Introduction to Pharmacology

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Introduction to Pharmacology
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What is Pharmacology?

• The science of pharmacology involves the action
  of drugs on humans and animals.
• The aim of drug therapy is to diagnose, treat,
  cure, or lessen the symptoms of disease.
• The study of pharmacology applies properties and
  knowledge of drugs, mechanism of drug action,
  anatomy and physiology, and pathology,

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Drug Nomenclature

• All drugs are identified by a generic name, a
  chemical name, and a proprietary (brand) name.
• The official name of the drug is the generic
  name.
• The chemical name describes the molecular
  structure of the drug.
• The proprietary (brand) name is assigned by the
  drug manufacturer.

Prozac Fluoxetine HCl N-Methyl-3-phenyl-propylamin
e
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Examples of Generic, Chemical, and Brand Names
Generic Name Chemical Name Brand Name
Fluoxetine HCl N-methyl-3-phenyl-propylamine Prozac
Acetaminophen 4-Hydroxyacetanilide Tylenol
Ibuprofen 2-p-Isobutylphenyl-propionic acid Motrin
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Comparison Between Brand Name Drugs and Generic
Drugs

• The inventor of a new drug may apply for patent
  protection. If awarded, the manufacturer is
  given up to 20 years exclusive rights to
  manufacture and distribute the new drug.
• Once the drug is off the patent, other drug
  companies may manufacture a generic equivalent.
• Generic drugs contain the same active ingredients
  as the original manufacturers drug, in the same
  strength. However, generic drugs may contain
  different inactive ingredients, which may affect
  how much of the drug is available to the body.

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Comprehensive Drug Abuse Prevention and Control
Act (1970)

• Also known as the Controlled Substance Act.
• The Act regulates drugs that have a history for
  abuse.
• Controlled Substances are placed in a schedule
  or category according to their abuse potential
  and effects if abused.
• The schedules are determined by Federal and
  State laws.

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Controlled Substance Schedule
Schedule Classification Examples
C-I These drugs have a high potential for abuse. No medical uses for treatment Ecstasy, heroin, LSD, marijuana, PCP
C-II High potential for abuse. Has accepted medical use for treatment Morphine, oxycodone, methamphetamine
C-III Less abuse potential than C-II drugs. Accepted medical use. Anabolic Steroids, Hydrocodone
C-IV Less abuse potential than C-III drugs. Accepted medical use. Valium, Xanex, Darvon, Phentermine
C-V Less abuse potential than C-IV drugs. Accepted medical use. Cough medicines with Codeine
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FDA Pregnancy Safety Classification

• Class A known to be safe (Vitamins)
• Class B probably safe (Penicillin,
  Erythromycin)
• Class C use cautiously if benefits outweigh
  risks (heparin, anti-depressants)
• Class D known to cause fetal problems. Use
  only if untreated maternal disease is harmful to
  fetus (Lithium, Phenobarbitol, Amiodorone)
• Class E contradicted in pregnancy (Coumadin,
  Methotrexate)

Thalidomide Baby
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Drug Dosage Forms and Delivery Systems

• Drugs are created for delivery by mouth (oral),
  injection (parenteral), inhalation, or topical
  application to the skin or mucous membranes.
• Oral administration is safe, easy, and generally
  more economical than parenteral administration.
• Common oral formulations include tablets,
  capsules, solutions, emulsions, syrups,
  suspensions, and elixirs.

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Tablets

• Tablets are solid forms containing one or more
  active ingredients plus binders, which allow the
  drug to take a shape.
• Delayed action tablets slow the release of the
  drug to avoid destruction of the drug in the
  stomach.
• Enteric coated tablets have an acid-resistant
  coating to prevent dissolving in the stomach.
  Release contents into small intestine.
• Sustained release (timed release) deliver their
  contents over time (ex 24 hours). Crushing may
  cause contents to be released immediately.
• Chewable tablets for people who have difficulty
  swallowing pills. Used frequently with children.
• Sublingual tablets dissolved in the mouth,
  where many blood vessels are located. Gets into
  bloodstream fast and by-passes stomach.

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Capsules

• Capsules are solid dosage forms containing one or
  more active ingredients plus binders and fillers.
• Formulated to deliver their ingredients
  immediately or over time.

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Oral Liquids

• Oral Liquids are easy to swallow and work more
  rapidly than tablets or capsules.
• Suspensions contain small drug particles
  suspended in a liquid.
• Solutions drug particles are completely
  dissolved in the liquid.
• Syrups contain a high concentration of sucrose
  or other sugars.
• Elixirs contain between 5 and 40 alcohol.
• Tinctures contain between 17 and 80 alcohol.
• Emulsions similar to suspensions. May be
  dispersed in oil or water.

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Topical Administration

• Ointments semisolid preparations containing
  petroleum or another base. Form a protective
  barrier between the skin and harmful substances.
• Creams semisolid emulsions applied directly
  onto the skin.
• Suppositories solid or semisolid dosage forms
  intended to be inserted into a body orifice.
  Melt at body temperature, dispersing the medicine

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Transdermal Drug Delivery System

• Transdermal patches are controlled-released
  devices that deliver medication across skin
  membranes into the general circulation. They
  produce both local and systemic effects.
• Examples
• Nitroglycerin for angina
• Estrogen for menopause
• Fentanyl for pain

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Routes of Administration of Drugs

• By Mouth, Oral (PO) The major benefit of oral
  administration is the convenience to the patient.
  
• -Oral medications are systemic (work
  throughout the body)
• -Safer, because they take time to work and
  therefore an antidote can be given if overdosed.
• -However, these drugs do not work as quickly

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Routes of Administration of Drugs

• Sublingual and Buccal Agents (SL, Buccal) Few
  medications are administered in this form, but
  the medications administered in this manner are
  very effective. These medicines by-pass the
  digestive system, and are absorbed directly into
  the blooodstream.
• -Nitroglycerin is given sublingually for
  Angina.
• -Parcopa is given sublingually for
  Parkinsons

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Routes of Administration of Drugs

• Rectal Agent (PR) may be used in patients who
  are vomiting and cannot take oral medications.
  Suppositories or rectal creams may be used.
  These agents usually work locally, not
  systemically.
• -Suppositories for motion sickness, nausea
  (systemic effects)
• -Laxatives (work locally)

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Routes of Administration of Drugs

• Topical Agents topical agents can have systemic
  or local effects. They are popular due to the
  ease of application, and the rapid effect
  produced.
• -Examples include Bacitracin (antibiotics),
  Benadryl (antihistamine), Estrogen patches
  (hormonal), some blood pressure medications, and
  smoking cessation agents.
• -May cause skin reactions.
• -More expensive than oral medications.

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Routes of Administration of Drugs

• Parenteral (Intravenous, Intramuscular,
  Subcutaneous) given outside the intestines.
• -Benefits speed of action, not inactivated
  by stomach acids, not harmful to the stomach.
• -Disadvantages increased risk of infection,
  difficult to reverse toxic or allergic effects,
  more expensive, must be given by trained medical
  personnel.
• -Examples Insulin, Heparin (blood thinner),
  IV antibiotics, chemotherapy.

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Routes of Administration of Drugs

• Inhalants primarily used in patients with
  respiratory (lung) diseases. Also used to
  anesthetize patients prior to surgical
  procedures.
• -Benefits ease of use, quick onset of
  action
• -Disadvantages must be used properly to be
  effective.
• -Examples Albuterol Inhaler
  (Bronchodilator for Asthma), Nitrous Gas
  (anesthesia for dental/surgical procedures).

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Pharmacokinetics
Once a drug is administered to a patient, the
drug then undergoes the 4 phases of
Pharmacokinetics. These phases include
-Drug absorption into the bloodstream -Drug
distribution to their site of action before they
produce their effects. -Drug
metabolism by the body -Drug elimination
from the body These pharmacokinetic phases
control the intensity of a drugs effect and the
duration of the drug action.
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Pharmacokinetics

• The absorption of a drug is dependent upon
• -the tissue thickness
• -blood flow to the area
• -drug concentration
• -surface area (ex microvilli of the small
  intestines
• -lipid solubility of the drug, allowing it to
  pass through the cell membrane

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Pharmacokinetics

• Drug distribution is the process of movement of
  the drug from the circulatory system, across
  barrier membranes, to the site of drug action.
• The quantity (volume) of drug distributed is
  influenced by
• -the properties of the drug
• -the extent of drug binding to blood proteins
• -the blood supply to the region
• -the ability of the drug to cross natural body
  barriers (ex blood-brain barrier, blood-placenta
  barrier)

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Pharmacokinetics

• Metabolism most drugs are transformed by enzymes
  (usually in the liver) to a metabolite that is
  less active than the original drug.
• Biotransformation is the process of drug
  metabolism in the body that transforms a drug to
  a more active, equally active, or inactive
  metabolite.
• The main site of biotransformation occurs in the
  liver.

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Pharmacokinetics

• Factors Influencing Metabolism
• 1. Liver Function the liver is the primary
  site for metabolism. If the liver function
  decreases, metabolism decreases. In cases of
  liver disease, drug doses should often be reduced
  because less drug is capable of being broken-down
  by the liver.

Jaundice notice yellow sclera
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Pharmacokinetics

• Factors Influencing Metabolism
• 2. Effects of Disease Diseases like hepatitis
  decrease the metabolic capacity of the liver.
  Lung disease and Kidney disease can also reduce
  the bodys ability to metabolize drugs.
• 3. Effects of Age Metabolism in the liver is
  decreased in both the elderly and in infants.
  Therefore, infants and the elderly require lower
  doses of drug to produce therapeutic effects.

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Pharmacokinetics

• Factors Influencing Metabolism
• 4. Interactions of two or more drugs
  Administration of two or more drugs that both use
  the same metabolic pathways can alter the
  metabolism of eachother.
• -Ex Phenytoin is a drug used to treat
  epilepsy. Phenytoin can increase the metabolism
  of Warfarin, a drug used to decrease blood
  clotting. This will make Warfarin less
  effective.
• -Ex St. Johns Wart, an herb, can
  increase the metabolism of birth control pills,
  causing a woman to possibly get pregnant while
  on the pill.

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Pharmacokinetics

• Elimination is the final pharmacokinetic phase.
  Elimination results in the removal of the drug
  from the body, and discontinuation of drug
  action.

The three major routes of drug elimination are
-kidney -lung -bowel
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Pharmacokinetics

• Elimination Half-life (T1/2) the time it takes
  for 50 of the drug to be cleared (eliminated)
  from the bloodstream.
• It takes approximately 8 half-lives to entirely
  eliminate a drug from the body.
• Every drug has its own unique half-life. It is
  important to know a drugs half-life, because it
  is an indicator as to how long a drug will
  produce effects in the body.

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Pharmacokinetics

• Bioavailability the extent to which an
  administered amount of drug reaches the site of
  action and is available to produce drug effects.
• Bioavailability is influenced by drug absorption
  and distribution to the site of action.
• Bioequivalent drugs achieve the same maximum
  blood concentration, in the same period of time.

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Pharmacokinetics
The area under the curve (shaded area) is the
measure of a drugs bioavailability
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Although similar and related, equal
bioavailability (F) does not guarantee
bioequivalence.
Two dose forms of the same drug are depicted.
These two dose forms have equal bioavailability
and they are bioequivalent.
Two dose forms of the same drug are depicted.
These two dose forms have equal bioavailability
but they are NOT bioequivalent.
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Pharmacodynamics

• Pharmacodynamics is the study of drugs and
  their action on the living organism.
• -looks at how the body responds to drugs
  that are administered.
• Mechanism of Action describes how the drug
  produces its effects.

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Pharmacodynamics

• Drug-receptor theory drugs interact or bind
  with targeted cells in the body to produce
  pharmacologic action.
• The location of the drug-cell binding is called
  the receptor site.

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Pharmacodynamics

• Drug-receptor binding is similar to the action of
  a lock and key. The drug is the key, and the
  receptor is the lock.
• The more similar the drug is to the shape of the
  receptor site, the greater the affinity
  (attraction) that the receptor site has for the
  drug.

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Pharmacodynamics

• Types of Drug-Receptor Interactions
• Drugs are described as agonists, partial
  agonists, competitive antagonists, and
  non-competitive antagonists based on their effect
  at the receptor site.

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Pharmacodynamics

• Agonist is a drug that binds to and activates
  the receptor site, eliciting a response.
• Partial Agonist is a drug that binds to a
  receptor, but produces a reduced (diminished)
  response, compared with that of an agonist.

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Pharmacodynamics

• Antagonist binds to the receptor site and does
  not produce an action. The drug prevents the
  binding of agonists.
• Competitive Antagonist drug competes with the
  agonist for the binding site of the receptor. If
  it binds, there is no response.
• Noncompetitive Antagonist drug binds with an
  alternative site on the same receptor (not at the
  same site as the agonist), inactivating the
  receptor site.

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Pharmacodynamics

• Efficacy describes the maximum response
  produced by a drug. It is a measure of a drugs
  effectiveness.
• -Agonists produce the maximum drug response.

Which drug has higher efficacy, Drug A or Drug B?
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Pharmacodynamics

• Potency Efficacy and potency are related.
  Drugs that have high efficacy at low dose are
  very potent.
• -Drugs that are very potent require only a
  small dose to produce a maximum drug effect.

Which drug is more potent, Drug A or Drug B?