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PHA 053 SAS #1 Basic Principles of Pharmacology Cheat Sheet (DRAFT) by

Basic and Clinical Pharmacology — Bertram Katzung 14th Edition (Chapter 1, Chapter 3, Chapter 4)

This is a draft cheat sheet. It is a work in progress and is not finished yet.


is the study of substances that interact with living systems through chemical processes, especially by binding to regulatory molecules and activating or inhibiting normal body processes.


A branch of pharma­cology which deals with the undesi­rable effects of chemicals on living systems, from individual cells to complex ecosys­tems.


Is defined as the science of substances used to prevent, diagnose, and treat disease.

Reasons for different Routes of Admini­str­ation:

• For conven­ience – oral drugs
• To maximize concen­tration at the site of action and minimize it elsewhere (topical)
• To prolong the duration of drug absorption (trans­dermal)
• To avoid the first pass effect

Weak Acid and Weak Base

Weak acid - is a neutral molecule that can reversibly dissociate into an anion and a proton
Weak base - a neutral molecule that can form a cation by combining with a proton.
Applic­ation of the principle:
- Acidic drugs are best absorbed from acidic enviro­nments
- Basic drugs are best absorbed from basic enviro­nments

Thus, weak acids are usually excreted faster in alkaline urine; weak bases are usually excreted faster in acidic urine.

Table 1 - 4


The goal of therap­eutics is to achieve a desired beneficial effect with minimal adverse effects.
the actions of the body on the drug.
determine how rapidly and for how long the drug will appear at the target organ.
Pharma­cok­inetics deals with the dose- concen­tration part.
this govern the Absorp­tion, Distri­bution, and Elimin­ation of drugs


PRODRUG - an inactive precursor chemical that is readily absorbed and distri­buted is admini­stered and then converted to the active drug by biologic processes – inside the body.
FREE DRUG - exerts a biologic effect
BOUND DRUG - stays in the vascular space and is not metabo­lized or elimin­ated.
PERMEATION - is the movement of drug molecules into and within the biologic enviro­nment.


Drug - any substance that brings about a change in biologic function through its chemical actions.
the drug molecule interacts as an agonist (activ­ator) or antagonist (inhib­itor) with a specific target molecule that plays a regulatory role in the biologic system.
Drugs maybe synthe­sized within the body (eg. Hormones) or maybe chemicals not synthe­sized in the body, ie. Xenobi­otics (xenos – “stran­ger”)
Poisons - are drugs that have almost exclus­ively harmful effects. (Paracelsus – famously stated “the dose makes the poison” --- any substance can be harmful if taken in the wrong dosage)
Toxins - are defined as poisons of biologic origin, synthe­sized by plants or animals


Phase 1 Reactions
usually convert the parent drug to a more polar metabolite by introd­ucing or unmasking a functional group (–OH, –NH2, –SH).
• If phase I metabo­lites are suffic­iently polar, they may be readily excreted.
- involves oxidation, reduction, hydrolysis
- alter chemical reactivity and increase aqueous solubility
PHASE II reactions
- involves conjug­ation
this reaction further increases the solubi­lity, promoting elimin­ation

Plasma Protein Binding:

if a drug is displaced from plasma proteins it would increase the unbound drug concen­tration and increase the drug effect and, perhaps, produce toxicity.
When the amount of unbound drug in plasma increases, the rate of elimin­ation will increase and after four half-lives the unbound concen­tration will return to its previous steady state value.


A. Types of Drug-R­eceptor Intera­ctions
AGONIST – drugs bind to and activate the receptor in some fashion, which directly or indirectly brings about the effect.
ANTAGONIST – by binding to a receptor, prevent binding by other molecules.
Partial agonist – bind to the same receptors and activate them in the same way but do not evoke as great a response, no matter how high the concen­tra­tion.
Inverse agonist –is a ligand that binds to the same recept­or-­binding site as an agonist and not only antago­nizes the effects of an agonist but exerts the opposite effect by suppre­ssing sponta­neous receptor signaling (when present).
- Most drugs must bind to a receptor to bring about an effect.

The Physical Nature of Drugs

To interact chemically with its receptor, drug molecule must have the:
Approp­riate Size
Electrical Charge
Atomic compos­ition
A useful drug must have the necessary properties to be transp­orted from its site of admini­str­ation to its site of action.

A practical drug should be inacti­vated or excreted from the body at a reasonable rate so that its actions will be of approp­riate duration.


PHARMA­COD­YNAMICS – the actions of the drug on the body. These determine the group in which the drug is classified
PHARMA­COK­INETICS – the actions of the body on the drug. Govern the Absorp­tion, Distri­bution, and Elimin­ation of drugs


VOLUME of DISTRI­BUTION (V) - the measure of the apparent space in the body available to contain the drug. Relates the amount of drug in the body to the concen­tration of drug (C) in blood or plasma.
CLEARANCE - the measure of the ability of the body to eliminate the drug. The factor that predicts the rate of elimin­ation in relation to the drug concen­tra­tion.
- The two major sites of drug elimin­ation are the kidneys and the liver.
- Clearance of unchanged drug in the urine represents renal clearance.
- Within the liver, drug elimin­ation occurs via biotra­nsf­orm­ation


The fraction of unchanged drug reaching the systemic circul­ation following admini­str­ation by any route.

Pharma­cok­inetic Processes

Applies to drugs given orally
– Release of drug from pill, tablet, capsule
– Dissolving of active drug in GI fluids
Movement from admini­str­ation site into circul­ation
The transport of a drug in the body by the bloods­tream to its site of action.
The biologic transf­orm­ation of a drug into an inactive metabo­lite, a more soluble compound, or a more potent metabo­lite.
- is the process by which a drug or metabolite is eliminated from the body.
Rate of Absorption
- a constant fraction of drug is absorbed.
- a constant amount of drug is absorbed.

The blood brain barrier consists of cell tightly packed around the capill­aries of the CNS.

KIDNEY = most important organ for excretion of drugs.
= primary site

Liver is the principal organ of drug metabo­lism.

The 3 Major Types of Chemical forces or Bonds

COVALENT bonds – are very strong and in many cases not reversible under biologic condit­ions.
ELECTR­OSTATIC bonds – more common but are weaker than covalent bonds.
HYDROP­HOBIC bonds – are usually quite weak and are important in the intera­ctions of highly lipid soluble drugs.

Factors Influe­ncing Absorption and Bioava­ila­bility

Aqueous diffusion of drug molecules is usually driven by the concen­tration gradient of the permeating drug, a downhill movement described by Frick’s law.
Lipid diffusion - is the most important limiting factor for drug permeation because of the large number of lipid barriers that separate the compar­tments of the body.
Special Carriers – Special carrier molecules exist for certain substances that are important for cell function and too large or too insoluble in lipid to diffuse passively through membranes.

Endocy­tosis and Exocyt­osis:

ENDOCY­TOSIS - is the process by which the substance is bound at a cell-s­urface receptor, engulfed by the cell membrane, and carried into the cell by pinching off of the newly formed vesicle inside the membrane.
EXOCYTOSIS - the reverse process. Is respon­sible for the secretion of many substances from cells.
For a drug to cross the lipid membrane easily / readily must have the ff. factors:
– Lipid soluble
– Uncharged
– Non polar
– Small in size
– Non ionized


Immediate Effects
drug effects are directly related to plasma concen­tra­tions.
Delayed Effects
Changes in drug effects are often delayed in relation to changes in plasma concen­tra­tion.
Cumulative Effects
It is the accumu­lation of aminog­lyc­oside in the renal cortex that is thought to cause renal damage.

Biological Half-life (t 1/2)

is the time required to change the amount of drug in the body by one-half during elimin­ation.
the most useful in designing drug dosage regimens.
it indicates the time required to attain 50% of steady state—or to decay 50% from steady­-state conditions

Drug Accumu­lation

With repeating drug doses, the drug will accumulate in the body until dosing ceases.
Accumu­lation: inversely propor­tional to the fraction of the dose lost in each dosing interval.
The accumu­lation factor predicts the ratio of the steady­-state concen­tration to that seen at the same time following the first dose.

Hepatic ‘First­-Pass’ Metabolism

• Affects orally admini­stered drugs
• Drug absorbed into portal circul­ation, must pass through liver to reach systemic circul­ation
• May reduce availa­bility of drug

Designing a Rational Dosage Regimen

– Drugs are admini­stered to maintain a steady state concen­tration in the body. (just enough drug is given in each dose to replace the drug eliminated since the preceding dose)
is the most important pharma­cok­inetic term to be considered in defining a rational steady- state drug dosage regimen. – At steady state, the dosing rate (“rate in”) must equal the rate of elimin­ation (“rate out”).
– Promptly raises the concen­tration of drug in plasma to the target concen­tra­tion.

Enzyme Induction & Inhibition

– Enhance the rate of drug`s synthesis or reducing its rate of degrad­ation.
– Induction results in an accele­ration of substrate metabolism and usually in a decrease in the pharma­cologic action of the inducer and also of coadmi­nis­tered drugs.
– Certain drug substrates inhibit cytochrome P450 enzyme activity.
– Reduce the metabolism of the endogenous substrates or other coadmi­nis­tered drugs.