Clinical Calculation 5 th Edition Chapter 6 Calculation of Oral Medications Pages 40 - 54

Clinical Calculation5th Edition

Chapter 6

Calculation of Oral Medications

Pages 40 - 54

Oral Medications

Medications that are administered by mouth and absorbed via the gastrointestinal tract are known as PO (by mouth or orally) drugs.

Variation of the oral route is called sublingual (sL) route, whereby medication is placed under the tongue for absorption via the mucous membrane.

Buccal route, medication is placed between cheek and gum for similar absorption.

Neither sublingual nor buccal medications should be chewed or swallowed whole, as a rule they are not followed by water.

Finally it is important to know different forms of oral medication and symbol used and understand how to read labels of medication containers, and calibrating on equipment used to dispense liquid medications.

Oral medication forms

Tablets Contain a powered drug compressed into a tablet

Coated tablets Covered with flavored coating to help swallowing and taste

Enteric coated Delay dissolution till it reaches intestine, no dividing or crushed

Capsules Gelatin container to conceal taste, ok to open and placed in the food

Caplets Looks like capsules it may be coated, but it should not be broken

Sustained-release capsules or tablets (time release) Coated to dissolve at different time, should not be broken.

Liquids Dispensed as elixirs, syrups, suspensions or solutions

Pictures

The medicine cup

Basically there are 3 different type of measuring cups that we deal with here, and they are collaborated in one or more of the 3 measuring systems Metric system Apothecaries system Household system

When solution is poured into a cup – page 42

Concave surface is called meniscus and reading should be done at its lowest point.

Read the amount in a cup at the eye level and on the flat surface setting.

Look and note the smallest collaboration amount in each cup. When measuring smaller amount use syringe for accuracy if not pre-measured. You may use syringe and/or administer with spoon.

check and double check before administrating to make sure it is done correctly, it may require to be opened at the bedside for one more opportunity for correct dosage.

If between factors use syringe to collaborate the correct amount.

It measuring in teaspoon or tablespoon, round to nearest tenth

When administrating tablets

Tablet is scored in half or quarter Use pill splitter to score un-scored pills If oral medications that are not to be broken/ and it

require ½ quantity, consult the pharmacist or the physician in regard to rounding

Can be broken Tablets

Contain a powered drug compressed into a tablet

Capsules Gelatin container to conceal

taste, ok to open and placed in the food

Can not be broken Enteric coated

Delay dissolution till it reaches intestine, no dividing or crushed

Caplets Looks like capsules it may be

coated, but it should not be broken

Sustained-release capsules or tablets (time release)

Coated to dissolve at different time, should not be broken.

Reading labels and calculating dosage

Name of the drug and its generic name Dosage strength: amount or concentration of the drug, per mL,… Name of manufacturer Form: liquid-mL, tablet,… Expiration date Lot number- manufacturer's code in order to be able to track and

trace incase of recall. Total amount per container. Direction for administration (or scoring), mixing, shaking Bar code

Recommendation for storage (not on the list) Web site:

http://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm?fuseaction=Reports.ReportsMenu

The label for a bottle of medication is shown.

1. Identify the manufacturer's name. 2. Identify the dosage strength of the medication3. Identify the generic name of the medication.4. Identify the form of the medication.5. Identify the trade name of the medication.

1. Pfizer

2. 20 mg

3. piroxicam

4. Capsules

5. Feldene

Order: Lasix 20 mg PO

How many tablets should be administered?

1. Starting factor = ORDER2. Answer unit3. Equivalents equation4. Conversion equation

Order: Aldactone 50 mg PO


1. Identify the manufacturer's name.

2. Identify the dosage strength of the medication

3. Identify the generic name of the medication.

4. Identify the form of the medication.

5. Identify the trade name of the medication.

6. Total amount in the container


Order: Augmentin 500 mg PO

How many mL should be administered?


Order: Calan SR 240 mg PO

How many caplets should be administered?

1. Identify the manufacturer's name. 2. Identify the dosage strength of the

medication3. Identify the generic name of the

medication.4. Identify the form of the medication.5. Identify the trade name of the

medication.6. Total amount in the container


Order: Brethine 5 mg PO






Calculation based on body weight

Prescription may prescribed according to a designated amount of drug per kilogram or pound.

Because the amount of medication to be given is determined by the weight of the person, the weight and calculated dosage considered an equivalent relationship.

Starting factor for this type of the problem is in pound or kilogram.

Answer label is in whatever units the medication is dispensed (e.g., mL, mg, tab, etc.).

Use dimensional analysis to calculate the correct amount to be administered per dose.

Order: Mintezol Suspension 25 mg per kg per dose PO for an adult weighing 60 kg

Available Supply: Mintezol Suspension (thiabendazole) 500 mg per 5 mL How many mL should be administered per dose?

1. Starting factor = weight2. Answer unit3. Equivalents equation4. Conversion equation


Order: Myambutol 15 mg per kg per dose orally for an adult weighing 118 lb

Available Supply: Myambutol (ethambutol) 400 mg per tab How many tablets should be administered per dose?


A client who weighs 62 kg is to receive Nydrazid 5 mg per kg per day PO. The drug label states: Nydrazid (isoniazid) 300 mg per tab. Use dimensional analysis to calculate the correct number of tablets to be administered per dose.


Use dimensional analysis to calculate the correct amount to be administered per dose. Order: Augmentin 20 mg per

kg per day in divided doses PO every 8 hours for a client who weighs 38 kg.

Remember to divide by the number of does per day.


Order: Ancobon 50 mg per kg per day PO in divided doses every 6 hours for a client who weighs 176 lb

Available Supply: Ancobon (flucytosine) 500 mg per capsule

gn

Remember to divide by the number of does per day.


Chapter 8

Calculation of Parenteral Medications

Pages 83 - 127

Parenteral Medication

Medications that are administered via injection into dermal or intramuscular tissues or directly into vein are called parenteral medications.

Administered by route outside the gastrointestinal tract. Parenteral route

1. Intradermal (ID) -Chap 8

2. Subcutaneous (subcut) -Chap 8

3. Intramuscular (IM) -Chap 8

4. Intravenous (IV) -Chap 10 and 11

5. Intrathecal -not covered

6. Intracardial -not covered

7. Intra-articular -not covered

The Syringe and Needle

Syringe Needle –for penetration of the medication and the choice of needle

depends on the route and site of administration, the size and obesity of the client, and viscosity of the medication.

Hub – lower end of the syringe and holds the needle. Barrel –holds the medication Plunger –made of clouded, color glass or plastic and it is operated to fill

or empty the barrel Safety shield to protect its sterility for transport for injection and be

locked into place to provide a permanent shield for disposal following injection, some syringes comes with retractable technologies which automatically retracts into the syringe barrel after injection.

PlungerBarrelHubNeedle

The type of syringes

The tuberculin syringes Measures a total of 1 mL, and it is

calibrated in hundredths (0.01 mL) and also in minims (16 minims per mL)

Used for small quantities of medication and usually used with a 5/8” long needle

The insulin Syringes Collaborated in Units and should be

used only for administration of insulin. If very small quantity of medication ordered, it is also possible to use Tuberculin syringe, it requires conversion to mL or minims.

It is available in 0.3 mL, 0.5 mL and 1 mL.

The 0.5, 3, 6, 10, 12, and 35 mL Syringes Smaller ones are calibrated in 0.1 mL

and larger ones 10, 12 are calibrated in 0.2 mL

The type of Needles

The choice of needle depends on the route and site of administration, the size and obesity of the client, and viscosity of the medication. Varies in length from ¼” to 3”.

Shorter needles (1/4” – 1”) are used for intradermal or subcutaneous injections

Longer needles (1”- 2”) are used for intramuscular injections, irritating medications, and larger or obese clients.

Diameter of the needle is indicated by a gauge number. Runs from 14 to 27, the larger the number , the smaller the

diameter of the needle Fine needles are used for aqueous solutions and heavier

needles for suspensions and oils.

Bevel – the angle point of the needle increases the sharpness of the needle

See page 87 for pictures

Reading the Syringe

On most single use syringes the plunger has a rubber tip that has 2 rings in contact with the barrel. Measurement must be made at the top ring, the one closer to the tip in order to read the accurate dose.

Read at this point and Not here

Read the following syringes

1.2 mL

6.4 mL

.38 mL

Rounding OFF

Because clinical calculation does not round to nearest collaborate syringe size, it is necessary to round off these values. When calculating dose obtained does not results in

tenths of milliliter, the carry your decimal to hundredths and then

For 5 or more round upFor less than 5 (4 or less) round down

If using tuberculin syringe, it is possible to measure hundredths of mL. Therefore, the computation should be carried to thousandths and then round off to hundredths.

2.36 = 2.4

2.34 = 2.3

Parenteral Medication Forms

Drugs for parenteral medication are available in a variety of forms. Some are powder or frozen form and it must be reconstituted to a liquid, where as others are in solution and are dispensed in Single Dose ampoules – constricted stem that

facilitates snapping them open Single- and Multiple-dose Vials – the vial is entered

through the rubber diaphragm Pre-filed Cartridges – single-dose disposable

cartridges, may or may not be a needle attached to the cartridge.

Reading Labels

Manufacturer’s product insert describes, in detail, the composition of the drug, its action, indications and contraindications for use, precautions and adverse reactions, dosage, direction for dilution or reconstitution, and if necessary direction for administration.

See sample on pages 93-94

Calculating dosages obtained from Premixed Solutions

Many parenteral drugs are dispensed in vials or ampoules that contain single or multiple doses.

Label or printing on each container indicates the amount and the solution strength of the contents.

Use this values as equivalent when calculating quality of solution is needed for the required dosage.

Read label

1. Identify the manufacturer's name. 2. Identify the dosage strength of the medication3. Identify the generic name of the medication.4. Identify the form of the medication.5. Identify the trade name of the medication.6. Total amount in the container

Read Label





Calculate the correct amount to be administered per dose. Order: diazepam 2.5 mg IM

1. Starting factor = order2. Answer unit3. Equivalents equation4. Conversion equation

1. Identify the manufacturer's name. 2. Identify the dosage strength of the medication3. Identify the generic name of the medication.4. Identify the form of the medication.5. Identify the trade name of the medication.6. Total amount in the container 7. The medication should be stored below what temperature?

Calculate the correct amount to be administered per dose.

Order: Robinul 0.2 mg IM


A client is to receive chlorpromazine HCl 20 mg IM. The available supply is labeled Thorazine (chlorpromazine HCl) 25 mg per mL. How many milliliters should the nurse withdraw for the IM injection?


Prescription order states: trimethobenzamide 0.2 g IM. The vial of medication is labeled trimethobenzamide 100 mg per mL. How many milliliters should the nurse withdraw for the IM injection?

Calculations based on Body Weight

Method of calculating based on the body weight is similar to the method used in Parenteral dosages.

You have to start from client’s body weight.

Use dimensional analysis to calculate the correct amount to be administered per dose. Carry the answer to the hundredths place and round to the nearest tenth.

Order: isoniazid 5 mg per kg per day IM for an adult weighing 45 kg (maximum 300 mg per day)

Available Supply: isoniazid 100 mg per mL

Use dimensional analysis to calculate the correct amount to be administered per dose. Carry the answer to the hundredths place and round to the nearest tenth.

Order: Amikin 10 mg per kg as a loading dose for an adult weighing 125 lb

Available Supply: Amikin (amikacin) 250 mg per mL

Reconstitution of Drug in Powder Form

Some drugs lose their potency a short time after being placed in solution, so they are not reconstituted until they are ready to be used.

A sterile diluents, usually water or 0.9% sodium chloride (normal saltine) must be added according to directions on the label or manufacturer’s inserts.

Label must indicate for “injection” or “for injection”. It is important that only diluents designed in the directions be used for reconstitution, because they have been determined to be compatible with the drug or the IV solutions to which the drug will be added.

If asked for water do not added 0.9% sodium chloride.

Powder Form

After the diluents is added, the vial must be shaken to dissolve the powder, then it may be drawn up into syringe for administration.

Diluents volume May expand the volume of the solution. May not expand the volume of the solution. Read the drug label closely to make sure correct

strength or concentration of the reconstituted solution to use for correct volume in your calculation.

Read label


Refer to the information on the medication package provided. In addition to the IM administration route, by which other route can the medication shown be administered?

Intravenous

Units of Medication Some drugs are measured in quantities called units. It is frequently is used for hormones, vitamins,

antibiotics,… Because the type of effect varies for each drugs, there is

no common definition for a units.

Read Label


Use dimensional analysis to calculate the correct amount to be administered per dose. Round to the nearest tenth. Calculate the number of mL to be administered for the loading dose. Indicate this amount on the syringe.

Order: heparin sodium 3500 units subcut

Read label


Use dimensional analysis to calculate the correct amount to be administered per dose. Carry the answer to the hundredths place and round to the nearest tenth. Calculate the number of mL to be administered for the loading dose

Order: Pfizerpen 3.2 million units in 4 divided doses per day

Use dimensional analysis to calculate the correct amount to be administered per dose. Round to the nearest tenth. Calculate the number of mL to be administered for the loading dose.

Order: Pfizerpen 400,000 units IM

Available Supply: reconstituted supply of Pfizerpen (penicillin G potassium) 500,000 units per mL


Chapter 9

Administration of Parenteral Medications

Pages 138 - 142

Insulin Preparations Person with diabetes caused by insulin-secretion

deficiency may be treated by one or more injection daily of manufactured insulin.

Regular insulin is clear solution designated by letter R on the bottle. It is the only type of insulin that can be administered intravenously.

Modified insulin designated by L (Lente Insulin), N (NPH insulin) and U (Ultralente insulin). They can only be administered subcutaneously.

Lantus is a long acting synthetic human insulin administered subcutaneously.

Combination of regular and modified insulin may have been ordered. Such combination may be reported as proportions of regular and modified.

Read Label

State the dosage strength of the insulin.

100 units per mL

Which of the following syringes should be used to administer the order? Answer using the name of the correct syringe.

Order: Humulin 50/50 insulin 18 units subcutaneously

Unit-100

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Clinical Calculation 5 th Edition Chapter 6 Calculation of Oral Medications Pages 40 - 54