Pharmacology For The Pharmacology For The Physical Therapy ClinicianPhysical Therapy Clinician

Basic Principles

Pharmacology can be broadly defined as the science dealing with interactions between living systems and molecules

Throughout the ages, drugs have been produced using natural plant and animal products by native people. This practice has been part of every culture and society in every corner of the world.

Some Examples…….Some Examples…….

Hollyhock Tea - made from the leaf and root of the Hollyhock plant.

Used For : sore throats, duodenal ulcers, GI tract infections

Echinacea - the roots, seed heads & petals can be used to make an Echinacea tincture and salve

Uses : stimulates immune defense, speeds healing, limits edema & swelling.

Jojoba - the beans and the leaves are used to make a variety of oil, soap & shampoo products.

Uses : Soaps, shampoos, oil lubricants - often used for a remedy for asthma, dandruff, and as an anti-inflammatory

Advantages Of Synthetic Advantages Of Synthetic DrugsDrugs

Improved purityImproved action due to an

altered chemical structureLonger biological half-lifeImproved fat solubility

Greater drug concentrationLonger shelf lifePreserve the environmentLess costly to produce

Drug Interactions With A Drug Interactions With A Biological SystemBiological System

Pharmacodynamic InteractionsPharmacokinetic Interactions

Pharmacodyamic Interactions

The mechanism of action - the the drug works on the body

Pharmacokinetic Interactions

The way in which the body absorbs, distributes and eliminates the drug

Drug NomenclatureDrug NomenclatureChemical Name

The chemical name describes the chemical structure of a drug.

Used by pharmacists & researchers all over the world

Examples…….Examples…….

Tylenol (Acetaminophen)

N-acetyl-para-aminophenol

Phenobarbitol

5,5-phenylethylbarbituric acid

Generic Name

It is generally derived from the chemical name but is shorter

It is also known as the official or non-proprietary name

Examples…….Examples…….

Dextromethorphan

Dextromethorphan is the generic name for the drug with the chemical name of :

d-3-methoxy-N-methylmorphinan

Dantrolene Sodium

Dantrolene is the generic name for the drug with the chemical name of :

1-[[[5-(4-nitrophenol)-2-furanyl]methylene]amino]-2-4-

imidazolidinedione

Trade Name

This is the name the manufacturer gives to the drug that distinguishes it from the same drug made by other drug companies

Examples…….Examples…….

Flecanide Acetate is the generic name for a drug with the trade name of :

Tambocor

Digoxin is the generic name for the drug with the trade name of :

Lanoxin

Bepridil HCl is the generic name for a drug with the trade name of :

Vascor

The FDA catalogs the drug by its generic name

The manufacturer catalogs the drug by its trade name

The research pharmaceutical chemists know the drug by its chemical name

Routes of AdministrationRoutes of Administration

Enteral RoutesParenteral Routes

Enteral RoutesEnteral Routes

Drugs that are administered through the alimentary canal via the sublingual, oral or rectal routes

Advantages Of The Enteral Advantages Of The Enteral RouteRoute

It is not invasiveEase of drug administrationThe mouth and the GI tract have a rich blood supply for pancorporeal dispersal of the medication

The enteral route avoids large fluctuations in drug delivery

Patients are familiar with the oral delivery route

The GI tract has a massive surface area for absorption

Disadvantages of the Disadvantages of the Enteral RouteEnteral Route

Drugs must be lipid solubleDrugs can be irritating to the mucosa of the mouth and the gut

First Pass EffectThe presence of diseases like Crohn’s Disease is a problem

pH of the GI tract

Parenteral RoutesParenteral Routes

Drugs administered through non-alimentary pathways such as : inhalation, intravenous, intra-arterial, subcutaneous, intramuscular, intrathecal, ocular, topical, and transdermal

Advantages of Parenteral Advantages of Parenteral RoutesRoutes

Fast delivery of the medications (IV, inhalation, and intra-arterial routes)

Efficient maintenance of therapeutic ranges (IV and intra-arterial routes)

Ease of self administration (topical, inhalation, rectal, & subcutaneous routes)

Can give large quantities of medication (IV, intra-arterial)

First Pass EffectFirst Pass Effect

When an enterally administered drug passes for the first time from the gut into the hepatic portal system and enters the liver, it can undergo First Pass Effect

During First Pass Effect, a certain percentage of the drug is changed from the original mother compound into some intermediate metabolite. All of the drug then passes out into the systemic circulation as 1) the intact drug plus its 2) changed intermediates.

For some drugs, like sublingual nitroglycerin, if it were swallowed, it would be totally inactivated by the liver. So, its first pass effect is complete or 100%

For other drugs that are not as easily cleaved, the First Pass Effect might only be 10%. This means that 90% of the mother compound enters the systemic circulation with only 10% that has been changed into an intermediate.

The intermediate compounds after First Pass Effect may be biologically inactive or they might be extremely active in the body. Many cancer drugs are designed to have intermediates that are just as biologically active against the tumor as the mother compound.

Some medications are designed to be inactive in the pill form. Once these medications pass into the liver (First Pass Effect) they are cleaved into their biologically active intermediate forms. In the pill form, these drugs are called Pre-Drugs.

BioavailabilityBioavailability

Bioavailability is defined as the amount of drug that actually makes it to the intended downstream target. Bioavailability is influenced by a number of factors.

Factors Influencing Factors Influencing BioavailabilityBioavailability

First Pass EffectRoute of administrationLipid solubility of the drugBlood flow at the administration

site

Blood flow at the intended target organ or site

Absorptivity of the gutHow easily the drug is changed or

metabolized

Drug EliminationDrug Elimination

The liver and the kidneys are the major detoxification organs in the body

The blood, muscles and the lungs are secondary areas where detoxification occurs

BiotransformationBiotransformation

The body detoxifies itself through inducing chemical changes in the drugs that have been ingested

The body biochemically alters the drugs through biochemical processes like hydrolysis, oxidation, reduction, conjugation

Enzyme InductionEnzyme Induction

Long term use of medications stimulates enzymatic pathways in the body to more vigorously breakdown the medication into intermediates that can be easily excreted in the feces or urine

There are many stimuli that cause enzyme induction to be turned on such as :

tobacco usealcohol usedrug abuseenvironmental wastes and toxins

Why Do Humans Respond Why Do Humans Respond Differently To Medications ?Differently To Medications ?

Genetic Factors Diet, Age, & Adiposity Alcohol & Tobacco Use Disease State