Chapter 1
Pharmacology: the science of drug action
• Pharmacology studies the actions of drugs and their e ects on living organisms.
• Plants have been a signi cant part of ancient human life, with writings from 1500 BCE
describing plant-based medicines in Egypt and India.
• The Ebers Papyrus describes over 700 remedies for various ailments, including crocodile
bites, baldness, constipation, headache, and heart disease.
• Modern drugs like castor oil and opium are also mentioned.
• The Chinese have a long tradition of using herbal remedies, with estimates suggesting 80%
of people in developing countries are completely dependent on herbs or plant-derived
medicinals.
• In the United States, modern herbal medicines and natural products represented half of the
top 20 drugs on the market in 1999.
• Despite limited clinical support, many Americans are enamored with herbal remedies due to
their perceived "natural" nature.
• Neuropharmacology and psychopharmacology are two specialized areas of pharmacology,
focusing on drug-induced changes in the nervous system and mood, thinking, and behavior.
• Drug action refers to speci c molecular changes produced by a drug when it binds to a
speci c target site or receptor, leading to alterations in physiological or psychological
functions.
Understanding Drug E ects and Their Characteristics
Drug E ects:
• Drugs act at various target sites, resulting in multiple e ects.
• Some are therapeutic e ects, causing desired physical or behavioral changes.
• Other e ects are side e ects, ranging from mildly annoying to distressing and dangerous.
• Examples include amphetamine-like drugs producing alertness, insomnia, increased heart
rate, and decreased appetite.
• Drugs can also be used as a diet control in weight-reduction programs, causing insomnia and
hyperactivity.
Drug Characteristics:
• There are no "good" or "bad" drugs; all drugs are chemicals.
• The way a drug is procured and used determines its character.
• Some drugs, like alcohol, are considered "good" under certain conditions but can lead to
addiction when misused.
• Many "good" prescription drugs are illicitly acquired or misused, leading to "bad" outcomes.
Speci c and Nonspeci c Drug E ects:
• Speci c drug e ects are based on physical and biochemical interactions with a target site in
living tissue.
• Nonspeci c drug e ects are in uenced by an individual's background, mood, expectations,
perceptions, and attitude towards the drug-administering person.
Placebo e ect
• Plaque is not a "fake" pill but a pharmacologically inert compound with therapeutic and side
e ects.
• Belief in a drug can produce physiological e ects, including measurable changes like altered
gastric acid secretion, blood vessel dilation, and hormonal changes.
• A study showed that 70% of patients found signi cant relief from a placebo, while only 25%
were helped by the "drug."
Page 1 of 17
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, • The e ectiveness of a sugar pill depends on the ritual of the therapeutic treatment, which can
have both neurobiological and behavioral e ects.
• There is increasing interest in understanding the mechanism responsible for the placebo
e ect to enhance the therapeutic e ectiveness of drug treatments.
• Placebo e ects may be explained by Pavlovian conditioning, where symptom improvement is
associated with speci c characteristics of a medication, a recommending clinician, or aspects
of the medical facility.
• Deception is not necessary as patients bene t even if they are told the medication is a
placebo.
Placebo E ect and Its Contributions
• The placebo e ect may be in uenced by conscious, explicit expectation of outcomes.
• Individuals who anticipate relief may show an enhanced placebo response.
• Placebo-induced neurobiological e ects within the brain are signi cant.
• Subjects who anticipate pain relief show reduced neural activity in pain-related brain regions.
• Other factors may contribute to the placebo e ect, including social learning, anticipating a
positive outcome, and genetic variants.
• Negative expectations can increase anxiety and in uence treatment outcomes.
• The nocebo e ect, where expecting treatment failure and verbal suggestions of negative
outcomes increase anxiety and neural mechanisms, can be reduced by antianxiety drug
treatment.
• Nocebos are important to study as warnings about potential side e ects can lead to greater
side-e ect occurrence.
• The placebo is essential in pharmacology to eliminate the in uence of expectation on the
experiment’s participants.
• Some researchers use an “active” placebo or leave the placebo group untreated if an
e ective agent is available.
Double-Blind Experiments in Clinical Research
• Nonspeci c factors and variable placebo responders contribute to double-blind experiments.
• No participant or observer knows treatment received.
• Precautions prevent bias in treatment results.
• Brown (1998) and Louhiala (2009) provide more on placebo use in clinical research and
therapeutics.
Pharmacokinetic factors determine drug action
Drug Action Factors
• Chemical structure of a drug determines action.
• Dosage and bioavailability are key contributors.
• Dynamic factors contribute to bioavailability.
• These factors form the pharmacokinetic component of drug action.
Page 2 of 17
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, Methods of drug administration in uence the onset of drug action
- The route of administration of a drug determines how much and how quickly its e ect occurs
- Systemic routes of administration distribute drugs throughout the entire body, while enteral
methods use the gastrointestinal tract
- Oral administration is the most commonly used route for drugs as it is safe, self-administered,
and economical
- Drugs must dissolve in stomach uids and pass through the stomach or intestine wall to
reach blood capillaries to be e ective
- Absorption is the movement of the drug from the site of administration to the blood
circulation
- Factors such as food in the stomach, physical activity, and rst-pass metabolism can
in uence the rate of absorption
- Some therapeutic drugs taken orally may undergo extensive metabolism, reducing their
bioavailability
- Drug plasma levels are more irregular and unpredictable and rise more slowly than those
produced by other methods of
administration due to these factors.
Page 3 of 17
fl ff fl fl fi ff
Pharmacology: the science of drug action
• Pharmacology studies the actions of drugs and their e ects on living organisms.
• Plants have been a signi cant part of ancient human life, with writings from 1500 BCE
describing plant-based medicines in Egypt and India.
• The Ebers Papyrus describes over 700 remedies for various ailments, including crocodile
bites, baldness, constipation, headache, and heart disease.
• Modern drugs like castor oil and opium are also mentioned.
• The Chinese have a long tradition of using herbal remedies, with estimates suggesting 80%
of people in developing countries are completely dependent on herbs or plant-derived
medicinals.
• In the United States, modern herbal medicines and natural products represented half of the
top 20 drugs on the market in 1999.
• Despite limited clinical support, many Americans are enamored with herbal remedies due to
their perceived "natural" nature.
• Neuropharmacology and psychopharmacology are two specialized areas of pharmacology,
focusing on drug-induced changes in the nervous system and mood, thinking, and behavior.
• Drug action refers to speci c molecular changes produced by a drug when it binds to a
speci c target site or receptor, leading to alterations in physiological or psychological
functions.
Understanding Drug E ects and Their Characteristics
Drug E ects:
• Drugs act at various target sites, resulting in multiple e ects.
• Some are therapeutic e ects, causing desired physical or behavioral changes.
• Other e ects are side e ects, ranging from mildly annoying to distressing and dangerous.
• Examples include amphetamine-like drugs producing alertness, insomnia, increased heart
rate, and decreased appetite.
• Drugs can also be used as a diet control in weight-reduction programs, causing insomnia and
hyperactivity.
Drug Characteristics:
• There are no "good" or "bad" drugs; all drugs are chemicals.
• The way a drug is procured and used determines its character.
• Some drugs, like alcohol, are considered "good" under certain conditions but can lead to
addiction when misused.
• Many "good" prescription drugs are illicitly acquired or misused, leading to "bad" outcomes.
Speci c and Nonspeci c Drug E ects:
• Speci c drug e ects are based on physical and biochemical interactions with a target site in
living tissue.
• Nonspeci c drug e ects are in uenced by an individual's background, mood, expectations,
perceptions, and attitude towards the drug-administering person.
Placebo e ect
• Plaque is not a "fake" pill but a pharmacologically inert compound with therapeutic and side
e ects.
• Belief in a drug can produce physiological e ects, including measurable changes like altered
gastric acid secretion, blood vessel dilation, and hormonal changes.
• A study showed that 70% of patients found signi cant relief from a placebo, while only 25%
were helped by the "drug."
Page 1 of 17
ff fififffi ff fffi ff ff fffi fffifi flff ff fi ff
, • The e ectiveness of a sugar pill depends on the ritual of the therapeutic treatment, which can
have both neurobiological and behavioral e ects.
• There is increasing interest in understanding the mechanism responsible for the placebo
e ect to enhance the therapeutic e ectiveness of drug treatments.
• Placebo e ects may be explained by Pavlovian conditioning, where symptom improvement is
associated with speci c characteristics of a medication, a recommending clinician, or aspects
of the medical facility.
• Deception is not necessary as patients bene t even if they are told the medication is a
placebo.
Placebo E ect and Its Contributions
• The placebo e ect may be in uenced by conscious, explicit expectation of outcomes.
• Individuals who anticipate relief may show an enhanced placebo response.
• Placebo-induced neurobiological e ects within the brain are signi cant.
• Subjects who anticipate pain relief show reduced neural activity in pain-related brain regions.
• Other factors may contribute to the placebo e ect, including social learning, anticipating a
positive outcome, and genetic variants.
• Negative expectations can increase anxiety and in uence treatment outcomes.
• The nocebo e ect, where expecting treatment failure and verbal suggestions of negative
outcomes increase anxiety and neural mechanisms, can be reduced by antianxiety drug
treatment.
• Nocebos are important to study as warnings about potential side e ects can lead to greater
side-e ect occurrence.
• The placebo is essential in pharmacology to eliminate the in uence of expectation on the
experiment’s participants.
• Some researchers use an “active” placebo or leave the placebo group untreated if an
e ective agent is available.
Double-Blind Experiments in Clinical Research
• Nonspeci c factors and variable placebo responders contribute to double-blind experiments.
• No participant or observer knows treatment received.
• Precautions prevent bias in treatment results.
• Brown (1998) and Louhiala (2009) provide more on placebo use in clinical research and
therapeutics.
Pharmacokinetic factors determine drug action
Drug Action Factors
• Chemical structure of a drug determines action.
• Dosage and bioavailability are key contributors.
• Dynamic factors contribute to bioavailability.
• These factors form the pharmacokinetic component of drug action.
Page 2 of 17
ff ffff fffiff ffff fi fl ffff ff fi ff fl fl fi ff
, Methods of drug administration in uence the onset of drug action
- The route of administration of a drug determines how much and how quickly its e ect occurs
- Systemic routes of administration distribute drugs throughout the entire body, while enteral
methods use the gastrointestinal tract
- Oral administration is the most commonly used route for drugs as it is safe, self-administered,
and economical
- Drugs must dissolve in stomach uids and pass through the stomach or intestine wall to
reach blood capillaries to be e ective
- Absorption is the movement of the drug from the site of administration to the blood
circulation
- Factors such as food in the stomach, physical activity, and rst-pass metabolism can
in uence the rate of absorption
- Some therapeutic drugs taken orally may undergo extensive metabolism, reducing their
bioavailability
- Drug plasma levels are more irregular and unpredictable and rise more slowly than those
produced by other methods of
administration due to these factors.
Page 3 of 17
fl ff fl fl fi ff
