Antihypertensives Flashcards
What is hypertension (primary vs secondary)?
BP > 140/90 mmHg
Primary hypertension: idiopathic, >90%
Secondary hypertension: specific causes like renal artery stenosis, adrenaline-producing adrenal tumour, <10%
What are the complications of hypertension?
Congestive heart failure
MI
Ischemic heart disease
Renal damage
Stroke
What are the 4 main categories of 1st line antihypertensives?
Diuretics
Beta-blockers
ACE inhibitors
Calcium channel blockers
What are the subcategories of diuretics?
Thiazides
Loop diuretics
Loop diuretics are more potent, often given as acute diuretics for patients for acute cardiac failure/emergencies but not for chronic usage as antihypertensives
What happens at the nephron DCT?
Impermeable to water
Na+Cl- cotransporter reabsorbs NaCl, diluting tubular fluid
Ca2+ is actively reabsorbed
What are thiazides?
The most widely used diuretic agents
E.g. hydrochlorothiazide
Inhibits NaCl cotransporter and thus reduces NaCl reabsorption in the PCT
Enhances Ca reabsorption in the DCT
Enhances urea reabsorption and inhibits urea excretion (exacerbates gout)
Dependent on PG synthesis, so NSAIDs reduce thiazide action
What are thiazides used for?
Hypertension
Congestive heart failure
What are the adverse effects of thiazides?
Hypokalemia
Hyponatremia
Hyperglycemia
Hyperlipidemia
Hyperuricemia
Hypercalcemia
What are two important beta-blockers?
Propranolol (non-selective)
Atenolol (beta-1 selective)
What does beta 1 receptor activation in the heart do?
Stimulates increased cAMP
Induces increased heart contractility and speed
Beta blockers therefore reduce rate and force and BP
What are the clinical uses of beta blockers?
Hypertension
Angina
Following MI
What are the adverse effects of beta blockers?
Bradycardia
Bronchospasm
Sedation
Vivid dreams
What are the contraindications for beta-blockers?
Asthma, COPD
Bradycardia
Reflex tachycardia
History of hypoglycemia/diabetes (beta blockers mask symptoms of hypoglycemia such as sweating, increased HR, tremors and dizziness)
What is the function of ACE?
Converts Ang I to Ang II, where Ang II stimulates vasoconstriction and aldosterone release to increase BP
What are some ACE inhibitors?
Captopril, enalapril, lisinopril
How do ACE inhibitors work?
Prevent conversion of Ang I to Ang II, preventing Ang II-induced vasoconstriction, aldosterone release, and BP increase
Inhibits breakdown of bradykinin, causing vasodilation to decrease BP
Too much bradykinin causes cough, may have to switch medication
What are the clinical uses of ACE inhibitors?
Hypertension
Cardiac failure
Following MI
What are the adverse effects of ACE inhibitors?
Severe hypotension
Hyperkalemia
Angioedema
Dry cough due to accumulation of bradykinin
Acute renal failure
Contraindicated in pregnancy
What are 3 calcium channel blockers?
Verapamil, diltiazem, nifedipine
Why are calcium channel blockers more used than antihypertensives?
They are also anti-angina and anti-arrhythmia, similar to beta blockers
They reduce the hyperactivity of the SA node
Verapamil/diltiazem vs Nifedipine?
Verapamil and diltiazem reduce overactivity of the SA and AV nodes to treat arrhythmia
Nifedipine reduces myocardial contractility and smooth muscle tone to treat angina and hypertension
Why is it important to step up dosages for calcium channel blockers?
If BP drops very quickly you may get stroke/hypotension
What are the side effects of lowering calcium concentrations?
Vasodilation, leading to flushing, headache, reflex tachycardia due to compensation for decreased blood pressure
What are the adverse effects of calcium channel blockers?
Constipation
Headache
Tachycardia
Severe hypotension
Dizziness
Flushing
What antihypertensive should you not prescribe to a patient with gout?
Thiazides
What antihypertensive should you not prescribe to a patient with diabetes?
Beta-blockers
