Ptcb Chapter 2 Review

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The dosage Form

Back 1

The form in which the drug is used, depends on the condition of the patient.

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Solid Dosage Forms

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Tablet

Lozenges

Capsule

Enteric Coated Tablet

Powders for inhalation

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The Tablet

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Made of pressed powder. How hard the powder is pressed determines how the tablet can be used, a sublingual tablet is made to dissolve quickly, under the tongue, and therefore cannot be pressed har into a dense tablet.

An example of a sublingual tablet would be a nitroglycerintablet, which is made to dissolve quickly so that the drug may be rapidly absorbed into the system.Most tablets are lightly coated with a protective coating ( a “film” coating) to protect the drug. Thisdoes not affect the absorption or dissolution of the medication. An enteric tablet is coated with a hardshell coating, designed to protect drug from acid in the stomach. The drugs contained in enteric tabletsare normally best absorbed in the basic pH of the duodenum. An exception is enteric coated aspirinwhich is coated so that it will not dissolve in the stomac and subject the stomach lining to its effects.Enteric coated tablet should not be split or crushed.

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The lozenge

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The lozenge: a hard tablet or molded shape containing drug in a sweetened, flavored base. THelozenge is designed to be held in the mouth while it slowly release drug for oral absorption. Thisdosage form is particularly useful for administration of pain medication for chronic pain and for therelief of nausea during cancer chemotherapeutic. Drugs available in lozenge form are listed above.

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Drugs Available in Lozenge Form

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morphine sulfate

Lorazepam

Haloperidol

Clotrimazole

Nystatin

Diphenhydramine

Metoclopramide

Dexamethasone

Benztropine mesylate

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The Capsule

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A capsule is a gelatin “container” filled with powdered drug, drug granules, a liquid drug formulation,or an oil. Example would be antibiotics capsules, liquid vitamins (eg. A,D, or E) and many over thecounter cold remedies.

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Powders for Inhalation

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In this dosage form, a very fine crystalline form of the drug (amicrocrystalline powder) is mixed with an inert guardian (e.g. lactose) and packaged into a single dose“blister”. The blister is then inserted into a special apparatus called a “disk halter” which pierces theblister, aerosolizes the drug, and allows the patient to inhale the medication.

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Liquid Dosage Forms

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Syrup

Elixir

Extract

Solution or Suspension

Tincture

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Syrup

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Is a sweetend liquid that contains drug, sugar, and flavoring.

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Elixir

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Similar to a syrup but contains a relatively high percentage of alcohol.

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Extract

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Is the oil or active portion of a plant or herb that is usually removed, or extracted with alcohol.

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Solutions and Suspensions

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If the drug dissolves completely into the liquid (eg. Syrup, elixir) it is called a solution. Another oraldosage form is th drug suspension which is composed of water and drug particles that do not dissolvebut remain suspended in the water. Suspensions need to be handled carefully, as the drug particles tendto sink to the bottom very quickly. Mixing and drawing the dose can be tricky the withdrawal of thedrug dose must be done immediately after mixing,before the drug particles have a change to settle. Ifthe suspension is not properly mixed or the does is not drawn immediately, the wrong dose of drug maybe dispensed. If the dose is taken from the top of the container, it may contain too much water and notenough drug. If it is taken from the bottom the Duran solution may be too concentrated because thedrug particles tend to sink. In addition to mixing the suspension thoroughly, how the sole is withdrawnmatters, as well The dose must be drawn up quickly, as the drug parts may settle while the dose is being drawn.

Drugs in suspension need to be handled carefully, as drug particles may settle to the bottom of theontianer while the dose is being withdrawn!

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Tinctures

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Tincture is another liquid dosage form. In modern time, its only used topically, The tincture is analcohol based drug form, such as tincture of mentholated, and is normally dispensed in a dropper bottle.These drugs are not to be taken internally

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Semisolid Dosage Forms

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Creams

Lotions

Ointments

Suppositories

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Creams and Lotions

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Creams and lotions are nothing more than emulsions ( oil droplets suspended in water), where the drug is usually dissolved in the oil. Creams are thicker, as they contain less water than lotions.

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Ointments

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Ointments may vary from a thick emulsion to a drug suspended in a waxy base, like petrolatum ( whichlike petroleum jelly, only stiffer and thicker). These preparations are usually used topically ( on the skinor mucous membrane, such as those in the mouth, inside the nose, or rectum) and are normallydispensed in a tube or jar.

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Suppositoreis

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Suppositories are made of wax and oils, and contain the drug that is meant to be released sowly, and ina particular place. They are normally inserted in to body cavities, such as the rectum or vagina, wherethey adhere to the cavity wall and release medication to the immediate area. Recital suppositories arealso used to medicate patients who cannot take medication orally (e.g. a vomiting patient), as themedication, if properly prepared, can be absorbed through the rectal wall into the bloodsream.Suppositories are normally large, and , being primarily made of soft wax, will melt at bodytemperature. They should be stored in a cool room or rgerated (depending on the drug), and handlingshould be kept to a minimum.

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Storing Emulsions

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Care must be taken when storing emulsions. Freezing the emulsion or exposing it to excessive heat(near a heat source, for example, or storage in a warm room for a long time) will cause the cream toseparate into oil and water. Emulsions should not be stored in the refrigerator and especially shouldnever be frozen, as the rapid change in temperature will cause the product to separate faster.

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Routes of Administration

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The route of administration denies how the drug gets into the body. Drugs to be administered bydifferent routes are prepared in different ways. The most common route of administration is by mouth(oral or PO). These drugs are given as a tablet or oral solution. Sublingual tablets (SL) are madedissolve under the tongue; the underside of the tongue and the floor of the mouth contain large amountsof blood vessels near the surface allows the drug to be absorbed into the system very quickly. Thesetablets are very soft and dissolve easily. Sublingual preparations are also marketed in a sprayformulation, which are sprayed under the tongue.

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Routes of Administration

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Intranasal

Transdermal

Inhalation

Administration through the body cavities

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Intranasal

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A drug in drop or spary form is propelled through the nasal cavity

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Transdermal

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A drug "patch" is used, which slowly releases drug into the skin, where it is picked up by surface blood vessels and absorbed into the body.

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Inhalants

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Drugs may be used in powder or liquid form, in combination iwht an inhalant apparatus, to be taken directly into the lungs

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Administration through the body cavities

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drugs may be used in cream or suppositoryform. They are inserted into body cavities, such as the vagina or rectum, and used forlocal administration (eg. for a yeast infection or a case of hemorrhoids, respectively).Rectal administration is also very useful for administration of drugs to a patient whocannot take medications orally, as the drug is absorbed through vessels in the rectal wall.

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Buccal Administration

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Drugs may also be administered through the lining of the cheek. This is termed buccal administration.The dosage form in a lozenge or buccal tablet, is inserted between the cheek and the gum.

Front 26

Medicating the Eye and Ear

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Drugs for the eye (ophthalmics) or ear (otics) are administered by drop (gtt). The dropper or droppercontainer is calibrated to give a drop of the particular size needed to give an accurate dose of drug.Ophthalmic ointments may also be used ( eg. antibiotic ointments) and are applied to the inside of theeyelid ( usually at the bottom of the eye). The top of the ointment tube should never touch the eye.

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Parenteral Drug Administration

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Any drug that is not given through the digestive system is given parenterally (para mean around andenteral refers to the digestive system). in normal medical terms, however, parenteral administrationrefers to drugs administered by injections. The three most common types of injections are theintravenous, intramuscular, and subcutaneous injections. Other types of injections include the intraarterial,intracardiac, intrathecal, and intradermal injections.

Intravenous

Intramuscular

Subcutaneous and Intradermal

Specialized Injections

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Intravenous injection preperations

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The Bolus

The IV Drip

The "Piggyback" IV

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The Bolus

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a one time single dose injection

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IV Drip

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A bag or bottle of liquid that allows drug to be infused over a long period of time

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The "Piggy Back" IV

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A solution contained in a smaller IV bag that is infused along with the primary intravenous drip, usually through the same tubing.

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Intramuscular Injections

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Intramuscular injections are placed into skeletal muscle. This allows the durg to enter the bloodstreammore slowly. This type of injections must first diffuse through muscle tissue before entering thebloodstream, so it requires a large bore needle in order to penetrate the muscle.The advantage to this type of injection is that the slow release of drug into the system minimizes shockto the system, allowing it to gradually acclimate to the effects of the drug.When preparing an intramuscular injections, a large-bore needle should be attached, as a small needlewill not easily penetrate muscle tissue.

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Subcutaneous and Intradermal Injections

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njections into or under the skin include subcutaneous and intradermal injections. Subcutaneousinjections are placed under the skin, which allows for a slow absorption of drug into the bloodstream.Intradermal (ID) injections, which are less common are placed within the skin layers. Both of thesetypes of injections must be dispensed with a very fine needle on the syringe.Intramuscular and subcutaneous injections provide for a slow rate of delivery of drug to the system

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Specialized Injections

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Intra-arterial Injections

Intrathecal

Intracardiac injections

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Intra-arterial Injections

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Occasionally drugs, need to be administered directly into an artery, in orderto have the best effect. These are called intra-arterial injections. Arteries are very muscular and theblood within them is under very high pressure, so these injections require a somewhat larger boreneedle.

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Intrathecal and Intracardiac Injections

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Intrathecal and Intracardiac injections are specializedinjections forms. Intrathecal injections are placed into the space between the spinal cord and spinalmeninges (eg. An epidural anesthetic during childbirth) and intracardiac injections are placed directly into the heart. These types of injections allow fact action of a drugn by placing the drug at the site ofthe organ itself

Front 37

Interpreting the Prescription Order

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Before filling the prescription order, you must first check the prescription form to make sure that the order isgenuine, legal, and complete. Certain information must be on the prescription form when it is received, and otherinformation may be filled in by the technician, unless the prescription is for a controlled substance. In this case,no information is to be added, deleted, or corrected on the prescription form.

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Required information to be on the prescription form

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The Drug Name

The Strength and Dosage form of the drug

The amount of drug prescribed

Instructions for the patient (SIG)

Signature of the Prescriber and Authorization to Substitute

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The Drug Name

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this can be generic ( the actual name of the drug) or a brand (proprietary)name. This prescription specifies the exact drug to select for dispensing. This prescription waswritten fro a brand name, Lasix, although the prescriber did sign on the “may substitute” line, sogeneric substitution is permissible.

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The Strength and Dosage Form of the drug

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Drugs come in different strengths and forms fordifferent needs. The strength and from must be specified, unless the drug comes in only oneform or strength. For example, some combination drugs such as trimethoprim withsulfamethoxazole combination or acetaminophen with codeine (Tylenol #3) are dispensed in aspecific dosage and proportion. Mannitol is dispensed only in a solution for injection. Theproportions and forms of these drugs do not need to be specified on the prescription form. Incontrast, Lasix tablet come in 20 mg, 40 mg, and 80 mg strengths, as well as in oral solution andsolution for injection. The dosage strength and form did need to be specified in the sampleprescription shown in Figure 2-5.

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The amount of drug Prescribed

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A prescription for tablet, such as that in Figure 2-1, mustspecify the number of tablets to be dispensed. For other dosage form, however, this may not bethe case. For example a prescription for a liquid dosage form may be specified in more than onway. Either the volume may be specified, or the drug dose may be specified in mg, g, and so on.A drug dose may be specified by volume or by equivalent weight of the drug.

Example: The prescription order is for 500 mL of 10% calcium gluconate solution. Since the volume was given,the specified amount of solution ( 500 mL) would be dispensed.

Example: The prescription order is for 200 mg of Minocin IV. Minocin comes in a sterile solution of 20 mg/ml. In this case, the volume of solution to be dispensed for a 200 mg dose would have to be calculated (eg. 200 mgdivided by 20 mg = 10 mL).

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Instuctions For the patient (SIG)

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This is where knowledge of the abbreviations inTable 2-1 comes in. Since the instructions must be written out for the patient, the technicianmust be able to accurately read the SIG. The prescription in Figure 2-5 states that one tablet(designated by a horizontal bar with one vertical bar and one dot) is to be taken twice a day (bid, or bis in deum) as needed (prn) for edema. The amount of medication to be taken, andlimitations on when or how often it is to be taken, must be included on the prescriptionform.

Front 43

The Half Life

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The spacing of the doses, or dosage interval, is extremely important, as the space between doses is based on thehalf life (T ½) of the drug. The T ½ is a measure of how rapidly a drug is cleared from the body, and gives anestimate of how quickly the effects of the drug will be terminated. (There are many ways in which the actions ofa drug may be terminated, but the half life is generally considered to be the main index of the length of a drugseffects).The half life can be used to predict the dosage interval for a drug. To keep the serum levels of a drug relativelyconstant, the drug should be replaced as it is cleared from the body. Thus, dosage intervals are very important,and the instructions for taking the drug must be communicated effectively to the patient. It is also important tocommunicate to the patient the proper use of the drug (eg. Proper insertion of a suppository, instillation of anopthalmic preparation etc.).The half-life of a drug is the amount of time taken for half of the serum concentration of drug to eliminated fromthe bod. It is used to establish accurate dosage intervals.

Example: The time it takes a drug to be eliminated from the body is around 5-7 half lifes. If a drug has a 6 hourhalf life then it would take 30-42 hours to be eliminated. (6hrs x 5 =30, 6hrs x 7 =42)

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Signature of the prescriber and authorization to substitute:

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The signature must behandwritten in Ink. The authorization to dispense a generic drug may be indicated in a boxon the prescription form, in which the letters DAW (dispense as written) are written( indicating that the exact proprietary label must be dispensed) or absent (indicating that asubstitution is permissible.) Depending on the state, the prescription form may contain thisbox or may have a duplicate of signature lines bearing a designation such as “ maysubstitute” or “ no substitution permissible”. If the prescriber designates “no substitutionpermissible” the drug must be dispensed exactly as written, in the correct form, strenght, andunder the specified proprietary label.

The “may substitute”option gives the pateint and pharmacy the option to choose a less expensive generic brandor another proprietary label, as long as the drug, strength, and form remain the same.

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Information to be filled on the prescription form by the technician

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The patients Address and Telephone number

The age or date of birth of the patient

Drug allergies

Concurrent medications

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The patients address and telephone number

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This information identifies the patient( there may be more than one patient with the same name). It also provides a means of contact with the patient, in case of a problem with a prescription or drug recall

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The age or date of birth of the patient

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This information is very important as it serves toidentify the patient ( eg. To distinguish between a father and son with the same name) andassures that the drug dosage prescribed is appropriate for the age o the patient ( drug dosagemay be reduced in a child or elderly person for example, as organ functions are lessefficient)

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Drug Allergies

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Many drugs are very similar in chemical structure and action. Thus, if apatient is allergic to one drug (eg. Penicillin), he or she may well be allergic to similar drugs,such as amoxicillin or even cephalexin. A history of drug allergies is critical to the care ofthe patient as it may help prevent an uncomfortable or even fatal allergic reaction.

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Concurrent Medications

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These are medications already being taken by the patient. Ahistory of concurrent medications should include not only other prescription medications butalso those purchased over the counter (eg. Cold remedies), and herbal remedies as well.( The first drugs were little more than pulverized plants, or plant extracts, after all. We havedone little more than refine them, in many cases.) Herbal preparations can have very potentdrug actions and interactions and must be recorded in the patient profile.

Many drugs interact with each other to produce adverse effects. A particular drug may also greatly increase thetherapeutic effects of another drug, which would require an adjustment to the patients dosage.

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Dispensing the Correct Medication

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Once the drug, dosage form, and strength have been established, the correct medication is selected. Thismedication should be exactly what appears on the prescription form.

Example: The drug order is for Compazine suppositories. You have Compazine solution for oral administrationin stock, but no suppositories. The order cannot be filled, as the dosage forms do not match (suppositories arenormally prescribed for patients who cannot take medications orally)

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Verifying The Medication Use of the Manufacturers Label

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Many drug names look alike and sound alike, so the manufacturer labels must be comparedcarefully to the prescription order.

Example: Extra letters may be present in the drug name on the label (eg., Adalat CC instead ofAdalat). This may mean the drug is a different formulation of the brand name drug ( in this casean extended release form) or may be a different drug altogether (eg. Quinine andquinidine).Some of those abbreviations can be found in Table 2-3. If the name of the drug doesnot match exactly, the drug shouldn't be dispensed.

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Verifying The Proper Dosage Strength

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The choice of dosage strength is less critical than other information. If the dosage strength does notmatch, it may be possible to convert dosages ( see chapter 4 and 14). If the dosage form is incorrect,however, the drug cannot be dispensed by the technician without consulting the pharmacist.

Example: The drug order is for 250 mg amoxicillin tablets. There are no tablets in stock, but the pharmacy doeshave amoxicillin suspension in stock for oral administration. Both dosage forms are for oral administration, sothe suspension could be substituted, with proper calculation and patient instruction ( this would require theapproval of the pharmacist).

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Extended Release Formulations

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LA: Long ActingSA: Sustained ActingSR: Sustained ReleaseTR: Timed ReleaseER: Extended Release

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Automated Unit Dose Delivery System

Back 54

There are several automated dispensing system presently marketed for in situational use. Once popularand innovative automated unit dose delivery system coming into widespread use in institutionpharmacy is the Pyxis Rx system. The Pyxis system is essentially a computerized cabinet that is locatedon a hospital floor (unit). The cabinet is stocked with drugs which are appropriate to the particularhospital unit where it is located. Like the med cart, drugs are filled in locked drawers withing thecabinet, and the units are maintained and stocked by pharmacy personnel. The computer within thePyxis unit is on a local are network, which interfaces with the main hospital computer. Thus, the unitactually charts patient medications as they are withdrawn form the cart by hospital personnel.

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Processing of Medication Orders Using thePyxis System

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The Pyxis system streamlines the dispensing of medication. Medication order are received as usualfrom physicians in the pharmacy. The pharmacy technician then enters the order into the main hospitalcomputer system. The orders are then checked by the pharmacist to ensure that the medications anddoses are appropriate for the age, weight, and diagnosis of the patient, and that therapeutic duplicationsand drug-drug interactions are not present. The order is then sent to the Pyxis system. Once the orderhas been verified and is present in the system, the floor nurse can enter appropriate information into thesystem when it is time for the patients medication. The system then allows the withdrawal of the properunit doses of medication for administration to the patient. Identification of the nurse, by thumb print orcode, must be received by the unit for the medication drawers to unlock and the medication to bewithdrawn.

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Advantages to the Use of Automated UnitDosing Systems

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The advantages to this system are many: Medication errors are reduced, as the medication is dispensedcomes directly from the original medication order ( ie. Not faxed, transcribed, or photocopied); drugdruginteractions are reduced; and patients receive their medication in a more timely manner allowingmore effective dosing. In addition, input from the pharmacist is almost instantaneous. Blood analysis ofdrug levels can also be included in the computerized information, allowing dosages to be adjustedalmost instantaneously. This provides better control over patient medication. Also as patients aretransferred from room to room and floor to floor, their information remains centralized with lesschange of record loss. Documentation of drug dispensing and administration is generated automaticallywith the system and can be printed out at any time, should a hard copy be needed.

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Comparison of Drug Dispensing in Retail and Institutional Settings

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Dispensing a prescription in an institutional setting is similar to the retail setting, with few execeptions.Several drugs are usually prescribed at once (see Chapter 1) using the hospital order; these doses maybe sent up to the patient individually ( eg. , a medication needed quickly, for an emergency [STAT], or amedication prescribed for pain, emesis, etc., which is not part of the usual routine of drugs), or placedinto a unit dose cart. Unit dose carts contain the daily medications of the patients on a particularhospital floor. They are prepared daily by technicians and then checked by pharmacists. Thesecomputerized carts contain the individual medications of patients on the floor, normally enough to last for one day. The carts are filled daily, from the physicians order for the various patients on the floor,making it easier for nurses to properly administer medications to patients. Narcotics prescribed “asneeded” may not be dispensed in a unit dose cart.