Module 2: Drugs for HTN Flashcards
Diuretics
- Thiazide diuretics
These medications increase urine output by acting on the kidneys to reduce the amount of sodium and water reabsorbed into the blood. This action reduces the volume of fluid flowing through your blood vessels, which lowers blood pressure.
**Hydrochlorothiazide and chlorthalidone - Loop diuretics
These are more potent diuretics that work at the loop of Henle in the kidney. They prevent the reabsorption of sodium and chloride, leading to increased urine production.
**Furosemide (Lasix) - Potassium-sparing diuretics
These diuretics help the body get rid of excess sodium and water while keeping potassium levels from getting too low. They work by either blocking the actions of aldosterone or directly affecting sodium channels in the kidney.
**Spironolactone and eplerenone are examples that block aldosterone, while amiloride and triamterene act on sodium channels
Direct-acting vasodilators: Hydralazine and minoxidil
They work by directly relaxing the muscles in the walls of blood vessels, particularly arteries, which leads to their dilation (widening). This widening of the blood vessels helps to lower blood pressure.
**Hydralazine
-specifically acts on the arteries (not veins) causing them to relax and widen. This reduces the resistance the heart has to pump against, thereby lowering blood pressure
-often used in combination with other antihypertensive medications, particularly when blood pressure is difficult to control. It’s also a choice for pregnant women with hypertension
**Minoxidil
-Minoxidil is a more potent vasodilator than hydralazine and works by opening potassium channels in smooth muscle cells of blood vessels, leading to vasodilation
-generally reserved for more severe cases of hypertension or when hypertension is resistant to other treatments. Minoxidil is often used in combination with a diuretic and a beta-blocker to prevent fluid retention and tachycardia, respectively.
Calcium channel blockers
Work by affecting the way calcium is used in the blood vessels and the heart, which helps to relax and widen blood vessels, making it easier for the heart to pump blood and thus lowering blood pressure
How They Work:
**Calcium is crucial for the contraction of muscle cells, including those in the heart and blood vessels. **Calcium channel blockers prevent calcium from entering the cells of the heart and blood vessel walls.
-This action leads to the relaxation (dilation) of blood vessels, which reduces the resistance the heart must pump against, thereby lowering blood pressure.
Types of Calcium Channel Blockers:
**There are two main types: dihydropyridine and non-dihydropyridine calcium channel blockers.
-Dihydropyridines: Such as amlodipine, nifedipine, and felodipine, primarily act on the blood vessels. They are more likely to cause vasodilation and are commonly used for hypertension.
-Non-Dihydropyridines: Such as verapamil and diltiazem, affect both the heart and blood vessels.
They can slow the heart rate as well as dilate blood vessels and are used for treating hypertension, angina, and certain heart rhythm disorders.
Drugs that suppress RAAS
ACE inhibitors
-These drugs block the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. By doing so, they cause blood vessels to relax and dilate, lowering blood pressure.
-Common ACE inhibitors include lisinopril, enalapril, and ramipril.
-They are generally beneficial for people with diabetes as they can help protect kidney function, which can be compromised in diabetic patients.
Angiotensin II receptor blockers
ARBs block the action of angiotensin II at its receptor site. Like ACE inhibitors, they lead to vasodilation and reduced blood pressure.
Examples include losartan, valsartan, and olmesartan.
ARBs are often used in patients who cannot tolerate ACE inhibitors due to side effects like cough.
Aldosterone antagonists
hese drugs block the effects of aldosterone, a hormone that increases sodium and water retention, which can raise blood pressure.
Spironolactone and eplerenone are examples of aldosterone antagonists.
They are particularly useful in heart failure but can also be used in hypertension, especially in resistant cases.
Direct renin inhibitors: Type 2 diabetes mellitus precautions
Direct renin inhibitors, such as aliskiren, work by directly inhibiting renin, an enzyme that initiates the RAAS cascade.
They are a newer class of drugs and can be used in patients for whom other RAAS inhibitors are not suitable.
Type 2 Diabetes Mellitus Precautions:
While RAAS inhibitors can offer kidney protection in diabetic patients, there are important considerations:
These drugs can increase potassium levels, which need to be monitored, especially in patients with kidney impairment.
There is a risk of low blood pressure (hypotension), especially in the initial stages of therapy.
It’s essential to monitor kidney function regularly, as these drugs can affect renal function.
HTN Fundamentals for Drug Therapy
Treatment Algorithm:
The algorithm typically starts with lifestyle modifications (like diet and exercise) and progresses to include medications, depending on the severity and control of blood pressure.
Initial Drug Selection:
Patients WITHOUT Compelling Indications: For these patients, initial medication typically includes thiazide diuretics, ACE inhibitors, angiotensin II receptor blockers (ARBs), calcium channel blockers, or in some cases, beta-blockers.
Patients WITH Compelling Indications: For patients with specific conditions like diabetes, heart disease, kidney disease, or a history of stroke, the choice of medication may be different. For example, ACE inhibitors or ARBs are often preferred in patients with diabetes due to their kidney-protective effects.
Adding Drugs to the Regimen:
Rationale for Drug Selection: Additional drugs are chosen based on their ability to effectively lower blood pressure and their suitability for the patient’s overall health profile.
Benefits of Multidrug Therapy: Often, a combination of drugs is more effective than a single medication. Different classes of drugs work in various ways to lower blood pressure, and their combined effect can be synergistic.
Dosing:
The dosing of hypertension medications is often started at a low dose and gradually increased as needed to achieve optimal blood pressure control, while minimizing side effects.
Step-Down Therapy:
If blood pressure is well-controlled for a significant period, the doctor might reduce the dosage or the number of medications. This must be done cautiously to ensure that blood pressure remains within a safe range.
Fundamentals for Treating HTN
Patients with Comorbid Conditions:
Renal Disease: Patients with kidney disease often benefit from drugs that protect kidney function, such as ACE inhibitors or angiotensin II receptor blockers (ARBs). However, these patients require careful monitoring for kidney function and electrolyte levels.
Diabetes: For diabetic patients, controlling blood pressure is critical to prevent complications. ACE inhibitors or ARBs are often chosen for their protective effects on the kidneys, a common concern in diabetes. Calcium channel blockers and diuretics are also effective and commonly used
Patients in Special Populations:
African Americans: This group often responds better to certain types of medications, like calcium channel blockers and diuretics, compared to ACE inhibitors or ARBs alone. They may also require higher doses or a combination of medications to achieve optimal blood pressure control.
Children and Adolescents: Treatment in this group typically starts with lifestyle changes, and if medication is necessary, dosing and choice of drug are carefully considered based on age, size, and underlying health conditions.
Older Adults: Blood pressure management in older adults must be balanced with the risk of side effects, as they may be more sensitive to certain medications. Lower initial doses and gradual titration may be necessary. Medications like diuretics and calcium channel blockers are often effective, but careful monitoring is essential to avoid complications like electrolyte imbalances or renal dysfunction.
Drugs for Hypertensive
Emergencies
Sodium Nitroprusside:
This is a potent vasodilator that acts quickly, making it ideal for emergency situations. It works by relaxing blood vessels, which lowers blood pressure.
It’s administered intravenously and its effects can be seen almost immediately.
Because it’s so potent, it requires close monitoring in a hospital setting.
Fenoldopam:
Fenoldopam is a vasodilator that works by dilating peripheral arteries.
It’s particularly useful in patients with kidney issues as it can enhance kidney perfusion.
Like sodium nitroprusside, it’s administered intravenously and requires monitoring.
Labetalol:
Labetalol is a beta-blocker with some alpha-blocking activity, meaning it relaxes blood vessels and slows the heart rate.
It’s often used in hypertensive emergencies due to its efficacy and relatively good safety profile.
It can be given intravenously or orally, but in emergencies, the IV form is used for rapid effect.
Diazoxide:
Diazoxide is a fast-acting vasodilator. It’s particularly effective in lowering blood pressure quickly.
However, it can cause significant fluctuations in blood glucose levels, so it must be used with caution, especially in diabetic patients.
Clevidipine:
Clevidipine is a calcium channel blocker that is used intravenously.
It works by relaxing the blood vessels and is effective in quickly reducing blood pressure.
Its effects are rapid and easily controllable, making it a useful option in acute settings.
