Antihypertensive Drugs, Uses, Side Effects, Drug Interactions

Antihypertensive drugs are a class of drugs that are used to treat hypertension (high blood pressure). Antihypertensives drugs therapy seeks to prevent the complications of high blood pressure, such as stroke and myocardial infarction. Evidence suggests that reduction of the blood pressure by 5 mmHg can decrease the risk of stroke by 34%, of ischaemic heart disease by 21%, and reduce the likelihood of dementia, heart failure, and mortality from cardiovascular disease. There are many classes of antihypertensives, which lower blood pressure by different means. Among the most important and most widely used drugs are thiazide diuretics, calcium channel blockers, ACE inhibitors, angiotensin II receptor antagonists (ARBs), and beta blockers.

Includes therapeutic agents that can be used for lowering of blood pressure.

Alpha-Blockers (Antihypertensive)

Alpha blockers, also called alpha-adrenergic antagonists, dilate blood vessels by blocking postsynaptic alpha1-adrenergic receptors. Alpha blockers are generally not recommended as initial therapy.

Alpha-2 Agonists, Central-Acting

Alpha-2 adrenergic receptor agonists work by stimulating alpha-2 receptors and decreasing sympathetic activity, which leads to decreased blood pressure and heart rate.

Aldosterone Antagonists, Selective

Angiotensin II Receptor Blockers

Angiotensin receptor blockers work by blocking the effects of hormone angiotensin II (type 1 receptor). As a result, blood vessels dilate and blood pressure is reduced.

ACE (Angiotensin Converting Enzyme) Inhibitors

ACE inhibitors remain the initial treatment of choice for hypertension. This class of drugs blocks the conversion of angiotensin I to angiotensin II by inhibiting angiotensin-converting enzyme (ACE), thus preventing constriction of blood vessels.

Beta-blockers

Beta-blockers produce antihypertensive action by reducing heart rate and cardiac output. Currently beta-blockers are not recommended as first-line treatment due to the risk of stroke and new-onset of type 2 diabetes when compared to other medications

Calcium Channel Blockers

Calcium channel blockers decrease the entry of calcium into the cells of the heart and blood vessels. By blocking the entry of calcium, this class of drugs reduces heart rate and contractility and dilates arteries.

Diuretics, Loop

Loop diuretics lower blood pressure by reducing blood volume. These medications inhibit the sodium-potassium-chloride cotransporter in the thick ascending limb of the loop of Henle. Loop diuretics promote water loss and increase sodium excretion.

Diuretics, Potassium-Sparing

Potassium-sparing diuretics work by leaving more potassium in the blood, as a result more sodium and water are excreted in the urine. Potassium-sparing diuretics are weak antihypertensives when used alone.

Diuretics, Thiazide

Thiazide diuretics reduce sodium absorption from the distal tubule segment of the kidney. Thiazide diuretics are known to worsen insulin sensitivity and elevate serum total cholesterol levels

Peripheral Adrenergic Inhibitors

These medications are rarely used unless other medications don’t help.

Renin Inhibitors

Renin inhibitors act by inhibiting the activity of renin, the enzyme responsible for angiotensin II levels.

Vasodilators

Vasodilators work by dilating arterioles. However, vasodilatation by itself causes increased sympathetic outflow to the heart, leading to tachycardia and increased contraction.

Antihypertensive Combinations

Blood pressure medications

Telmisartan affects the renin-angiotensin-aldosterone. You shouldn’t take this drug with other medicines that affect this system. These drugs include:

• aliskiren. Telmisartan and aliskiren shouldn’t be used together in adults with diabetes or moderate kidney disease.
• angiotensin receptor blockers (ARBs), such as:
  • candesartan (Atacand, Atacand HCT)
  • eprosartan (Teveten)
  • irbesartan (Avapro, Avalide)
  • losartan (Cozaar, Hyzaar)
  • olmesartan (Benicar, Benicar HCT, Tribenzor, Azor)
  • valsartan (Diovan, Diovan HCT, Exforge, Exforge HCT)
  • azilsartan (Edarbi, Edarbyclor)
• angiotensin-converting enzyme (ACE) inhibitors, such as:
  • benazepril (Lotensin, Lotrel, Lotensin HCT)
  • captopril
  • enalapril (Vasotec, Epaned)
  • fosinopril (Monopril)
  • lisinopril (Prinivil, Zestril, Prinzide, Zestoretic)
  • moexipril (Uniretic)
  • perindopril (Aceon)
  • quinapril (Accupril, Accuretic)
  • ramipril (Altace)
  • trandolapril (Mavik, Tarka)

Mechanism of Action of Antihypertensives Drugs

Antihypertensive drug competes with sympathomimetic neurotransmitters such as catecholamines for binding at beta(1)-adrenergic receptors in the heart, inhibiting sympathetic stimulation. This results in a reduction in resting heart rate, cardiac output, systolic and diastolic blood pressure, and reflex orthostatic hypotension.

Antihypertensive drugs is classified as a non-cardioselective sympatholytic beta blocker that crosses the blood–brain barrier. It is lipid soluble and also has sodium channel blocking effects.  Antihypertensive drugs is a non-selective beta blocker; that is, it blocksthe action of epinephrine (adrenaline) and norepinephrine (noradrenaline) at both β₁– and β₂-adrenergic receptors. It has little intrinsic sympathomimetic activity, but has strong membrane stabilizing activity (only at high blood concentrations, e.g. overdose). Antihypertensive drugs is able to cross the blood–brain barrier and exert effects in the central nervous system in addition to its peripheral activity.

In addition to blockade of adrenergic receptors, Antihypertensive drugs has very weak inhibitory effects on the norepinephrine transporter and/or weakly stimulates norepinephrine release (i.e., the concentration of norepinephrine is increased in the synapse).Since propranolol blocks β-adrenoceptors, the increase in synaptic norepinephrine only results in α-adrenoceptor activation, with the α₁-adrenoceptor being particularly important for effects observed in animal models. Therefore, it can be looked upon as a weak indirect α₁-adrenoceptor agonist in addition to potent β-adrenoceptor antagonist.In addition to its effects on the adrenergic system, there is evidence that indicates that antihypertensive drugs may act as a weak antagonist of certain serotonin receptors, namely the 5-HT_1A, 5-HT_1B, and 5-HT_2Breceptors.The latter may be involved in the effectiveness of propranolol in the treatment of migraine at high doses

or

Antihypertensive drugs competes with sympathomimetic neurotransmitters such as catecholamines for binding at beta(1)-adrenergic receptors in the heart, inhibiting sympathetic stimulation. This results in a reduction in resting heart rate, cardiac output, systolic and diastolic blood pressure, and reflex orthostatic hypotension.

Indications of Antihypertensive drugs

Cardiovascular

• Hypertension
• Angina pectoris (with the exception of variant angina)
• Arrhythmia
• Aortic Stenosis
• Atrial Fibrillation
• Tachyarrhythmia
• Myocardial infarction
• Tachycardia (and other sympathetic nervous system symptoms, such as muscle tremor) associated with various conditions, including anxiety, panic, hyperthyroidism, and lithium therapy
• Portal hypertension, to lower portal vein pressure
• Prevention of esophageal variceal bleeding and ascites
• Anxiety
• Hypertrophic cardiomyopathy
• Hemangioma
• Intermittent Explosive Disorder
• Mitral Valve Prolapse
• Panic Disorder
• Pheochromocytoma
• Portal Hypertension
• Tardive Dyskinesia
• Thyrotoxicosis

Psychiatric

Antihypertensive drugs is occasionally used to treat performance anxiety.Evidence to support its use in other anxiety disorders is poor.Some experimentation has been conducted in other psychiatric areas

• Post-traumatic stress disorder (PTSD) and specific phobias
• Aggressive behavior of patients with brain injuries
• Treating the excessive drinking of fluids in psychogenic polydipsia
• Treatment of specific phobias, such as arachnophobia, dental fear, and social phobia.

Others

• Essential tremor. Evidence for use for akathisia however is insufficient
• Migraine and cluster headache prevention and in primary exertional headache
• Hyperhidrosis (excessive sweating)
• Proliferating infantile hemangioma
• Glaucoma
• Thyrotoxicosis by deiodinase inhibition
• Akathisia caused by antipsychotic use
• Angina Pectoris
• Cardiovascular Mortality
• Gastroesophageal variceal hemorrhage prophylaxis
• Hemangiomas
• High Blood Pressure (Hypertension)
• Idiopathic hypertrophic subaortic stenosis
• Migraines
• Nonvalvular Atrial Fibrillation
• Obstructive Hypertrophic Cardiomyopathy
• Performance Anxiety
• Pheochromocytomas
• Supraventricular Arrhythmias
• Tachyarrhythmia caused by Digitalis intoxication
• Tachyarrhythmia caused by catecholamine excess
• Thyroid Crisis
• Thyrotoxicosis
• Tremor caused by lithium
• Tremor, Essential
• Ventricular Tachycardia

Contra Indications of Antihypertensive drugs

Antihypertensive drugs may be contraindicated in people with

• Reversible airways diseases, particularly asthma or chronic obstructive pulmonary disease (COPD)
• Bradycardia (<60 beats/minute)
• Sick sinus syndrome
• Atrioventricular block (second- or third-degree)
• Shock
• Severe hypotension
• Cocaine toxicity

Side Effects of Antihypertensive drugs

The most common

• Dry cough
• Depression
• Dizziness and light-headedness due to low blood pressure
• Fatigue, especially in the early stages
• Mouth dryness in the early stages
• The most commonrn (a burning feeling in the chest, behind the breastbone or gullet)
• Abdominal or stomach pain
• Constipation
• High blood pressure
• Nausea ,vomiting,
• painful or swollen gums
• numbness or heavy feeling in the jaw
• dull, aching pain in the hip, groin, or thigh
• stomach pain,
• headache,
• reversible hair loss or thinning, and
• fever.

Common

• chills or fever
• headache, severe and throbbing
• joint or back pain
• muscle aching or cramping
• muscle pains or stiffness
• chest pressure or squeezing pain in chest
• excessive sweating
• sudden drowsiness or need to sleep
• coughing up blood
• liver problems–nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes)
• decreased amount of urine

Rare

• Anxiety
• change in vision
• chest pain or tightness
• confusion
• cough
• Agitation
• arm, back, or jaw pain
• blurred vision
• chest pain or discomfort
• convulsions
• extra heartbeats
• hallucinations
• headache
• irritability
• lightheadedness
• cold and clammy skin
• fast and shallow breathing
• swelling of your feet, legs, or hands purple spot on your skin caused by internal bleeding
• fast or abnormal heart rate or palpitations
• loss of appetite
• lower back, side, or stomach pain
• mental depression
• muscle pain or cramps

Drug Interactions of Antihypertensive drugs

Antihypertensive drugs may interact with following drugs, supplyments, & may change the efficacy of drugs

• aminophylline
• asthma medications (e.g., theophylline)
• diabetes medications (e.g., glyburide)
• calcium channel blocker medicines (e.g., diltiazem, nifedipine, verapamil)
• diltiazem
• medications for abnormal heart rhythms (e.g., disopyramide)
• nitroglycerin
• nonsteroidal anti-inflammatory medications (NSAIDs; e.g., indomethacin, naproxen)
• oral diabetes medications (e.g., metformin, pioglitazone)
• pentoxyifylline
• monoamine oxidase (MAO) inhibitors (e.g., phenelzine, selegiline, )
• other beta-blockers (e.g., propranolol, metoprolol)
• oxtriphylline
• verapamil
• SSRI antidepressants including fluoxetine ,paroxetine ,fluvoxamine,
• Other drugs to treat high blood pressure (e.g., clonidine, hydralazine, methyldopa, , haloperidol,)
• other heart medications (e.g. , quinidine),  theophylline, thioridazine, thyroid hormones (e.g., levothyroxine),
• warfarin.

This medication may interfere with certain laboratory tests (including glaucoma screening test, cardiovascular stress testing using arbutamine), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

References

1. https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0025447/
2. https://en.wikipedia.org/wiki/Antihypertensive_drug

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