermittent and slight elevation of serum calcium. Marked hypercalcemia may be evidence of hidden hyperparathyroidism. Discontinue thiazides before taking parathyroid function test.
Thiazide diuretic therapy may increase cholesterol and triglyceride levels.
Hyperuricemia may occur or acute gout may be precipitated in certain patients taking thiazide therapy.
Thiazides have been reported to increase the urinary excretion of magnesium. This may result in hypomagnesemia.
Use in children: Safety and effectiveness in children have not been established.
Use in the elderly: Amlodipine Besilate: Observe caution in amlodipine dose selection for an elderly. Elderly patients are more likely to experience a delayed clearance of amlodipine and can be at greater risk for toxicity.
Hydrochlorothiazide: Thiazide diuretics are more likely to cause hypovolemia, leading to orthostatic hypotension, and reduced glomerular filtration rate can occur. Elderly patients are also more prone to diuretic-induced hypokalemia due to poor dietary intake of potassium.
