Antihypertensive medications Flashcards
Which physiological functions might be acted on by the drugs acting on the heart?
1) Rate & Rhythm
2) Myocardial contraction
3) Metabolism and blood flow
- While the drugs acting on the blood vessels affect the vessel tone mainly (vasoconstriction/Vasodilation)
What are the two mechanisms by which heart medications control the heart?
1) Short-term regulation:
- Via the autonomic control of the heart
2) Long-term regulation
- Via the Renin-angiotensins aldosterone system
What are the main adverse effects of the heart drugs?
What are the best antihypertensive medications for specific patients?
1) Patients with asthma
- We give angiotensin-II receptor-blocking (AR-B)
ACE-Inhibitors
2) Patients with kidney failure
- We give Fosinopril
3) Diabetic patients
- Isinopril & hydrochlorothiazide
A-Blockers
4) Pregnant patients
- Labetalol
- Carvedilol
B-BLOCKERS
5) Patients with glaucoma
- Timolol (inhibits the b-2 receptors decreasing the production of aqueous humor)
6) Reduced Renal Function patients
- Nadolol (reduced dose)
- Carteolol (reduced dose)
7) Pheochromocytoma (Tumor in the adrenal gland)
- Labetalol (both an a- and b-blocker)
- Phenobenzamine
- Phentolamine
A-2agonists
8) Renal patients with hypertension
- Clonidine, usually with a diuretic as it causes sodium and water retention
9) Sympatholitcs
- Methyldopa (treats preeclampsia)
How does the CNS control the BP?
1) Resistance arterioles (they are the major vessels that controls the velocity of blood flow, they control them by vasodilating, or constricting them)
2) Capacitance venules (they hold the most amount of blood, CNS can also control their diameter)
3) Heart-pumped output (they can stimulate the B-receptor, controlling the SV, contractility, etc)
4) It can also control the amount of renin released into the system via stimulating the kidneys
What is the most important site where the heart medication should work on?
Resistance arterioles
What is meant by the postural baroreflex?
Drugs acting on the resistance arterioles result in (drop in the BP due to vasodilation “postural baroreflex”) where the reflex vasoconstriction “activating the vasomotor” and the HR will increase in “reflex tachycardia”
- In low BP the kidney activates the RAA system
What is the mechanism of action of the beta blockers?
1) Block the activation of b1 adrenoceptors in the heart decreasing the cardiac output
2) blocking the b2-receptors in the kidney decreasing the release of renin and thus the blood volume
- This drug is an example of a drug that works on two systems autonomic and the kidney
What are the main classes of antihypertensive drugs?
1) Angiotensin-converting enzyme inhibitor (ACEI)
2) Angiotensin-II receptor blocker
3) Antiadrenergics (a-blockers, b-blockers, centrally acting “like clonidine”)
4) Calcium channel blockers
5) Diuretics
6) Direct vasodilators
What are the different drugs acting on the renin-angiotensin-aldosterone system?
1) Angiotensinogen (a2-globulin in blood “produced by the liver”), is converted to angiotensin-I “inactive” via the enzyme Renin and it is inhibited by RENIN INHIBITORS
2) Angiotensin-I is converted to angiotensin-II via the enzyme ACE “angiotensin converting enzyme”, and it is inhibited by ACEI
3) Angiotensin-II will increase the sympathetic output, vasoconstrictor the vascular smooth muscles, and stimulate the secretion of aldosterone, which is inhibited by the ARB’s (Angiotensin-II receptor blocker), which will decrease the BP
4) Aldosterone will stimulate the retention of sodium and water increasing the BP blocking it via an aldosterone receptor antagonist will decrease the BP
What happens if you inhibit the formation of angiotensin 2?
Accumulation of renin
- Thus ACEI causes the accumulation of renin
Can we give ACEI to asthma patients?
- The enzyme ACE converts angiotensin 1 to angiotensin 2 (Vasoconstrictor) and at the same time it converts bradykinin into an inactive metabolite
- If we inhibited the ACE, Bradykinin (vasodilator) will then accumulate which is a good thing but its accumulation will irritate the nerve endings of small nerves, producing an irritant cough (Use Icatibant)
- Angiotensin receptor blockers (ARBs) are away from bradykinin so they’re good substituents in case of asthma
Describe the pharmacokinetics of ACE-Inhibitors
1) Captopril
- Short-acting
2) Enalapril
- Prodrug like all of them is converted via hydrolysis to a converting enzyme inhibitor in the liver (used in diabetic patients)
3) Enalaprilat
- Only IV, for hypertensive emergencies
4) Lysinopril
- Lysine derivative of enalaprilat, the only one which is not a prodrug
5) Fosinopril
- Given to patients with renal failure
7) Others, etc
What are some examples of ACE-inhibitor medications?
1) Captopril (short-acting medication)
2) Enalapril (can be used once or twice daily with better pharmacokinetics)
Describe the pharmacodynamics of the ACE inhibitors
1) Blocks the formation of angiotensin-II: (decreases the peripheral resistance due to the blockage of vasoconstriction)
2) Decreases the release of aldosterone and thus decreases the retention of sodium and water
3) Increases the levels of bradykinin and prostaglandins vasodilating the vessels and thus decreasing the peripheral resistance
- The final result is the vasodilation of the arterioles and venules
Which drug do we describe to a diabetic patient?
Lisinopril & hydrochlrothiazide
What are the side effects of ACE inhibitors?
1) Cough (Usually due to bradykinin)
2) Angioedema (emergency must be treated as it can be fatal)
3) Proteinuria (From captopril, as it contains sulfur causing hypersensitivity)
4) Loss of Taste (Metallic taste)
5) Acute Renal failure
6) Increased Potassium (Hyperkalemia)
7) Fetal anomalies
8) Neutropenia (due to bone marrow suppression)
Which ACE inhibitor is used in case of kidney failure?
Fosinopril
What are the uses of ACE-Inhibitors?
1) Among the first-line treatment of hypertension
2) For chronic congestive heart failure
3) After a myocardial infarction
4) Diabetic nephropathy
Which medication is used to suppress the cough of bradykinin (cyclooxygenase inhibitor)?
Icatibant