Pharmacologic Principles

Jan Bazner-Chandler RN, MSN, CNS, CPNP

Chapter 2

Pharmacology

The study or science of drugs Knowledge of pharmacology allows nurse to

understand how drugs affects humans.

Naming the drugs

Chemical name Generic name Trade name

Chemical name

Chemical composition and molecular structure

Generic Name

Shorter and simpler than the chemical name

Trade Name

Drugs registered trade mark

Generic and Trade Name

Generic name: acetaminophen Less expensive – chemically similar to trade

name drugs Trade name: Tylenol, Tempra, Datril

More expensive

Pharmaceutics

How dosage forms influence the way in which the body metabolizes a drug and the way the drug affects the body.

Dosage Forms

A variety of dosage forms exist to provide both accurate and convenient drug delivery systems.

These delivery systems are designed to achieve a desired therapeutic response with minimal adverse effects.

Dosage Forms

Enteral: taken by mouth or PO Parenteral: intramuscular or intravenous Topical: applied to the skin, a patch,

suppositories (rectal or vaginal)

Dosage Form

Parenteral Injections Solutions Suspensions Emulsions Powders for reconstruction Sublingual or buccal

Chewable Tablets

Chewable Tablets

Can be chewed Used for children Used in the client that has a hard time

swallowing pills Break down of the drug starts in the mouth

Tablet

Tablets

Are made to be swallowed whole Are often scored so a half-dose can be give

Capsules

Capsules

To be swallowed whole Often are sustained release – 12 or 24

dosing

Enteric Coated Tablets

Enteric coated

Tablets are coated so that they do not break down in the stomach

Absorption of the drug takes place in the small intestine.

Cannot be divided into smaller doses

Sublingual

Sublingual

The tablet is put under the tongue Medication is absorbed through the buccal

mucosa. Used in drug like nitroglycerine used to

reduce chest pain.

IM and SC

Intramuscular or subcutaneous

IM or the “shot” – injected into the deep muscle of buttocks, thigh or upper arm Antibiotics Pain medications

Subcutaneous – injected into the fat layer just below the skin Insulin Anticoagulation meds: Heparin of Lovenox

Intravenous or IV

Intravenous or IV

Medication is administered right into the vein. Medications is readily absorbed right into the

circulation. Antibiotics Regular insulin only Pain medications Anti-nausea or anti-emetics Chemotherapy

Local Administration

Adhesive patches pain control nitroglycerine patches Hormones birth control patches nicotine patches

Topical Applications

o Sunscreeno Antibiotic ointmentso Cortisone

Eye, Ear and Nose Drops

Drops written as gtts

Eye Drops or Eye Ointment

Ear Drops

Vaginal or Rectal (PR)

Rectal Suppositories

Excellent route of administration of medications for the client that is: Vomiting / nausea Refuses to take medication PO Difficulty swallowing a medication Infants – fever or pain medications

acetaminophen (Tylenol) Suppository

Pharmacodynamics

The mechanism by which specific drugs produce biochemical and physiologic changes in the body.

Pharmacokinetics

Movement of drugs across body membranes to reach the target organ.

4 ways drugs move throughout the body: Absorption Distribution Metabolism Excretion

Absorption

Process that occurs from the time the drug enters the body to the time it enters the bloodstream to be circulated.

Onset of drug action is largely determined by the rate of absorption.

Absorption

Think of how the drug gets into the circulatory system and the dosage needed to bring the blood levels up to therapeutic levels. Dosage Interval of administration Route of administration

Oral Drugs or PO Drugs

Dosage is determined by how much of the drug is required to be taken by mouth to given the desired affect.

Bioavailability – portion of the drug that reaches the systemic circulation.

First-pass

If a drug is metabolized by the liver before it reaches the systemic circulation, some of the active drug will be inactivated or diverted before it can reach the general circulation.

Most drugs administered by mouth have less than 100% bioavailability.

Drugs administered by the intravenous route have 100% bioavailability.

Critical thinking question

What are the effects on bioavailability in: The infant that has an immature liver. The geriatric patient with a poor functioning liver The client with liver disease.

Where does absorption happen? Very few drugs actually absorbed in the

stomach (alcohol) Small intestine

large surface area for absorption of nutrients and minerals

most drugs absorbed in small intestine

Degree and Rate of Absorption Depends on

Route Age and physical condition of client Lipid or water solubility of drug Potential drug interactions with other drugs

What else might influence oral drug absorption? Food in stomach Certain juices – grapefruit juice Milk – binds with molecules of some drugs so

that the drug is never absorbed Orange juice – enhances absorption of iron

taken orally The coating on the tablet: chewable, enteric

coated, slow release capsules

Distribution

Transportation of drug molecules within the body after the drug is absorbed into the blood stream.

Distribution

Drug needs to be carried to the site of the action. Carried by the blood and tissue fluids to the sites

of pharmacological action. Distribution depends on adequacy of blood

circulation.

Key Concepts of Distribution

Protein binding – drug molecules need to get from the blood plasma into the cell.

Protein binding allows part of the drug to be stored and released as needed.

Some of the drug is stored in muscle, fat and other body tissues and is gradually released into the plasma.

Just how does the drug get into the cell? Drug must pass though the capillary wall Blood brain barrier – very effective in keeping

drugs from getting into the central nervous system or CNS – limits movement of drug molecules into brain tissue

Metabolism

Method by which the drugs are inactivated or biotransformed by the body.

Most drugs metabolized in the liver by cytochrome P450 (CYP) enzyme.

Hepatic drug metabolism or is major mechanism for terminating drug action and eliminating drugs from the body.

What can stop this process?

Enzyme inhibition Other drugs Combination drugs Liver disease Impaired blood circulation in person with heart

disease Infant with immature livers Malnourished people or those on low-protein diets

An important concept!

First-pass effect – some drugs are extensively metabolized or broken down in the liver and only a part of the drug is released into the systemic circulation

This is why dosage is important – how much drug needs to be taken in to give the desired effect and how often does it need to be taken

Excretion

Refers to the elimination of the drug from the body.

Requires adequate functioning of the circulatory system and organs of excretion. Kidneys via urine – most drugs excreted in the

urine Liver via bile and into the feces Lungs via exhaled air Saliva, tears and sweat or skin

Important concepts

Absorption – small intestine, skin, rectal or vaginal tissue

Metabolism – liver Distribution – circulation (blood or plasm) Excretion – urine, stool, skin

Dosing Schedules

Determined by drug’s pharmacokinetic properties Route of administration Onset of action Peak concentration level Duration of action Half-life

Onset, Peak, Elimination

Onset of action The time when the drug’s effects first become

noticeable.

Peak Concentration

Maximum blood concentration level achieved through absorption; at this level most of the drug reaches the site of action and provides therapeutic response.

Duration

Duration of action: the length of time a drug acts on the body.

Half-life

The time required for a drug’s plasma concentration to decrease to 50%.

Pharmacodynamics

Study of what the drug does to the body.

Pharmacotherapeutics

Therapeutic effect: the clinical indication for administering the drug. Prevent disease Treat disease

Preventive

Immunizations

Treat Disease

Acute therapy Maintenance therapy Supplemental therapy Palliative therapy Supportive therapy Prophylactic therapy

Acute Therapy

Intensive drug therapy implemented in acutely ill clients

Often used to sustain life or treat disease ICU Emergency Treatment Cardiac Resuscitation Septic shock – IV antibiotics

Maintenance Therapy

Prevent progression of the disease Insulin for diabetes Anti-hypertensive drugs to control hypertension or

high blood pressure Control chronic illness Cholesterol control

Palliative Therapy

Make client as comfortable as possible Pain control in cancer clients Oxygen for client with pulmonary disease

Supportive Therapy

Maintains integrity of body functions while client is recovering from illness or trauma Intravenous fluids to prevent dehydration Blood for anemia or blood loss

Prophylactic Therapy

Given to prevent illness or infection Antibiotics prior to dental surgery Antibiotics prior to orthopedic procedure

Most important job of the nurse! Monitoring the patient for effectiveness of

therapy. Response to medication needs to be

evaluated. Did the medication work! Monitor for adverse effects

Adverse Drug Reaction

Adverse drug reaction ADR: refers to unwanted or potential harmful effects of a drug; all drugs have one or more adverse reactions in addition to having the desired effect.

Classification of Adverse Reactions• Drug related reactions• Sensitivity-related reactions

• Hypersensitivity• Anaphylaxis

• Toxicity • Unexpected or peculiar response to a drug

Interactions

Drugs can interact with other drugs or food. Drugs can interact with other drugs In the drug history always ask about OTC

and herbal therapy that may interact with prescribed medications.

Nursing Responsabilities

Always check to seen when medication should be taken With food On an empty stomach Before meals After meals Specific foods that may need to be avoided