Basic Pharmacology Chapter 6 Pharmacology Study of drugs

Basic Pharmacology Chapter 6

Pharmacology • Study of drugs and their actions on living organisms • Drug Names: – Drugs have different names, many have similar spelling. • Exact names and spelling are imperative

Drug Names • Chemical Name: – Exact chemical structure of a drug • Ex. 4 -Thia-1 -azabicyclo[3. 2. 0]heptane 2 -carboxylic acid, 6[(aminophenylacetyl)amino]-3, 3 -dimethyl-7 -oxo-, [2 S-[2α, -5 α, 6β(S*)]]- • Generic Name: – Drugs common name • Ex. Ampicillin • Official Name: – Name under which the drug is listed by the FDA • Ex. Ampicillin, USP • Trademark: – Brand or Trade name – Only the manufacture who owns the drug can use the brand/trade name • Ex. Principen, Polycillin

Drug Classifications • Drugs are classified by: – Body System • Which body system the affect? – Therapeutic use or clinical indications • What disease or illness is being treated? – Physiological or chemical action • What does the drug do in the body? – Prescription or non-prescription • Does the medication require a prescription or can it be purchased OTC? – Illegal Drugs • Is the drug used for non-therapeutic reasons?

Basic Principles • Drugs act in the human body in the following ways: – Drugs change a physiological activity within the body • They do no create new responses – Ex. Blood Pressure Medication – Drug forms a chemical bond within specific sites (receptors) within the body • Relationship between drug and receptor is like a key

Basic Principles (continued) • Agonist: – Drugs that interact with a receptor to cause a response • Antagonist: – Drugs that attach to a receptor but do not cause a response • Partial Agonist: – Drugs that interact with a receptor to cause a response but prevent other responses

4 Stages • All drugs go through 4 Stages: 1. 2. 3. 4. Absorption Distribution Metabolism Excretion

Absorption • Process by which a drug is transferred from its site of the body entry to circulating body fluids (blood, lymph) for distribution – Rate of absorption depends upon: • • • Route of administration Blood flow through the tissue where drug administered How well the drug can dissolve (solubility) Proper reconstitution and dilution of drugs Administration into the correct tissue

Absorption (continued) • Routes of Administration: – Enteral: • Drugs administered directly into the GI tract – Ex. Orally – Parenteral: • Drugs administered that bypass the GI tract – Ex. Injections » Subcutaneous • Beneath the skin » Intramuscular: • Within a muscle » Intravenous: • Within a vein – Percutaneous: • Drugs administered through the skin or a mucous membrane – Ex. Inhalation, sublingual and topical

Absorption (continued) • Absorption of drugs applied to the skin (topical) in influence by: – Amount and strength of drug – Length of contact time – Size of the affected area – Thickness of the skin surface – Tissue hydration – Skin condition—intact or non-intact

Distribution • The ways drugs are transported by circulating body fluids to the sites of action (receptors) and to the site of metabolism & excretion – Organs with the greatest blood supply (heart, liver, kidneys & brain) receive the drug most rapidly – Tissues with lesser blood supply (muscle, skin, fat) receive the drug move slowly • Once absorbed, a drugs distribution rate is determined by: – Chemical properties – How the drug is affected by the blood and tissues it contacts

Metabolism • Process by which the body in-activates drugs – Liver is the primary site for drug metabolism • Other tissues & organs that metabolize drugs: – White Blood Cells – GI Tract – Lungs – Other factors that help to regulate drug metabolism • • • Genetics Environment Physiology Other drugs Illnesses Age

Excretion • Elimination of a drug from the body – Urine and feces are the primary routes – Other routes of elimination include: • Evaporation from skin • Exhalation from lungs • Secretion into saliva & breast milk

Drug Action • No drug has a single action – When a drug is absorbed & distributed, the desired action (expected response) usually occurs • All drugs can affect more than one body system, therefore potentially causing side effects and adverse drug reactions – Side Effects: » Unintended reactions to a drug given in a normal dose – Drug Reaction: » Unintended effect on the body from using a legal drug, illegal drug or 2 or more drugs • Each drug has parameters—therapeutic actions to expect, side effects to expect, adverse drug reactions to report and probable drug interactions. – Dosages are adjusted and monitored for the nest therapeutic effect

Allergic Reactions • Unfavorable response to a substance that causes a hyper-sensitivity reaction. – Occur in persons previously exposed to a drug • Person develops antibodies to the drug, on re-exposure the antibodies cause a reaction – Most common reaction: » Urticaria (Hives) – Anaphylaxis » Severe, life threatening sensitivity to an antigen • Sweating, shortness of breath, low blood pressure, irregular pulse, respiratory congestion, swelling of the larynx, hoarseness, dyspnea

Reactions • Mild Reactions – Warning to not take medication again • Anaphylaxic Reaction: – Never use the drug again – Receive information about the drug – Tell health professional about the reaction – Wear a medical alert bracelet

Factors Influencing Drug Action • Some people react differently to same drug at the same dosages – Factors that affect a person’s response to a drug: • • • Age Body Weight Metabolic Rate Illness Willingness to take drugs Placebo effect Tolerance Dependence Cumulative Effect

Drug Interactions • Drug interaction occurs when the action of one drug is altered by the action of another drug – Occurs in 2 ways: • Drugs, when combined, INCREASE the actions of one or both drugs • Drugs, when combined, DECREASE the effectiveness of on or both drugs

Drug Information • With thousands of drugs it is impossible to memorize information about all of them – Be familiar with resources: • • American Hospital Formulary Service Drug Information Drug Interaction Facts Drug Facts and Comparison Handbook of Nonprescription Drugs Natural Medications Comprehensive Database Physicians Desk Reference (PDR) Package Inserts