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

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

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

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

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 Sunscreen o Antibiotic ointments o 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