Introduction

The cardiovascular system deals with the heart and blood vessels. Different types of drugs are used to treat conditions related to the heart and blood based on the issue that the patient is experiencing. Respiratory conditions and kidney disorders are also treated in this way.

Drugs Used in the Cardiovascular System

A variety of subclassifications apply to drugs that act on the heart and blood vessels.

Antiarrhythmic drugs are given to correct variations from normal heart rhythms. Some work as beta blockers, that is, blocking the action of epinephrine that may be overexciting the heart and blood vessels. Others are calcium-channel blockers, which block the entrance of calcium into cells.

Antihypertensive drugs fight high blood pressure. High blood pressure is often called the "silent killer" because there are often no symptoms to recognize that the blood pressure is higher than it should be. But if it's detected and brought under control, the person with hypertension can live a long and healthy life.

There are many classes of medications used to treat high blood pressure. First-line treatment options usually include diuretics, angiotensin-converting enzyme inhibitors (ACE-I), angiotensin II receptor blockers (ARB), or calcium-channel blockers. Diuretics are antihypertensives because they cause the kidneys to excrete more urine, resulting in a lower volume of blood in the body and therefore less pressure on the blood vessels.

Other classes of drugs to treat high blood pressure include vasodilators and beta blockers. Vasodilators act as antihypertensives by widening blood vessel walls, which makes it easier for blood to pass through without excessive pressure. Medications that work in the cardiovascular system may have more than one indication for use. For example, vasodilators, beta blockers, and calcium-channel blockers may be effective for angina. Beta blockers and calcium-channel blockers act as antihypertensives as well as antiarrhythmics.

Vasoconstrictors narrow the blood vessels and raise blood pressure. Obviously, this wouldn't be desirable in most people suffering from cardiovascular diseases. But it's sometimes necessary to get blood moving during cardiac or respiratory failure. Atherosclerosis, a condition where plaque builds up in the arteries, is a factor in many cardiovascular diseases. Since cholesterol contributes to atherosclerosis, cholesterol-lowering drugs are important, too.

Anticoagulants may be used to break up clots that form within blood vessels; thus, they're effective for patients with thrombosis or embolism. Anticoagulants can prevent clot formation in susceptible patients and in donated blood that's being stored for transfusions. Heparin is a natural anticoagulant produced by the liver and white blood cells. Coagulant may be given if a patient receives an overdose of anticoagulant or has a clotting deficiency.

Antihypertensives Used in Treatment

High blood pressure, or hypertension, affects millions of people in the United States. No one knows what causes most forms of high blood pressure. If left untreated, however, high blood pressure leads to additional diseases such as stroke, renal failure, blindness, and heart failure.

It's imperative to return high blood pressure to a normal level. Blood pressure can sometimes be lowered through weight loss, exercise, and reduction of salt intake. Often, however, antihypertensive drugs must be used.

Antihypertensive drugs work in several ways to lower high blood pressure, depending on the mechanism of action of the medication. If the arteries are constricted, causing the pressure inside them to rise, drugs may be used that dilate (open up) the arteries, resulting in decreased blood pressure. Drugs that dilate constricted arteries are angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, calcium-channel blockers, and others such as alpha 1 receptor blockers.

Some antihypertensives act on the heart to make it beat more slowly and with less force, reducing the amount of blood volume that's pumped into the arteries. Drugs that act on the heart to reduce blood outflow are called beta-adrenergic blocking agents (beta blockers).

Diuretics cause increased urination, which decrease the volume of fluid in the plasma. Less fluid volume within the arteries usually results in less pressure within the cardiovascular system. These drugs are often combined with antihypertensives to increase the antihypertensive effect.

Angiotensin-converting enzyme (ACE) is normally present in the blood as part of the body's blood pressure regulation system. ACE causes production of a very powerful constricting substance; overproduction contributes to high blood pressure. ACE inhibitors block the actions of this enzyme, causing dilation of the blood vessels and reducing blood pressure.

These drugs have a beneficial effect on the kidneys. The names of ACE inhibitors end in "pril." For example, enalapril, lisinopril, and benazepril are the generic names for three popular ACE inhibitors. One of the more annoying side effects of ACE inhibitors is a dry cough; if this happens, then a patient may be told to stop taking the ACE-I and to take an ARB (angiotensin II receptor blocker) instead.

Related to ACE inhibitors are angiotensin II receptor blockers (ARBs). ARBs prevent angiotensin II, a vasoconstrictor, from binding to receptors; this reduces blood pressure. ARBs are less likely to produce the dry cough caused by ACE inhibitors. Popular drugs in this class include Diovan (valsartan), Avapro (irbesartan), and Cozaar (losartan). Notice that the generic names of all of the ARBs end in "-sartan."

Calcium-channel blockers (CCBs) lower blood pressure by dilating constricted blood vessels. The smooth muscle cells that line the arteries use calcium to regulate their contraction.

Calcium passes through channels in the cell membranes when they open in response to certain hormones. When calcium is taken into the cell, it contracts, causing tightening within the blood vessels. CCBs block these channels and therefore the uptake of calcium. The blockage of calcium by CCBs eases this tightening effect and leads to dilated blood vessels and lower blood pressure.

There are two different subclasses of calcium-channel blockers, each one having a different indication. For high blood pressure, CCBs such as nifedipine (Procardia), amlodipine (Norvasc), or felodipine may be prescribed. For other cardiovascular conditions, CCBs such as verapamil or diltiazem may be used. Although these may help lower blood pressure as well, they're not typically used just to treat high blood pressure alone.

Beta-adrenergic receptor blockers decrease the heart's rate and force of contraction. This in turn lowers oxygen use to prevent myocardial ischemia and pain. Beta blockers are often used for the chronic management of angina. The names of beta-adrenergic receptor blockers end in "-olol." Examples are atenolol, metoprolol, carvedilol, and propranolol.

There are other ways to cause dilation of the arteries. Drugs that don't fit into the previous categories are found in the alpha-blocker class of antihypertensives. Two drugs in this category are prazosin (Minipress) and doxazosin (Cardura). They block alpha receptors within the arterioles to cause vasodilation. In addition to reducing blood pressure, some medications in this class may be used to treat benign prostate hypertrophy (BPH).

Cholesterol-Lowering Drugs

Cholesterol-lowering drugs are used to treat hyperlipidemia (high cholesterol) and prevent atherosclerotic risk in patients. Cholesterol is believed to contribute to atherosclerosis, which is related to many heart problems. Thus, these drugs are important for managing heart health.

Statin therapy is considered to be the first-line treatment option to treat high cholesterol and prevent cardiovascular disease in patients. Statins are grouped by their intensity, which is the percentage of LDL-lowering expected from the medication.

High intensity statins that lower LDL by at least 50% include atorvastatin and rosuvastatin. Moderate-intensity statins are lower doses of atorvastatin or rosuvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, and simvastatin. Low-intensity statins include lower doses of flavustatin, lovastatin, simvastatin, pitavastatin, and pravastatin. In addition to statins, there are other medications that lower levels of triglycerides and increase levels of HDL, the good cholesterol.

Types of Heart Medication

Medical conditions associated with the heart also include heart failure, arrhythmia, angina, and myocardial infarction, which is also known as a heart attack. Antiplatelet medications may be used to prevent recurrence of strokes and heart attacks in survivors of these two conditions. Drugs that reverse arrhythmia are called antiarrhythmics, and drugs that prevent angina are called antianginals. The anticoagulant class of heart medicines is often referred to as blood thinners.

Heart failure means that the heart muscle is unable to pump the blood sufficiently to provide body tissues with oxygen. Many of the medication classes that you've learned about also have a place in therapy for heart failure. There are different types of heart failure—it's in the type called heart failure with reduced ejection fraction (HFrEF) that many of these medications have been proven to prolong life, improve the functioning of the heart, and lessen complications related to heart failure. ACE-I, ARBs, and the newest class of medication, called angiotensin-receptor neprilysin inhibitor (ARNI), help improve the way the heart works and reduce deaths related to heart failure.

There's only one drug available at this time in the ARNI class, called sacubitril/valsartan (Entresto). Only one medication from the ACE-I, ARB, or ARNI class should be used at one time because these classes work similarly. Combining medications from these drug classes can be dangerous.

Another new class is the /f channel blocker and there's only one drug available in that class, called ivabradine (Corlanor).

Beta blockers are also used for heart failure. One way they work is by allowing the left ventricle to fill more completely by slowing the heart rate. The three beta blockers that have shown the most benefit for patients with HFrEF are bisoprolol, carvedilol, and metoprolol succinate. Other classes of medications that are prescribed include aldosterone antagonists, which are also potassium-sparing diuretics, and a vasodilator (hydralazine) combined with isosorbide dinitrate. Diuretics are an important treatment for patients with heart failure if they have any edema or fluid buildup in their body including the lower legs, feet, and lungs. Digoxin may also be used in some patients to help with symptoms if the other standard therapies aren't enough to treat the heart failure.

There are many diverse drugs that reverse the disorderly pattern of heartbeats seen in cardiac arrhythmias. Cardiac arrhythmias are disorders of electrical impulse conduction throughout the heart. The beating of the heart is initiated and stimulated by electrical impulses from the sinoatrial node, which is located in the muscle of the right atrium. This node is a natural peacemaker. Electrical impulses ordinarily allow for a smooth pattern of heartbeats. When the electrical conduction becomes disorderly, the normal beating pattern is lost and heart rhythm changes.

The following drugs are commonly used to treat arrhythmias: quinidine, verapamil (Calan), digoxin, propafenone (Rythmol), sotalol (Betapace), acebutolol (Sectral). The many drugs used to manage and correct arrhythmia do so by several different complicated mechanisms. Many of these medications are also associated with side effects and drug interactions.

Angina pectoris, or angina, is characterized by an intense pain in the chest caused by cardiac oxygen deprivation, a lack of oxygen in the heart muscle. The classic symptoms of an angina attack are tightness of the chest, excruciating pain of the chest, shortness of breath, and pain radiating down the left arm. Angina isn't the same as a heart attack. Angina usually occurs because of a blockage in the coronary arteries (ischemia). The diseased arteries can't deliver enough oxygen to meet the heart's demand.

Some angina attacks occur at rest and aren't associated with an increased myocardial demand. The pain associated with this form of angina is believed to be caused by reductions in oxygen supply because of coronary artery spasm and occlusion.

Nitrates such as nitroglycerin dilate the coronary blood vessels to allow for adequate oxygen flow to the heart muscle. Nitroglycerin is the most commonly used drug to treat angina.

It's often prescribed in pill form; the pill is placed under the tongue for rapid effect during an angina attack.

However, when exposed to air and light, nitroglycerin degrades. To solve this problem a spray was developed, which is contained in an airtight cylinder until it's sprayed under the tongue. Nitroglycerin is also prescribed in the form of a skin patch that's worn to prevent angina attacks.

Other nitrates that are prescribed to prevent angina include isosorbide dinitrate and isosorbide mononitrate.

Drugs that treat angina by dilating the coronary blood vessels are bepridil (Vascor) and nifedipine (Procardia), both of which are calcium-channel blockers. Beta-adrenergic receptor blockers, such as propranolol, are also used to treat angina because they decrease the workload of the heart.

Anticoagulants and antiplatelets reduce the blood's ability to clot. They're used to treat conditions such as deep vein thrombosis (DVT), pulmonary embolism (PE), and to prevent stroke in patients with atrial fibrillation. They may also be used short-term in the hospital to prevent clots.

Antiplatelets drugs are used to prevent clotting in the arterial circulation and are typically used to prevent heart attack and stroke in patients who are at high risk.

Warfarin (Coumadin) was one of the first available oral anticoagulant drugs. Warfarin requires rigorous monitoring of patients.

Newer oral options of anticoagulants have become available that don't require the same rigorous monitoring that warfarin does; however, they may not be an appropriate alternative for all patients who require an anticoagulant.

Examples of these newer anticoagulants include: dabigatran (Pradaxa), rivaroxaban (Xarelto), and apixaban (Eliquis). Two of the more common injectable anticoagulants include heparin and Lovenox.

Examples of antiplatelets medications include aspirin, clopidogrel (Plavix), prasugrel (Effient), ticagrelor (Brilinta), and ticlopidine (Ticlid). Cilostazol (Pletal) is a mediction that's used to treat peripheral artery disease.

Types of Kidney Medication

Diuretics are medicines that promote the excretion of sodium, along with large amounts of water, from the kidneys. Medical conditions in which the accumulation of water is harmful are treated with diuretics. These conditions include high blood pressure, congestive heart failure, and edema (swelling due to excess fluid under the skin). Diuretic drugs are categorized according to their mechanisms of excretion: thiazide diuretics, carbonic anhydrase inhibitors, loop diuretics, and potassium-sparing diuretics.

The thiazide diuretics are so called because of the chemical nature of their molecules. They contain a sulfur atom that's identified in chemistry as "thia." Thus, thiazide means "sulfur-containing molecule." The thiazides promote the excretion of sodium ions from the kidneys. Sodium ions in turn carry large amounts of water with them, and volumes of water are effectively released from the body.

Many patients on thiazide diuretics will also be on potassium supplements, since the body tends to excrete potassium along with sodium. Other drugs such as chlorthalidone, though chemically different from thiazides, are similar in action. Thiazides are the most widely used diuretic agents and the drug hydrochlorothiazide (HCTZ) is the most popular thiazide. Other common thiazides include indapamide (Lozol) and metolazone (Zaroxolyn). HCTZ and chlorthalidone are considered to be first-line treatment options for high blood pressure in many patients.

Carbonic anhydrase is an enzyme involved in the normal kidney function of urine formation and water retention. Inhibition of this enzyme results in more water excretion than retention. Thus, diuresis occurs with these drugs.

Acetazolamide (Diamox) is the most common carbonic anhydrase inhibitor. Although these drugs are classified as a type of diuretic, they're more commonly used in the treatment of glauoma.

The nephron is the functional unit of the kidney where urine formation occurs. The portion of the nephron that contains the greatest concentration of urine is called the loop of Henle. Loop diuretics act on this loop to allow for the formation of large amounts of urine. Therefore, large amounts of water are excreted. As with the thiazides, patients on loop diuretics will also likely be on potassium supplementation since potassium gets lost to the urine along with sodium.

Loop diuretics are the most effective diuretics and are used when the passage of large amounts of water is desired. Furosemide (Lasix) is the most popular loop diuretic. Other useful loop diuretics are torsemide (Demadex) and bumetanide (Bumex). Loop diuretics are often the diuretic of choice in patients who have edema because of heart failure.

The previously mentioned diuretics cause not only excretion of sodium and water but also potassium. Loss of potassium is dangerous in some patients, particularly those with heart problems. Many patients who take these diuretics also take extra potassium in the form of supplemental tablets or potassium-rich food such as bananas.

Potassium-sparing diuretics keep potassium within the body so that the patient doesn't need potassium supplements. Potassium-sparing diuretics aren't as effective as thiazides and loop diuretics, but some products, such as triamterene with hydrochlorothiazide (Dyazide), combine potassium-sparing diuretics and thiazides to improve efficacy. Other potassium-sparing diuretics are amiloride (Midamor) and spironolactone (Aldactone).

Types of Respiratory Medications

Respiratory drugs are used primarily to treat, prevent, or relieve conditions in the respiratory system including cold, cough, allergies, asthma, and COPD. One of the reasons allergy symptoms occur is because of a release of histamine.

1. Antihistamines oppose the action of histamine.

2. Antitussives prevent or relieve coughing, usually by acting on the medullary center of the brain to inhibit the cough reflex.

3. Decongestants reduce the swelling of mucous membranes in nasal passages.

4. Expectorants thin mucus secretions, allowing them to drain or be more easily expelled from the system.

A major healthcare problem in the United States is the inappropriate use of antibiotics for respiratory conditions. Many of these diseases are viral in nature, so they don't respond to antibiotics. Only bacterial infections respond to antibiotics. But some clinicians nevertheless prescribe antibiotics. Part of the problem is that medical professionals face great public pressure to prescribe.

When people see a doctor for an illness, they generally want a prescription medication that will cure it. This pressure may influence some doctors to prescribe antibiotics for viral illnesses. The other contributing factor is that some viral infections are difficult to distinguish from bacterial infections.

Antibiotic-Resistant Bacteria

The most serious problem of the overprescribing of antibiotics is that it encourages the emergence of antibiotic-resistant bacteria, which aren't affected by the usual drugs. Infections caused by such antibiotic-resistant bacteria are difficult to eradicate. A person who has been exposed to multiple regimens of antibiotics can easily develop a resistant infection. The most effective method of battling this problem is using antibiotics appropriately. This means that viral illnesses shouldn't be treated with antibiotics. Instead, viral rhinitis, sinusitis, or bronchitis can be treated with other medications, such as decongestants, bronchodilators, and inhaled corticosteroids.

Antihistamines work against histamine, which causes the mucous membranes of the respiratory system to become inflamed and produce fluid, as seen in nasal and seasonal allergies. This effect of histamine results from its action on specific cell sites called histamine "type 1" (H1) receptors. Histamine also causes excess secretion of stomach acid in conditions of gastric hyperacidity or heartburn. This effect of histamine results from its action on specific cell sites in the stomach called histamine "type 2" (H2) receptors.

Antihistamines can block the actions of histamine at either the H1 receptor sites (H1 blockers) or the H2 receptor sites (H2 blockers).

Blocking the H1 receptor sites results in the reduction of allergy symptoms associated with rhinitis. Blocking the H2 receptor sites results in decreased stomach acid production. The H1 blockers are further subdivided into antihistamines that produce sedation and drowsiness as a side effect and those that are nonsedating. Many antihistamines can now be purchased without a prescription.

Bronchodilators open up the airway passages to allow for better air intake in conditions of asthma. Bronchodilators are administered as inhalants, dispensed from pressurized handheld containers, or orally in the form of tablets and liquids.

There are two types of asthma inhalers: metered-dose inhalers (MDIs) and dry-powder inhalers (DPIs). The technique required to use each type of inhaler is different. These drugs are also available in solutions that are delivered via a nebulizer, which is a breathing machine that changes the medication from a liquid to a mist for inhalation.

Asthma is a chronic condition characterized by wheezing, chest tightness, difficulty breathing, and coughing. Asthma is caused by a partial obstruction of the bronchi and bronchioles due to abnormal contraction of the muscles in the bronchial walls. When the bronchi become blocked, the mucous membranes become swollen with fluid. Stale air then becomes trapped, and the amount of new air that can enter the lungs becomes limited, resulting in a characteristic wheezing sound. There's no cure for asthma, but the symptoms can be treated and prevented.

Both adults and children may have asthma—in 2015, it was estimated that about 8.4% of children and 7.6% of adults have asthma in the United States. In people suffering from asthma, a genetic factor may predispose them to be hypersensitive to certain allergens, such as dust, pollens, animal dander, or some foods. Asthma exacerbations, also known as asthma attacks, can stem from infections, certain drugs, vigorous exercise, and stress. An asthma attack is defined as a sudden worsening of asthma symptoms.

Drugs that cause dilation of the bronchi and bronchioles have been found to be effective in reducing the symptoms of asthma. The drugs open the passages to allow for optimal air intake and breathing.

There are two types of bronchodilators—short-acting and long-acting beta2-agonists. The short-acting bronchodilators act quickly to open the bronchi and bronchioles and are used to provide immediate relief of asthma symptoms. Representative inhalants and oral bronchodilators are listed in the following table.

The long-acting bronchodilators are used to prevent asthma symptoms and are most often combined with an inhaled corticosteroid. Less commonly, theophylline is taken orally for the treatment of asthma. For patients with underlying allergies and asthma, drugs such as zafirlukast (Accolate), montelukast (Singulair), and zileuton (Zyflo) may also be used. Representative inhalants and oral bronchodilators are listed in the table.

Medications for Coughs, Colds, and Allergies

The common cold is the most common cause of time lost from work and school, more than any other illness. It's the most prevalent illness in the winter months. The public spends hundreds of millions of dollars on over-the-counter cough and cold preparations each year. Children 1 to 5 years old are the most susceptible to the common cold and may average up to 12 episodes per year. Individuals 25 to 30 years old average about six respiratory illnesses per year.

Viruses cause the common cold. Symptoms include mucus accumulation in the nose and sinuses, profuse watery discharge from the nose (rhinorrhea), sneezing, and fever (usually low-grade). Sneezing is caused by a combination of nasal irritation, discharge, and congestion. It subsides when the secretions clear. There are no curative remedies for the common cold, and medications are intended to provide relief from the symptoms of this ailment.

Antitussives

A cough is usually associated with the common cold. Coughs are classified as productive or nonproductive. A productive cough removes secretions and phlegm from the lower respiratory tract. A nonproductive cough is a dry cough in which secretions or phlegm aren't present. OTC medicines used to stop coughs are called cough suppressants or antitussives.

Cough suppressants are taken when there's a need to stop a persistent cough. The two cough suppressants found in commercial products are codeine and dextromethorphan. Codeine is the most effective antitussive agent, to which all other are compared. Codeine cough medicines are available only by prescription because of their narcotic content.

Dextromethorphan is a non-narcotic anticough medication used in OTC cough medicines. Dextromethorphan affects the cough center in the medulla, increasing the threshold at which we're stimulated to cough, which in turn makes us cough less.

Expectorants

Expectorants act to decrease the viscosity (thickness) of the sputum (saliva and respiratory discharge) in coughing conditions. This action promotes ease of expectoration (the discharge of matter from the throat). The most popular expectorant is guaifenesin. Examples of over-the-counter products that have guaifenesin as an ingredient include Robitussin and Mucinex.

Although not federally mandated, many retailers have restricted the sale of products containing dextromethorphan to persons over the age of 18 because dextromethorphan has become a drug of abuse among the adolescent population. At very high doses, dextromethorphan can cause euphoria and hallucinations. These high doses are very dangerous and can cause death, especially since dextromethorphan is commonly combined with other active ingredients that can also become toxic at high doses.

Decongestants

Another drug class used to treat colds is decongestants. Decongestants are drugs that cause constriction of the blood vessels in the nasal passages. This action results in shrinkage of the swollen vessels and mucous membranes and reduction of nasal discharge. It also promotes drainage and relieves stuffiness. The drugs are delivered either as nasal sprays, tablets, or liquids. People who have high blood pressure should talk to their healthcare provider before taking any form of decongestant because these medications may elevate their blood pressure.

Nasal decongestants are sprayed into the nose to cause constriction of the dilated blood vessels that produce congestion. Intranasal application of decongestants provides prompt relief of nasal congestion. Shrinkage of the mucous membranes not only makes breathing easier but also permits the sinus cavities to drain. These nasal decongestants should be used for a maximum of three days to prevent rebound nasal congestion. The following nasal decongestant agents are used in most commercial products:

Naphazoline (in Privine and others) is a potent vasoconstrictor that has a duration of about six hours.
Phenylephrine (in Neo-Synephrine and others) is commonly applied as two or three drops or as a spray every four hours.
Oxymetazoline and xylometazoline (in Afrin and others) are longer-acting agents having a decongestant effect of five to six hours.

There are two oral decongestants that are swallowed as pills to provide systemic relief of nasal congestion: pseudoephedrine and phenylephrine. In an effort to combat methamphetamine use, the sale of pseudoephedrine is restricted. The Methamphetamine Anti-Proliferation Act requires that sales of pseudoephedrine products be tracked, either electronically or in a written log. In many states, pseudoephedrine products are kept behind the pharmacy counter and customers must present a valid photo ID to buy them. There are also restrictions on the maximum amount of pseudoephedrine that can be sold to one person.

Phenylephrine is available over the counter, without any restrictions for purchase. Although there isn't enough evidence to say one is more effective than the other, some think pseudoephedrine may be more effective. The other difference between pseudoephedrine and phenylephrine is that phenylephrine is available only in a short-acting formulation, so it needs to be taken several times a day, while pseudoephedrine is available in short-acting, 12-hour, and 24-hour formulations.

Mold spores and plant pollens that depend on the wind for cross-pollination are the agents responsible for most seasonal allergies. Ragweed, grass, and tree pollens cause many seasonal allergies. The main symptoms of seasonal allergies are swelling (edema) of the nasal mucosa, sneezing, nasal itching, and nasal congestion.

Antihistamines

Histamine is the causative agent that contributes to cold and allergy symptoms, and antihistamines block the effects of histamine in tissues and reduce these symptoms. Antihistamines act by blocking histamine receptor sites and are most effective in controlling allergic rhinitis. The most common antihistamines found in commercial products are diphenhydramine, phenyltoloxamine, doxylamine, and chlorpheniramine.

First-Generation Antihistamines

First-generation can be considered sedating antihistamines. The first-generation antihistamines are effective at controlling cold and allergy symptoms, but they can cause drowsiness in the patient. These medications may be chosen over second-generation antihistamines due to their effectiveness over certain allergic reactions.

Second-Generation Antihistamines

The second-generation antihistamines have the advantage of not causing drowsiness. Thus, they may be preferred by a patient.

Loratadine (Claritin), fexofenadine (Allegra), and cetirizine (Zyrtec) are second-generation antihistamines that are available over the counter. Levocetirizine (Xyzal) and desloratadine (Clarinex) are other second-generation antihistamines, currently available by prescription only.

Key Points

Antiarrhythmic drugs are given to correct variations from normal heart rhythms.
Beta blockers block the action of epinephrine, which may overexcite the heart and blood vessels. Antihypertensive drugs fight high blood pressure. Vasodilators widen blood vessels, making it easier for blood to pass through.
Diuretics cause the kidneys to excrete more urine, resulting in a lower volume of blood in the body.
Angiotensin-converting enzyme (ACE) is normally part of the body's blood-pressure regulation system, causing production of a powerful constricting substance. ACE inhibitors block the actions of ACE, causing dilation of the blood vessels and reducing blood pressure.
Angiotensin II receptor blockers (ARBs) prevent angiotensin II, a vasoconstrictor, from binding to receptors, reducing blood pressure. Calcium-channel blockers (CCBs) lower blood pressure by dilating constricted blood vessels by blocking the calcium that regulates contraction.
Beta-adrenergic receptor blockers decrease the heart's rate and force of contraction; this lowers oxygen use to prevent myocardial ischemia and pain.
Antiarrhythmics reverse the disorderly pattern of heartbeats seen in cardiac arrhythmias, which are disorders of electrical-impulse conduction through the heart. Antianginals treat angina, an intense pain in the chest caused by a lack of oxygen in the heart muscle. Anticoagulants reduce the blood's ability to clot; clots that form within blood vessels can cause stroke and heart attack.
Diuretics are medicines that promote excretion of sodium and large amounts of water from the kidneys; they're prescribed with potassium supplements since potassium gets lost to urine along with sodium. Diuretics are used to treat high blood pressure, congestive heart failure, and obesity, all conditions in which an accumulation of water is harmful.
Respiratory drugs are used primarily for opening bronchial tubes and reversing the effects of histamines, which cause inflammation of the respiratory system. Antihistamines counteract the action of histamine.
Antitussives prevent or relieve coughing by inhibiting the cough reflex. Decongestants reduce swelling of mucous membranes in nasal passages. Expectorants thin mucous secretions, allowing them to drain or be more easily expelled from the system.

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