Thiazide & thiazide-like diuretics Flashcards
MoA
Inhibits Na+/Cl- transported in distal convoluted tubule.
Prevents reabsorption of sodium and its osmotically associated water.
Indications
- Alternative 1st line treatment where CCB would be used either unsuitable or there are features of HF.
- Resistant hypertension (BP that isn’t adequately controlled by a CCB + ACEi/ARB)
Thiazide diuretics
Bendroflumethiazide
Chlorothiazide
Hydrochlorothiazide
Thiazide-like diuretics
Indapamide
Chlortalidone
Metolazone
Xipamide
How long do they take to work?
1-2 hour onset
12-24 hour duration
Side effects
GI disturbances
Impotence
High LDL/triglycerides
Hyperglycaemia/diabetes
Gout (more common than loop diuretics)
Hyponatraemia
Hypokalaemia = Cardiac arrhythmias
Hypochloraemia
Hypomagnesaemia
Metabolic alkalosis (hypercalcaemia)
Thiazides + eGFR
Ineffective if eGFR <30 ml/min EXCEPT Metolazone
Hypertension
Indapamide (2.5 mg OD)
Chlortalidone (12.5 - 25 mg OD)
Recommended options for hypertension.
Bendroflumethiazide 2.5 mg OD is commonly used but not recommended (little evidence to support its use)
Little benefit from increase dose - increases SE without significantly improving antihypertensive effect.
Bendroflumethiazide
HF = 5 mg OM
Hypertension = 2.5 mg OM
Indapamide
Less likely to cause diabetes
Metolazone
Use in severe renal failure
Chlortalidone
Long half-life - give on alternate days if acute retention is a problem/dislikes frequent urination
Interactions
NSAIDs - reduce diuretic effect. Low dose aspirin is okay.
Other drugs that lower serum potassium/cause hypokalaemia.
Monitoring
BP control
Measure serum electrolytes before treatemnt, 2-4 weeks after starting treatment and after any change in therapy.
Develop acute illness e.g. become sick = risk of dehydration
Hydrochlorthiazide
Associated with risk of melanoma and skin cancer, particularly in long-term use.
Patients should be advised to limit exposure to sunlight and UV rays.
