Oral & Parenteral Dose - reference PDF

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Mathematics for Medication Administration

Calculation of Oral and Parenteral Doses

Calculation of Oral and Parenteral Doses Introduction In this module, you will learn the core nursing concept of dosage calculations. This skill will allow you to safely determine a dosage, based on a prescriber’s medication order. For instance, you will be able to calculate the volume of injectable medication required to satisfy a particular prescription. In addition, you will gain familiarity with various forms of oral and parenteral medications.

Overview x x x x

Forms of Oral Medication Routes of Parenteral Medication Delivery Calculation of Oral and Parenteral Dosages Validation of Dosage Calculations

Module Outcomes x x x x

Recognize various forms of oral and parenteral medications Interpret medication concentration as a ratio. Given a medication order and concentration, determine the number of tablets or volume of fluid required for a dosage. Mathematically validate a calculated dosage.

Forms of Oral Medication Oral medications are generally ingested by mouth. The medicinal ingredients are most often absorbed in the gastrointestinal (GI) tract. Tablets: x Scored Tablets x Sublingual Tablets x Time Release Tablets x Enteric-coated Tablets Capsules x Oral Capsules x Suppositories Oral Liquids x Oral Solutions x Oral Suspensions x Syrups

Mathematics for Medication Administration

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Calculation of Oral and Parenteral Doses

Elixirs

Administered by mouth using: x Tablet/capsule with water x Medicine cup x Oral syringe x Teaspoon/tablespoon

Tablets Tablets consist of powdered medication that has been pressed together with nonmedicinal binder ingredients. Binders help a tablet maintain its shape. Typically, a tablet contains enough medication for one standard dosage. Examples: x Tenormin (atenolol): a beta blocker used to reduce hypertension. x Aleve (naproxen): a non-steroidal anti-inflammatory drug (NSAID) used to treat fever, inflammation and pain. Scored Tablets Scored tablets have grooves indented into the surface of the tablet. This allows a nurse to cut these tablets in half using a specialized tool. For example, if a tablet contains 20 mg of medication, but a patient requires only 10 mg, then the tablet may be split in half. Generally, it is advisable to seek out a weaker strength, rather than cutting the pill. In this case, if 10 mg tablets are available, these would be more accurately measured than half of a 20 mg tablet. Note: Scored tablets can be cut in half using a pill cutter.

Examples: x Paxil (paroxetine): used to treat depression. x Imovane (zopiclone): used to treat insomnia. Sublingual Tablets

Mathematics for Medication Administration

Calculation of Oral and Parenteral Doses

Sublingual tablets are taken orally, but are not swallowed. These tablets are placed underneath the tongue, where they dissolve. The medication is quickly absorbed into the bloodstream through capillaries in the mouth. Examples: x Saphris (asenapine): an antipsychotic used to treat schizophrenia and bipolar affective disorder. x nitroglycerin: used to prevent or reduce the severity of angina. Time Release Tablets Time release tablets are designed to secrete small amounts of medication over a long period of time, when compared with traditional tablets. They may be designated as sustained release (SR), extended release (XR), or long acting (LA, XL). This time release feature is due to a specially-engineered coating. Accordingly, these tablets should not be split, chewed or crushed. Examples: x Wellbutrin SR (bupropion): used in the treatment of depression and for smoking cessation. x Xanax XR (alprazolam): used to treat symptoms associated with panic and anxiety disorder. Enteric-coated Tablets Enteric-coated tablets are designed to dissolve only upon reaching the small intestine. The coating of these tablets resists the harsh, acidic environment of the stomach and disintegrates only in the slightly alkaline intestinal fluid. Examples: x Dulcolax (bisacodyl): a laxative used to treat constipation. x Protonix (pantoprazole): a proton pump inhibitor used to treat ulcers in the duodenum (the upper small intestine).

Capsules Capsules consist of solid or liquid medication, contained in a rigid casing. They are administered whole and cannot be split, chewed or crushed. Capsules quickly dissolve in stomach acid, releasing a concentrated dose of medication; as such, they are used for quick delivery of oral medications. Time release technology is also integrated into some capsules. Examples: x Detrusitol (tolterodine): used to reduce urinary frequency in patients with overactive bladder syndrome. x Altace (ramipril): an ACE inhibitor used to treat hypertension and increase survival following a heart attack.

Mathematics for Medication Administration

Calculation of Oral and Parenteral Doses

Suppositories

Although suppositories are not taken by mouth, they are similar to other oral dosage forms. Suppositories are inserted into the rectum, vagina or urethra for targeted delivery of medication to specific tissues. Examples: x Glydolax (glycerol): used for the treatment of constipation. x Caverject (alprostadil): used for the treatment of erectile dysfunction (ED).

Oral Liquids Oral liquid medication is measured using medicine cups, teaspoons (5 mL) or tablespoons (15 mL). Medicine cups are available in standard volumes of 30 mL and 60 mL, with graduations typically measured at 5 mL intervals. For more precise measurements, and for paediatric applications, an oral syringe should be used. Liquid solutions consist of medication which is completely dissolved in water. This results in a liquid with fluid consistency. Examples: x Medrol (methylprednisolone): a glucocorticoid used as an anti-inflammatory drug. x Prozac (fluoxetine): a selective serotonin reuptake inhibitor (SSRI) used to treat depression. Oral Suspensions Oral suspensions contain medication that has not completely dissolved; rather, it exists as solid particles "suspended" in the fluid. Examples: x Amoxil (amoxicillin): a common antibiotic used to treat a range of bacterial infections. x Zovirax (acyclovir): an antiviral drug used to treat chickenpox and some herpes infections. Syrups Syrups contain medication in a viscous solution of sugar and water. In cough syrup, for example, this consistency helps situate the medication near the larynx for targeted delivery. Examples: x Prometh (promethazine): used in the treatment of allergic reactions and motion sickness. x dextromethorphan: an active ingredient in many cough suppressants. Elixirs

Mathematics for Medication Administration

Calculation of Oral and Parenteral Doses

Elixirs contain medication in a solution of alcohol and water. They are clear, aromatic and less viscous than syrups. Elixirs are used to mask the taste of the active ingredient, while increasing its solubility. Examples: x chlorphenamine: an antihistamine used to treat symptoms of a variety of allergic reactions. x Choledyl (oxtriphylline): a bronchodilator used to provide relief from breathing difficulties.

Routes of Parenteral Medication Delivery Parenteral medications are those which are delivered directly into body tissues by needle and syringe. These are referred to as hypodermic syringes to distinguish them from oral syringes.

Parenteral fluids take the form of medication solutions and suspensions. Due to their route of delivery, they bypass chemical processing by the GI tract and are quickly absorbed into tissues. Four common routes for delivery of parenteral medication: 1. Intramuscular (IM) Injections Intramuscular (IM) injections deliver fluid into large muscles. Common injection sites include muscles of the shoulder, thigh and buttocks. Typically, intramuscular injections do not exceed 3 mL in volume. Examples: 1. Valium (diazepam): a benzodiazepine used to treat muscle spasms, anxiety and seizures.

Mathematics for Medication Administration

Calculation of Oral and Parenteral Doses

2. Torecan (thiethylperazine): used to treat nausea and vomiting. 2. Intravenous (IV) Injections Intravenous (IV) fluids are delivered directly into a vein. As such, they rapidly spread throughout the body's organs and tissues. They can be quickly administered as an IV bolus injection over a number of minutes. IV bags, on the other hand, contain much larger volumes of fluid, which infuse into a patient's bloodstream over a number of hours. This therapy is referred to as IV infusion. Common IV injection sites include veins of the forearm, wrist and hand. Examples: 1. N/S (normal saline): a nearly isotonic (N/S has approximately the same concentration of sodium chloride (NaCl) as blood.) solution of salt in water used to treat dehydration, among several other uses. 2. morphine: acts directly on the central nervous system (CNS) to relieve severe pain. 3. Subcutaneous (subcut) Injections Subcutaneous (subcut) injections are administered into the subcutaneous layer of skin. This consists of fatty, adipose tissue, which is located beneath the dermis and epidermis, the top layers of skin. Common subcutaneous injection sites include skin of the lower abdomen, upper arm, thigh and upper back. Typically, subcut injections do not exceed 1 mL in volume. Examples: 1. insulin: administered as a supplement for type I diabetics to lower bloodglucose concentration, preventing hyperglycaemia. 2. heparin: an anticoagulant used to prevent the growth and formation of blood clots, which may lead to heart attack, embolism or stroke. 4. Intradermal (ID) Injections Intradermal (ID) injections deliver medication within the dermis layer of the skin. Common sites of administration include the forearm, upper arm, chest and upper back. They are often used in diagnostic tests for allergic reaction. Typically, intradermal injections do not exceed 0.1 mL in volume. Examples:

Mathematics for Medication Administration

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Calculation of Oral and Parenteral Doses

tuberculin: used in the PPD (the purified protein derivative test, also known as the tuberculosis skin test) skin test to determine previous exposure to tuberculosis-causing bacteria. lidocaine: used as a local anaesthetic in preparation for surgery.

Parenteral fluids are most commonly available in vials. These containers may hold enough medication for several doses. Vials are often sealed with stoppers that are designed to be needle-punctured. This allows one to draw up a dosage with a syringe without opening the vial and risking contamination of its contents. These vials are often vacuum-packed to prevent degradation of the medication. In this case, air must first be injected into the syringe before drawing up a dose.

Parenteral fluids can also be packaged in ampules (abbreviated amp). Ampules contain one standard dose of medication. The glass is scored at the neck and can easily be broken to access the fluid. Ampules are packaged in boxes, which are labelled with information regarding concentration, volume, storage details, etc. Each box holds several ampules.

Mathematics for Medication Administration

Calculation of Oral and Parenteral Doses

Types of Syringes There are several types of hypodermic syringes, which are distinguished only by their capacity and markings.

The tuberculin skin test (PPD) typically requires a very small and precisely measured dosage of tuberculin. Thus, tuberculin syringes have many fine graduations and are accurate to within 0.01 mL. These syringes can also be used for other medications that require precise measurements, such as heparin and paediatric medication.

Insulin syringes have volume graduations that are measured in "units". These units are specific to a particular concentration of insulin, and are unrelated to other medications that are also measured in units. In order to avoid overdosing of this very common and potentially lethal medication, insulin is typically ordered, measured and administered solely in terms of units. This eliminates the need for dosage calculations for nurses and self-medicating patients, alike.

Mathematics for Medication Administration

Calculation of Oral and Parenteral Doses

Calculation of Oral and Parenteral Dosages Dosage Calculations A medication order will require a certain amount of medication per dose, usually measured in g, mg, or mcg. On hand, you will have tablets, capsules or liquid medication, labelled with a concentration (for example: g/tab, mg/cap, or mcg/mL). Your job is to figure out how many tab, cap or mL are required to satisfy the medication order. Dosage Calculation Example: Order: 300 mcg of Cytotec, orally. Supply: bottle of Cytotec labelled 100 mcg per tablet. How many tablets will you administer to the patient? In this example, you need to give the patient 300 mcg of Cytotec. Each tablet contains 100 mcg of Cytotec. So, if you administer 3 of these tablets, the patient will receive 300 mcg of Cytotec altogether. Notice here that the phrase "100 mcg per tablet" is quantitative information that can be translated into a ratio. 100 mcg per tablet means 100 mcg : 1 tab. Quite often, medications are available in multiple different strengths. Suppose you find a bottle that is labelled '150 mcg per tablet'. Here, the patient would require only two tablets to satisfy the order of 300 mcg. Note: This concentration does not mean that the tablet itself weighs 150 mcg; rather, there are 150 mcg of medicinal ingredients contained within each tablet. The remaining mass consists of excipients (non-medicinal ingredients) which act as binders, for example. There is a more mathematically rigorous method to calculate dosages. This will be required as problems become more complex! For any given dosage calculation, there will be: a) a medication order, b) a goal unit, and c) a concentration, which is a ratio relating the medication order to the goal unit.

Recall the example: Order: 300 mcg of Cytotec, orally.

Mathematics for Medication Administration

Calculation of Oral and Parenteral Doses

Supply: bottle of Cytotec labelled 100 mcg per tablet. How many tablets will you administer to the patient? a) a medication order: 300 mcg, b) a goal unit: tab, and c) a concentration: 100 mcg per tablet....