Side Effects of Thalitone (chlorthalidone)

Thalitone (chlorthalidone) is a thiazide diuretic used in the treatment of high blood pressure, congestive heart failure, and edema (fluid retention). The brand name Thalitone is discontinued in the U.S. 

Common side effects of Thalitone include

• dizziness,
• lightheadedness,
• headache,
• fatigue,
• nausea,
• vomiting,
• abdominal pain, and
• constipation.

Serious side effects of Thalitone include

• low blood levels of potassium, sodium, and magnesium due to increased excretion via urine;
• high blood calcium levels, especially in persons who are taking calcium supplements;
• increased levels of uric acid in the blood (but gout rarely occurs), and
• high blood sugars in patients with diabetes.

Drug interactions of Thalitone include loop diuretics such as furosemide, bumetanide, and torsemide, because Thalitone can lower blood potassium and magnesium levels because both potassium and magnesium are lost in the urine.

• Low potassium and magnesium levels can lead to abnormal heart rhythms, especially in patients taking digoxin. Thalitone reduces the kidney's ability to eliminate lithium in the urine. As a result, patients taking Thalitone at the same time as drugs containing lithium may develop high levels of lithium and lithium toxicity.
• Nonsteroidal anti-inflammatory drugs (NSAIDs) can reduce the effectiveness of Thalitone though the reason for this is not clear.
• Blood sugar levels can be elevated by thiazide diuretics. Patients with diabetes may need to adjust the doses of medications they are taking for treating diabetes.

Thiazide diuretics including Thalitone cross the placenta and can cause jaundice in the fetus or newborn. Thalitone should not be used during pregnancy unless absolutely necessary. 

Large doses of thiazide diuretics may suppress milk production, but the American Academy of Pediatrics considers thiazides to be compatible with breastfeeding. 

Chlorthalidone generally is well tolerated.

Side effects include:

• dizziness,
• lightheadedness,
• headache,
• fatigue,
• nausea,
• vomiting,
• abdominal pain, and
• constipation.

More serious side effects include:

• Low blood levels of potassium, sodium, and magnesium due to increased excretion via urine.
• High blood calcium levels also can occur, especially in persons who are taking calcium supplements.
• Thiazide diuretics such as chlorthalidone increase the levels of uric acid in the blood, but gout (which is caused by high levels of uric acid) rarely occurs.
• Chlorthalidone can cause high blood sugars in patients with diabetes.

The following adverse reactions have been observed, but there is not enough systematic collection of data to support an estimate of their frequency.

• Gastrointestinal System Reactions: anorexia, gastric irritation, nausea, vomiting, cramping, diarrhea, constipation, jaundice (intrahepatic cholestatic jaundice), pancreatitis.
• Central Nervous System Reactions: dizziness, vertigo, paresthesias, headache, xanthopsia.
• Hematologic Reactions: leukopenia,agranulocytosis,thrombocytopenia, aplastic anemia.
• Dermatologic-Hypersensitivity Reactions: purpura, photosensitivity, rash, urticaria, necrotizing angiitis (vasculitis) (cutaneous vasculitis), Lyell's syndrome (toxic epidermal necrolysis).
• Cardiovascular Reaction: Orthostatic hypotension may occur and may be aggravated by alcohol,barbiturates or narcotics.
• Other Adverse Reactions: hyperglycemia, glycosuria, hyperuricemia, muscle spasm,weakness,restlessness,impotence.

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

• Chlorthalidone may add to or potentiate the action of other antihypertensive drugs.
• Insulin requirements in diabetic patients may be increased, decreased or unchanged. Higher dosage of oral hypoglycemic agents may be required.
• Chlorthalidone and related drugs may increase the responsiveness to tubocurarine.
• Chlorthalidone and related drugs may decrease arterial responsiveness to norepinephrine. This diminution is not sufficient to preclude effectiveness of the pressor agent for therapeutic use.
• Lithium renal clearance is reduced by chlorthalidone,increasing the risk of lithium toxicity.

Drug/Laboratory Test Interactions

• Chlorthalidone and related drugs may decrease serum PBI levels without signs of thyroid disturbance.