Download Chapter 19 Drugs: Chemical Cures, Comforts, and Cautions

Chapter 14
Drugs: Chemical Cures, Comforts,
and Cautions
Drug
• Chemical substance that affects the
functioning of living things
• May treat, diagnose, and prevent
disease
• Dates to ancient times
• Over 9900 drugs available in U.S.
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Antibacterial Drugs
• Have lowered the
death rate for
infectious diseases
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Antibacterial Drugs
• Sulfa drugs: inhibit use of folic acid by bacteria
– First antibacterial drug developed
• Penicillins: inhibit growth of microorganisms
– Antibiotic
– Group of related compounds
– Inhibit enzymes used to make cell walls
– Many people allergic
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Other Antibacterial Drugs
• Cephalosporins: related to penicillin
• Tetracycline: effective against wide
variety of bacteria – broad spectrum
antibiotic
– Inhibits protein synthesis
• Fluoroquinolones
– Inhibit bacterial DNA synthesis
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Antibiotics
• Save lives of many people every year
– Large decline in death by infectious
disease
• Bacteria eventually develop resistance
to antibiotics
• Must continually search for new
compounds
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Viruses
• Unable to replicate
on their own
• Assemble to
viruses once in
host cell
• DNA virus made of
DNA and protein
coat
• RNA virus made of
RNA and protein
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Antiviral Drugs
•
•
•
•
Cannot use antibiotics
Need antiviral drugs
Three classes
Combinations of drugs more effective
than individual drugs
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Classes of Antiviral Drugs
• Nucleoside analogs: replace nucleotides
during replication
• Reverse transcriptase: Convert RNA of
virus to DNA
– Reverse transcriptase inhibiters block enzyme
• Protease inhibitor: new copies of the virus
can’t infect new cells
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Chemicals Against Cancer
• Main problem: chemicals that kill cancer
cells can damage normal cells as well
• Antimetabolite: usually a compound that
inhibits synthesis of nucleic acids
• Alkylating agents: transfer alkyl groups
to compounds of biological importance
– Some developed from original chemical
weapons
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Miscellaneous Anticancer Agents
• Some antibiotics
• Sex hormones against cancers of
reproductive system
• Alkaloids from plants
• Typically combine treatment with
chemicals (chemotherapy) with other
strategies
– Surgery or radiation
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The Pill
• Administer derivative of progesterone
– Otherwise need to take hormone using injections
• Fools body into thinking it is already pregnant
– Prevents ovulation
• Some risks: may experience hypertension,
acne, or abnormal bleeding
– Increases risk of blood clots
– Especially in smokers
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Missed Period Pills
• Diethylstilbestrol (DES)
– low dosages may help maintain pregnancy
– High dosages can induce abortion
– Sons of women who took it may be sterile
• RU-486 inhibits action of progesterone
– Prevents establishment of pregnancy
– Need to take 2nd shot with prostaglandin
– Suffer from severe morning sickness
during and shortly after treatment
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Pill for Males?
• Problem: males produce sperm
continuously
• Have to reduce production of sperm but
not libido
• Several drugs have been tested on
mice
– Human trials have not been started
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Nerve Cells
•Neurotransmitters cross synapse
•Many different functions
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Hormones
• Chemical messengers made in
endocrine glands
• Released in one part of body to send
messages to other regions
• Control growth, metabolism,
reproduction, and other bodily functions
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Prostaglandins
• Closely related to hormones
• Act on target cells but are produced
near site where used
• Effects can differ on different tissues
• Act as mediators of hormones
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Steroids
• Based on structure for cholesterol
• Occur widely in living organisms, but not
all are hormones
• Used to reduce inflammation, increase
muscle mass, and the development of
sexual characterstics
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Sex Hormones
• Androgens: male sex hormones
• Estrogen and progesterone: female sex
hormones
– Regulate sexual cycle before, during, and
after pregnancy
• Both sexes have small amounts of each
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Drugs for Heart
• Lowering blood pressure
• Normalizing heart rhythm
– Arrhythmia: abnormal heartbeat
• Treating coronary disease
– Heart getting less O2 than needed
– Typically use drugs that release NO in body
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Drugs and the Mind
• Psychotropic drugs affect the mind
• Stimulants increase alertness, speed up
general mental process, and generally elevate
moods
• Depressants reduce level of consciousness
and intensity of reactions to environment
• Hallucinogenic drugs alter the way we
perceive things
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Depression and Mania
• Involve amines
• Norepinephrine
– High levels cause manic state
– Low levels cause depression
• Serotonin involved in sleep, sensory perception,
pleasure sensations, and body temperature
• Control levels of compounds in normal range
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Anesthetics
• General anesthetic: acts on brain to produce
unconsciousness and general insensitivity to
pain
• Developed in 19th century
– Ether used but effective dose close to lethal dose
• Modern mixtures use several different
compounds to make it safer
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Local Anesthetic
• Renders a part of the body insensitive
to pain
– Blocks nerve conduction
– First developed in 19th century
• Some of the more powerful ones
developed from cocaine
– No longer used as extensively because of
problems with toxicity
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Dissociative Anesthetics
• Dissociates person’s perception from his or
her senses
• May induce hallucinations
• Phencyclidine (PCP)
– Stored in fatty tissue
– Used as animal tranquilizer
– 1 in 1000 develop severe form of schizophrenia
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Depressants
• Ethanol most widely used
– Slows both physical and mental activity
– Probably first synthetic chemical made by humans
– Potentially fatal
– Potent teratogen
• Barbiturates
– Similar effects to alcohol
– Synergistic effect with alcohol
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Narcotics
• Produce narcosis and relief of pain
– In U.S., if also addictive, legally classified as
narcotics
• Opium – source of morphine
– Potent painkiller, cough suppressant
– Side effects: constipation, addictive, euphoria, …
– First isolated in 1805
• Codeine and heroin are just chemically
modified morphine
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Synthetic Narcotics
• Attempts have been made to make pain reliever
as good as morphine but not addictive
• Best known is Demerol
– Less effective than morphine
– Still addictive
• Methadone does not produce intoxication
– Highly addictive
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Natural Opiates
• Endorphins: naturally produced
morphine-like substances
• Short peptides, rapidly digested
• Synthetic versions that are not easily
broken down have been produced
– Still addictive
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Antianxiety Agents
• Antipsychotic agents for treatment of
maniacal forms of depression
– Reduced number of patients confined to
mental hospitals
– People will relapse if they go off medication
• Antidepressants
– Original medication is dose sensitive
– Work by enhancing serotonin uptake
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Stimulants
• Amphetamines: mimic natural brain
amines
– Based on phenylethylamines
– Used for weight reduction
– Large illegal drug market
• Cocaine: first used as local anesthetic
– Powerful stimulant
– Works by preventing reabsorption of
dopamine
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Caffeine and Nicotine
• Caffeine probably most common stimulant
– Mildly addictive
– May cause chromosome damage
• Nicotine: toxic to animals
– Used as insecticide
– Transient effect as stimulant
– Toxic, especially when injected
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Psychedelics
• Change way we perceive things
• Most powerful probably lysergic acid
diethylamide (LSD)
• Exact mechanism of action unknown
• Need only very small doses: 10–100 g
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Marijuana
• Second only to alcohol in popularity as
intoxicant
• Principal active ingredient:
tetrahydrocannabinol (THC)
• Hard to quantify effects because of variable
amount of THC in different samples
– Increases heart rate, distorts sense of time, and
impairs complex motor functions
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Marijuana and the Brain
• Activates brain’s reward system
• Causes euphoric feeling by releasing
dopamine
• Legitimate medical uses
– Treat glaucoma
– Relieves nausea of cancer patients
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Drug Problems
• Legal drugs
– May be overprescribed
– Faulty prescriptions
– Costs of drugs
• Illegal drugs
– Expensive and addictive
– Not always what they claim to be
– Societal costs
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Nonsteroidal Anti-inflammatory
Drugs (NSAIDs)
• Most widely used: acetylsalicylic acid
– Trade name: aspirin
• Effective pain reliever (analgesic), antipyretic
(fever reducer), and anti-inflammatory
• Also anticoagulant
– Good for heart attack and stroke prevention
• Side effects: stomach distress and bleeding
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Other NSAIDs
•
Ibuprofen, ketoprofen, and naproxen
– Similar shape to aspirin
– Similar properties to aspirin
•
Acetaminophen not NSAID
– Has all but anti-inflammatory properties of
NSAIDs
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How NSAIDs Work
• Inhibit cycloxygenases (COX)
• COX-1 found in stomach and kidney tissue
– Gives rise to side effects
• COX-2 found in tissue where inflammation
occurs
• Older drugs affect both enzymes
– Newer drugs affect only COX-2
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Acetaminophen
• Neither anti-inflammatory nor anticoagulant
• Overuse linked to liver and kidney damage
• Affects COX-3
– May represent mechanism to decrease pain
and fever
– No role in inflammation
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Combination Pain Relievers
• Combine with caffeine or other NSAIDs
• Buffered aspirin: contains antacids to
prevent stomach problems
• Usually available in two strengths:
regular and extra strength
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Common Cold Remedies
• Antihistamines: relieve symptoms of allergies
• Cough suppressants
• Expectorants: bring up mucus from bronchial
passages
• Nasal decongestants: repeated use may lead to
rebound effect
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Placebo Effect
• Placebo: inactive substance given in the
form of medication to a patient who
thinks it is the real thing
• People given placebo report that it
works
– For some, they actually get better
• Keep positive attitude
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New Uses for Old Drugs
• Cost of developing a drug ~$800 million
• Cheaper to use existing drug
• Aspirin: original developed as painkiller
– Prevents strokes and heart attacks
– May show promise in fighting cancer and in
delaying onset of Alzheimer’s disease
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End of Chapter 19
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