Introduction to Pharmacology (Pharmacology and Administration of Medications) (Nursing) Part 2

MEDICATION PREPARATIONS AND ACTIONS

Medications are available for many different purposes and may be administered in various ways. The route of administration refers to the route or method by which a medication is administered.Examples of medication preparations include oral (administered by mouth), topical (applied to the skin or mucous membranes), inhalable (inhaled or breathed in), injectable (given via a needle), and transdermal (applied to and absorbed through the skin).

Medication Names

The number of medications available, as well as the variety of names often given to the same medication, can be confusing. Medications are named in four categories: chemical, generic, official, and trade or brand name. The chemical name describes the medication’s chemical composition. The generic name is often similar to the chemical name and is assigned by the medication’s first manufacturer. The generic name may be simpler than the chemical name and may be used in any country by any manufacturer. The official name is the name identified in the USP or NF or in Canada’s Health Canada’s publications. The trade name or brand name is the copyrighted name assigned by the company manufacturing the medication and is usually followed by the symbol ®. If more than one company makes the same medication, it will have the same generic name, but different trade names. For this reason, many physicians order medications using only the generic name. Box 61-2 gives examples of various names for one medication.


BOX 61-2.

Medication Names

The following is an example of the different names used for one medication.

♦ Chemical formula: C9H8O4

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♦    Chemical name: 2-acetoxybenzenecarboxylic acid

♦    Generic name: acetylsalicylic acid (ASA)

♦    Official name: acetylsalicylic acid

♦    Selected brand names: Aspirin, Aspergum, Bayer, Ecotrin, Heartline, St Joseph. (Also many combination products.)

Many medication labels and inserts list both the generic and trade names. Should the physician use one form of the name and the label states another, verify the names in a designated reference to make sure that the correct medication will be given. If unsure, refer to one of the previously listed drug references before administering any medication to the client. These references commonly list generic and one or more trade names for most medications.

Medication Actions

A medication that produces a desired response is called an agonist. A medication that has an opposing effect, or acts against another medication, is called an antagonist. A medication that enhances the effects of another medication has a synergistic or potentiating effect. The actions of synergistic medications taken together are greater than if either medication were taken separately; the effects are multiplied. Smaller doses of each medication should be used because their combined effects are greater than normal. There may also be interactions between drugs, some of which are dangerous.

Side Effects and Adverse Responses to Medications

Be aware not only of the desired actions of various medications, but also of undesired or secondary reactions. It is important for nurses to be alert constantly for adverse reactions and unwanted side effects of drugs in the client, so appropriate actions can be taken.

Side effects are secondary effects that are other than the initial desired goal of the medication. Some side effects are considered to be adverse or negative reactions and can even be life threatening. However, side effects sometimes can be positive or helpful (Box 61-3).

Key Concept Be aware that in drug reference topics all secondary or side effects, whether negative or positive, are listed as "adverse effects.”

Interactions of Prescription Medications with Herbal Supplements and Homeopathic Remedies

It is important to ask clients if they take dietary supplements, herbs, or homeopathic remedies. Record in the clinical record the type and amount of herb or remedy taken and call it to the attention of the primary care provider.

BOX 61-3. Example of Side Effects/ Adverse Reactions

Medication: diphenhydramine (Benadryl)

♦    Desired effect: Antihistamine; relief of itching and allergy symptoms

♦    Negative, but usually not life-threatening, side effects: Dry mouth, hypotension

♦    Positive, helpful side effects: Cough suppression, relief of motion sickness

♦    Mixed side effects: Sedation that could lead to problems with driving or operating machinery; also helpful as a sleep aid or sedative

♦    Life-threatening adverse effects: Anaphylaxis

Nursing Alert The primary care provider may not be aware that the client takes supplements of herbs or homeopathic remedies. Herbs and homeopathic remedies may have potential drug interactions with a prescribed medication. The supplement may potentially increase or decrease the desired effect of the medication or treatment. Combinations of herbal supplements or of supplements and prescribed medications may also produce life-threatening adverse effects.

Medication Forms

A medication’s form, properties, and desired effects determine its dosage and method of administration. Medications are available in several forms. These forms include liquids, solids, semisolids, metered-dose inhalants, and transdermal medications. Many medications are available in more than one form for different administration routes. For example, promethazine (Phenergan), an antiemetic, is available in rectal suppository, liquid (syrup), and injectable forms. The medication nitroglycerin, which is used to relax vascular smooth muscle (primarily to relieve or prevent angina), is available in many forms, including intravenous (IV) injection, sublingual tablets, sustained-release oral tablets, topical paste, transdermal patches, translingual spray, and transmucosal tablets.

Liquids

Liquids are administered orally, parenterally (by some means other than the gastrointestinal (GI) tract), or topically. Oral Administration of Liquids. Oral administration of liquid medications is used most often for pediatric, psychiatric, and geriatric clients. Oral liquid medications, usually in syrup form, are given to ensure medication compliance, as well as to assist a client who has difficulty swallowing a tablet. Some liquid medications are mixed with juice or another substance to mask the taste. A syrup is a liquid that contains a sweetener, usually sugar. A tincture is a form of a liquid medication that contains alcohol.

Some liquids are designed to be held under the tongue and absorbed through the oral mucosa. Atropine, the liquid medication used to treat enuresis, is administered sublingually and homeopathic remedies are often given in this way. Other liquids are designed to be gargled for their therapeutic effect, such as a warm saline (salt water) gargle for a sore throat. Some are swished in the mouth and then expectorated. An example of a “swish and spit” mouthwash is viscous lidocaine. Another type of medicated mouthwash is designed to be gargled or held in the mouth as long as possible and then swallowed (“swish and swallow” mouthwash). An example of such a mouthwash is nystatin. Medications such as nystatin can also be prepared in other forms, such as frozen flavored ice pops, to assist in compliance. Another form of many medications, including nystatin, is the oral troche, which is a medicated tablet that dissolves in the mouth.

Solid oral medications come in many forms. (Left to right, top) Tablets, caplets, and enteric-coated tablets. (Bottom) Capsules, gel-caps, chewable tablets, and troche.

FIGURE 61-3 · Solid oral medications come in many forms. (Left to right, top) Tablets, caplets, and enteric-coated tablets. (Bottom) Capsules, gel-caps, chewable tablets, and troche.

Topical Administration of Liquids. Liquids for topical use include instillations (as into the eye or ear) and irrigations (as in flushing out a wound).

Solids

Solid medications are those given by mouth. In addition to liquid oral medications, medications given by mouth may be in the form of pills, tablets, capsules, caplets, liqui-gel capsules, gel, or chewing gum (Fig. 61-3). Typically, tablets can be chewed or swallowed (unless they are enteric-coated, in which case, they should be swallowed whole). Some solid or semisolid medications are designed to be placed under the tongue (sublingual) or on the tongue (translingual). An example of translingual administration is the orally disintegrating tablet [ODT]. Another route for medication administration is transmucosal. In this case, a tablet or gel is placed between the cheek and gum and is absorbed through the oral mucosa. An example is glucose in gel form, administered to the client with a dangerously low blood sugar level. When medications are absorbed via the oral mucosa or skin, they bypass the GI tract. Capsules or tablets may contain medications that are absorbed slowly or rapidly (discussed below).

Technically, a pill is absolutely round. However, tablets, capsules, and caplets are commonly referred to as “pills,” even though they are of different compositions and shapes. A tablet is a compressed, spherical form of a medication; tablets may be enteric-coated (the coating does not dissolve until the tablet reaches the intestine, because the medication can irritate the stomach mucosa), or they may be plain. A capsule is a medication in powdered or pellet form enclosed in soluble, cylindrical, gelatin-like material. The capsule may be used to delay the medication’s absorption over time or because the medication has a disagreeable taste. The capsule’s covering also makes swallowing easier than a tablet, which may dissolve in the client’s mouth if he or she does not swallow it quickly. A caplet is a tablet in the shape of a capsule. This shape makes it easier for the client to swallow. A liqui-gel is a liquid-filled capsule that can provide faster absorption than a tablet. Medications in the forms of tablets, capsules, or caplets may be made to release over time (slow release [SR], delayed release [DR], or extended release [ER, XR]) or may be immediate release [IR], designed to release all at one time.

Orally Disintegrating Tablets (ODT). The orally disintegrating tablet is solid, but dissolves very quickly when exposed to saliva in the client’s mouth. These tablets are designed to improve medication compliance, particularly in psychiatric clients or very small children. The ODT form of a drug often has its own trade name. For example, the ODT olanzapine (Zyprexa)—Zyprexa Zydis; of clozapine (Clozaril)—is FazaClo; of risperidone (Risperdal)—is Risperdal M-TAB; and of loratadine is Claritin ODT. Special techniques are used to administer these tablets.

Powders. A powder is another type of solid. Powders are most often mixed with liquids or soft foods for oral administration. They may also be applied topically, inhaled, or combined with a sterile diluent for injection.

Chewing Gum. Chewing gum is used as a medium for delivery of some oral medications. Examples include aspirin (Aspergum) and nicotine (Nicorette gum, used to deliver fixed doses of nicotine for smoking cessation).

Nursing Alert Many tablets and pills can be crushed for easier swallowing or to make sure the client takes them. However not all medications can be crushed safely Capsules, time-released medications, orally disintegrating tablets, and enteric-coated tablets should not be crushed or split. Many facilities require a physician’s order to crush any medication.

Semisolids

Semisolid medications are usually given by rectal, vaginal, or urethral routes. Systemic medication may also be administered by topical paste applied to the skin or a gel given orally. (Other semisolid creams are intended for topical application and are not absorbed systemically.)

Semisolid medications (e.g., a suppository), used for systemic purposes, are designed to melt at body temperature and are absorbed through mucosa or skin. Suppositories usually are kept refrigerated, to maintain their shape. Other semisolid drugs include ointments and pastes. An example of a systemic medication administered by topical paste is nitroglycerin (Nitro-Bid). The dosage of Nitro-Bid is written in measurements of length, such as “1 inch.” (Fig. 61-4).

Nitro-Bid is available in a paste and is ordered in inches.

FIGURE 61-4 · Nitro-Bid is available in a paste and is ordered in inches.

Inhaled Medications and Nasal Sprays

Oral or nasal inhalers and nebulizers deliver medications topically to the area of desired effect (e.g., lung or nasal mucosa). Inhalers are either an aerosol (metered-dose inhaler [MDI]) or a nonaerosol powder inhaler (Turbuhaler, Diskus). They deliver a measured amount of medication with each inhalation. A nebulizer is a device that delivers liquid medication to the airways in the form of a mist as the client inhales. Each dose typically can take as long as 5 minutes to nebulize. The advantage of this type of delivery is that the inhaled drug provides a topical administration to the lung tissue and reduces the systemic side-effects on the body, such as rapid heart rate, or other uncomfortable reactions. These considerations are especially important when using steroids or sympathomimetics.

Other inhaled medications are intended to cause systemic effects. An example is nicotine for inhalation (Nicotrol Inhaler), used to assist in smoking cessation. A medication called D.H.E. 45 is a form of ergotamine and it is available as a nasal spray to treat migraine headaches. DDAVP, a form of desmopressin in a nasal spray, is used to treat enuresis. A new inhaled form of insulin, called Exubera, will allow many persons with diabetes to avoid injections.

Transdermal Medications

Transdermal (TD) medications are those designed to be absorbed through the skin (“trans” = through; “dermal” = skin) into the body. This type of medication is incorporated into a resin and prepared in the form of a patch or paste. The patch is placed on the body, and the skin absorbs the medication in controlled amounts over time. Medications that the GI system would destroy can be given effectively via the transdermal route. In addition, the patches are convenient to use. In most cases, transdermal medications require smaller doses than oral medications to achieve the same desired effects. Examples of medications supplied in transdermal patch include fentanyl (Duragesic, Sublimaze), nicotine patches (Nicoderm), nitroglycerin patches, and estrogen patches (Vivelle Dot). As mentioned, Nitro-Bid is a paste applied to the skin and absorbed transdermally.

Injectable Medications

Injectable medications are given by needle into tissues or a blood vessel or by a catheter into a blood vessel. Injectable medications may be given within the layers of the skin (intradermal), under the skin into the subcutaneous tissue layer (subcutaneous), into the muscle tissue (intramuscular [IM]), into the blood vessels (intravenous [IV] or intra-arterial [IA]), or into the area surrounding the spinal cord (intrathecal). The latter is a highly invasive method and is used only when absolutely necessary.

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