Date post: | 28-Dec-2015 |
Category: |
Documents |
Upload: | prudence-evans |
View: | 217 times |
Download: | 1 times |
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