ORAL AND ENTERAL PREPARATIONS WITH CLINICAL APPLICATIONS

Objectives

• State the advantages and disadvantages of administering oral medications.

• Calculate oral dosages from tablets, capsules, and liquids using given formulas.

• Give the rationale for diluting and not diluting oral liquid medications.

• Explain the method for administering sublingual medication.

• Calculate the amount of drug to be given per day in divided doses.

• Determine the amount of tube feeding solution needed for dilution according to the percent ordered.

• Determine the amount of water needed to dilute liquid medication.

Oral administration of drugs is considered a convenient and economical method of giving medications. Oral drugs are available as tablets, capsules, powders, and liquids. Oral medications are referred to as po (per os, or by mouth) drugs and are absorbed by the gastrointestinal tract, mainly from the small intestine.

There are some disadvantages in administering oral medications, such as (1) variation in absorption rate caused by gastric and intestinal pH and food consumption within the gastrointestinal tract; (2) irritation of the gastric mucosa causing nausea, vomiting, or ulceration (e.g., with oral potassium chloride); (3) retention or inactivation of the drug in the body because of reduced liver function; (4) destruction of drugs by digestive enzymes; (5) aspiration of drugs into the lungs by seriously ill or confused patients; and (6) discoloration of tooth enamel (e.g., with a saturated solution of potassium iodide [SSKI]). Oral administration is an effective way to give medications in many instances, and at times it is the route of choice.

Body weight and body surface area are discussed in Chapter 7. When solving drug problems that require body weight or body surface area, refer to Chapter 7.

Enteral nutrition and enteral medication are discussed toward the end of the chapter. Calculations of percent for enteral feeding solutions and enteral medication are also discussed.

TABLETS AND CAPSULES

Most tablets are scored and can be broken in halves and sometimes in quarters (Figure 8-1). Half of a tablet may be indicated when the drug does not come in a lesser strength. Half-tablets may not be broken equally; therefore, the patient may receive less than or more than the required dose. Also, crushing a drug tablet does not ensure that the patient will receive the entire drug dose. Some of the crushed tablet could be lost. Instead of halving or crushing a drug tablet, use the liquid form of the drug, if available, to ensure proper drug dosage. If a tablet or pill is not scored, then it should NOT be broken or altered.

Figure 8-1 A and B, Shapes of tablets. C and D, Shapes of capsules. (From Kee, J. L., Hayes, E. R., & McCuistion, L. E. [2012]. *Pharmacology: A nursing process approach,* 7th ed. Philadelphia: Saunders.)

Capsules are gelatin shells containing powder or time pellets. Caplets (solid-looking capsules) are hard-shell capsules. Time-release capsules should remain intact and not be divided in any way. Many drugs that come in capsules also come in liquid form. When a smaller dose is indicated and is not available in tablet or capsule form, the liquid form of the drug is used (Figure 8-2).

Figure 8-2 Medicine cup for liquid measurement. (From Kee, J. L., Hayes, E. R., & McCuistion, L. E. [2012]. *Pharmacology: A nursing process approach,* 7th ed. Philadelphia: Saunders.)

Pill/Tablet Cutter

A pill or tablet cutter can be used to evenly split or divide a scored or unscored tablet. The pill cutter cannot be used to cut/divide enteric-coated tablets or capsules, time-released, sustained-released, or controlled-released capsules. Pill/tablet cutters can be purchased at a drug store (Figure 8-3).

CAUTION

• Instead of breaking or crushing a tablet, use the liquid form if available.

• Time-released, sustained-released, or controlled-released capsules should not be crushed or diluted because the entire medication could be absorbed rapidly.

• Enteric-coated tablets must NOT be crushed because the medication could irritate the stomach. Enteric-coated tablets are absorbed by the small intestine.

• Tablets or capsules that are irritating to the gastric mucosa should be taken with 6 to 8 ounces of fluid, with meals or immediately after meals.

Calculation of Tablets and Capsules

The following steps should be taken to determine the drug dose:

1. Check the drug order.

2. Determine the drug available (generic name, brand name, and dosage per drug form).

3. Set up the method for drug calculation (basic formula, ratio and proportion, fraction equation, or dimensional analysis).

4. Convert to like units of measurement within the same system before solving the problem. Use the unit of measure on the drug container to calculate the drug dose.

5. Solve for the unknown (X).

Decide which of the methods of calculation you wish to use, and then use that same method for calculating all dosages. In the following examples, the basic formula, the ratio and proportion, fraction equation, and dimensional analysis methods are used (see Chapter 6).

Basic Formula (BF)

D (desired dose)H (on–hand dose)×V=(vehicle)

Ratio and Proportion (RP

Fraction Equation (FE)

H (on hand)V (Vehicle)(Cross multiply)=D (desired dose)X (unknown)

Dimensional Analysis (DA)

V=V×C(H)×DH×C(H)×1

Note: C = conversion factor if needed.

EXAMPLES

PROBLEM 1: Order: pravastatin sodium (Pravachol) 20 mg, daily.

Drug available:

Methods:

BF:DH×V

2010×1=2 tablets

RP: H : V :: D : X

10 mg:1 tab::20 mg:X tab

10 X = 20

X = 2 tablets

FE:HV=DX=(Cross multiply)101=20X=10X=20 X=2 tablets

DA: no conversion factor

ANSWER: Pravachol 20 mg = 2 tablets, daily.

PROBLEM 2: Order: erythromycin (ERY-TAB) 0.5 g, qid (four times a day).

Drug available:

Note: Grams (g) and milligrams (mg) are units in the metric system. Remember: When changing grams (larger unit) to milligrams (smaller unit), move the decimal point three spaces to the right. Refer to Chapter 1, Table 1-2. Because the drug dose on the drug label is in milligrams, conversion should be from grams to milligrams.

Methods: 0.5 g = mg or 500 mg

BF:DH×V=500250×1=500250=2 tablets

RP: H : V :: D : X

250 mg:1 tab::500 mg:X tab

250X=500X=2 tablets

FE:2501=500X(Cross multiply) 250X=500 X=2 tablets

ANSWER: ERY-TAB 0.5 g = 2 tablets

PROBLEM 3: Order: aspirin 650 mg, po, STAT.

Drug available: aspirin 325 mg per tablet.

Methods:

BF:DH×V=650mg325mg×1=21=2 tablets

RP: H : V :: D : X

325 mg:1 tab::650 mg:X tab

325X=650X=2 tablets

FE:HV=DX=(Cross multiply)3251=650X=325X=650 X=2 tablets

ANSWER: Aspirin 650 mg = 2 tablets.

LIQUIDS

Liquid medications come as tinctures, elixirs, suspensions, and syrups. Some liquid medications are irritating to the gastric mucosa and must be well diluted before being given (e.g., potassium chloride [KCl]). Usually, liquid cough medicines are not diluted. Medications in tincture form are always diluted or should be diluted.

Liquids are designed to be taken orally or through an enteral tube and are made palatable by the addition of sweeteners such as suctrose, aspartame, saccharin, fructose, and sorbital. Unpalatable liquid drugs can be mixed with 30 to 60 mL of fruit juice.

CAUTION

• Concentrated liquid medication that can irritate the gastric mucosa should be diluted in at least 6 ounces of fluid, preferably 8 ounces of fluid.

• Liquid medication that can discolor the teeth should be well diluted and taken through a drinking straw.

Calculation of Liquid Medications

EXAMPLES

PROBLEM 1: Order: potassium chloride (KCl) 20 mEq, po, bid.

Drug available: liquid potassium chloride 10 mEq per 5 mL.

Methods:

BF:DH×V=2010×5=10010=10mL

RP: H : V :: D : X

10 mEq:5 mL::20 mEq:X mL

10X = 100

X = 10mL

DA: no conversion factor

ANSWER: Potassium chloride 20 mEq = 10 mL

PROBLEM 2: Order: amoxicillin (Amoxil) 0.25 g, po, tid.

Drug available:

Change grams to milligrams: 0.25 g = mg or 250 mg

Methods:

BF:DH×V=250125×5=1250125=10mL

RP: H : V :: D : X

125 mg:5 mL::250 mg:X mL

125 X = 1250

X = 10 mL

FE:HV×DX=1255×250X=(Cross multiply) 125X=1250 X=10mL

ANSWER: Amoxil 0.25 g = 10 mL

PROBLEM 3: Give SSKI 300 mg, q6h, diluted in water.

Drug available: saturated solution of potassium iodide, 50 mg per drop (gt), drops (gtt).

Methods:

BF:DH×V=30050×1=30050=6gtt

RP: H : V :: D : X

50 mg:1 gt::300 mg:X gtt

50X = 300

X = 6gtt

ANSWER: SSKI 300 mg = 6 gtt (drops)

BUCCAL TABLETS

Buccal tablets are dissolved when held between the cheek and gum, permitting direct absorption of the active ingredient through the oral mucosa. The buccal tablet should be placed in the buccal cavity, above the rear molar between the upper cheek and gum.

CAUTION

The patient should not split, crush, or chew the tablet.

EXAMPLE

PROBLEM 1: Order: fentanyl buccal tablet, 100 mcg, STAT.

Available: 4 fentanyl, 100-mcg tablet each in a blister package. Dissolve 1 tablet in the buccal cavity over 30 minutes; then swallow the remaining pieces.

SUBLINGUAL TABLETS

Few drugs are administered sublingually (tablet placed under the tongue). Sublingual tablets are small and soluble and are quickly absorbed by the numerous capillaries on the underside of the tongue. Sublingual tablet may be called “orally disintegrating” tablet. Today some sublingual administration may include steroids, enzymes, and cardiovascular drugs.