Download L1: Intro to Pharm- Objectives Describe what is meant by a drug`s

L1: Intro to Pharm- Objectives
1. Describe what is meant by a drug’s “Mechanism of Action”.
Mechanism of Action is how a drug works. Includes the site where the drug acts and the
mechanism by which it produces its effects (desired effects)
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Propranolol blocks -adrenergic receptors in heart myocardium thereby reducing
sympathetic-mediated contractile force (antihypertensive agent)
2. Contrast a “side-effect” and a “contraindication”.
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Side effects (can be adverse, but not necessarily): undesired effects of the drug
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constriction, which could be fatal in asthmatics or in pts with other obstructive lung disorders
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Contraindications: 1) Conditions that preclude safe use of the drug (eg. Propranolol
contraindicated in asthmatics), 2) Co-administration with other drugs may produce
undesirable/altered effects
3. Differentiate between “agonists” and “antagonists”.
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Agonist: drug that binds to receptor and stimulates cellular activity
Antagonist: drug that binds to receptor and inhibits the action of agonists
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Drugs
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Endogenous agents
4. Give two targets of drug action other than receptors or ion channels.
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Protein targets for drug binding include:
Receptors, Enzymes, Carrier molecules, Ion channels, Other: structural proteins (colchicine binds
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5.
Drugs can bind to plasma proteins, but not site of action (transport)
Receptors are integral to the system of chemical communication that all multicellular
organisms use to coordinate the activities of their cells & organs. (typically on outside of
lipid bilayer
Differentiate among “chemical”, “pharmacological”, and “physiological” antagonists
 Drugs not acting through receptors (directly):
-chemical antagonists
Protamine binds stoichiometrically to heparin anticoagulants
-physiological antagonists (one drug inhibits another through a completely different
route)
Adrenergic beta blockers for thyroid hormone-induced tachycardia
-osmotic agents
Mannitol for subarachnoid hemmorhage
-DNA
Cancer chemotherapeutic agents
6. Differentiate between pharmacodynamics and pharmacokinetics.
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Pharmacodynamic: “actions of drug on the body”
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Pharmacokinetic: “actions of the body on the drug”
7. Definitions

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Drug: any substance that brings about a change in biologic function through its chemical
action.
Receptor: specific regulatory molecule in the biologic system where drug interacts.
-activates or inhibits normal body processes.

Therapeutic benefit derived by acting on processes:
1.within the patient
2.directed at parasites infecting the patient.
8. The nature of drugs

Drugs / Agents / Ligands
-Endogenous (eg, hormones)
-Exogenous: xenobiotics (Gr.: xenos ‘stranger’).
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Poisons are drugs
-Inorganic poisons: Pb, Ar, Hg
-Toxins: atropine
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Physical Characteristics
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Drug size: varies from very small (Li = MW 7) to very large (eg, alteplase [t-PA] = MW
59,050). Vast majority have MW between 100 & 1,000.
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Lower limit allows specificity of drug action
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Upper limit determines extent of movement within the body
Drug shape is all important:
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Fits with receptor like lock & key
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Only a few receptor types are likely to provide such a precise fit for a particular
drug structure.
Drugs have chirality (stereochemistry)
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Left (S) & right (R) handedness, enantiomers, isomers
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Enzymes are usually stereoselective  difference in duration of action
Most drugs are marketed as racemic mixtures  patients are receiving drug doses of
which 50% or more are either inactive or potentially harmful
•
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pH: Many drugs are weak acids or bases, each having unique pK. Body compartment pH
affects ionization of drugs.
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Warfarin given as racemic mixture (S enantiomer 4X more potent than R:
interaction with binding site on Vit. K epoxide reductase)
Movement of drug between compartments determined by degree of ionization.
Partition Coefficients: blood/gas, blood/tissue
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Also influence movement of drug between body compartments
9. Drug properties to know
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Name and class: GENERIC vs. brand name (proprietary name)
Eg. Fluoxetine (PROZAC), Anti-depressant
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Indication: the basis for the initiation of treatment
Fluoxetine is used for Major Depressive Disorder.
- FDA establishes “approved use of drug”
- “off label indication”
10. Drug Classification
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Pharmacotherapeutic: refers to the clinical condition for which the drug is used
-Imprecise: antibacterial, antiviral
Subclassification adds precision
-Based on type of virus, bacteria, etc
-Precise: antitubercular (Mycobacterium tuberculi)
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Precision is only possible if underlying pathology of disease is known
Pharmacologic: based on a drug’s mechanism of action, including action of the system in
response to the drug (inhibition, excitation, etc.)
-Includes pharmacotherapeutic  molecular  cellular  tissue  systemic
-Ex.: Propranolol: Antihypertensive  -adrenergic receptor blocker  prevents receptor-mediated stimulation of adenylyl cyclase  reduces contractile strength of
cardiac muscle cell  tissue also  ’s cardiac output & ’s BP