Drugs of Abuse Flashcards
Which NT plays a major role in motivation and behavioral reinforcment?
Dopamine (DA)
Describe the mechanism behind addiction as a “chronic relapsing disease of maladaptive learning.”
Repeated or sustained exposure to many drugs involved in substance use disorders leads to synaptic adaptations in one or more of the above pathways; these adaptations resemble learning in many ways; at a cellular level the basic learning functions, long-term potentiation (LTP) or long term depression (LTD), are known to occur at DA and other synapses in the NAc, VTA and other reward structures. Many signaling pathways appear to be involved.
Definition - Tolerance
Tolerance occurs when a standard dose of drug, repeatedly administered, produces progressively less effect, or when an increasing dose of drug is required to produce the same intensity of effect after repeated administration.
Definition – Cross Tolerance
Tolerance to the effects of other drugs acting by the same mechanism (usually through the same type of receptors).
Definition – Physical Dependence
Occurs when sustained or repeated administration of a drug leads to a condition in which normal physiological function requires continued presence of the drug. Removal of the drug results in a temporary disturbance of function, known as the “withdrawal” or “abstinence” syndrome, that is characteristic for each drug class. Withdrawal syndromes can be suppressed by re- administration of the active drug or a related drug (e.g. methadone can suppress heroin withdrawal); cross-dependence.
Definition – Conditioned Withdrawal Syndrome
Return to an environment in which drugs have previously been used may induce intense craving and symptoms of withdrawal.
Definition – Addiction
Describes the overall pattern of drug use by an individual - characterized by an over- whelming involvement with the use of a drug, the securing of its supply, and by a high tendency to relapse after withdrawal. Addiction may be present in individuals displaying little or no tolerance and physical dependence. Such conditions are known as substance use disorders, characterized in their most intense forms by lifestyles dominated by drug seeking and drug using behavior.
List – Drug Classes
- Alcohols
- Cannabinoids
- Opiates
- Stimulants
- CNS Depressants
- Hallucinogens
List – Alcohols
- Ethanol
- Methanol
List – Cannabinoids
- Marijuana (THC)
- Synthetic Cannabinoids (“Spice”)
List – Opiates
- Morphine
- Heroin (Diacetylmorphine)
- Oxycodone (OxyContin)
- Hydrocodone (Vicodin)
- Methadone
- Meperidine
- Fentanyl
List – Stimulants
- Caffeine
- Nicotine
- Cocaine
- Amphetamines (Dexamphetamine, Methamphetamine)
- Phenylethylamine (PEA)
- Phenylpropanoamine (PPA)
- Methylene-dioxyamphetamine (MDMA, “Ecstasy”)
- Synthetic Canthinones (“Bath Salts”)
List – CNS Depressants
- Barbiturates
- Benzodiazepines
List – Hallucinogens
- LSD (Lysergic Acid Diethylamide)
- PCP (Phencyclidine)
- Mescaline, Psylocibin
- Salvinorum A (kappa opioid receptor agonist)
Cocaine (Stimulant)
Method of Administration & Effects
Euphoria –> depression –> mild dysphoria –> craving.
- Intranasal (power form, ‘cocaine’) - inc HR, inc BP
- IV, smoking (free base form, ‘crack’) - v. intense effects with v. short duration; leads to binge use
- Oral (power form, ‘cocaine’) - prolonged intense stimulation with high risk CV & CNS toxicity
Cocaine (Stimulant)
Method of Action
- blocks DAT, NET, SERT
- blocks reuptake of DA, NE, 5HT
- increased DA, NE, 5HT at the synapse
note - also used as local anesthetic (blocks Na+ channels)
How are cocaine and amphetamines similar? different?
- Same - effects; different - mechanism of action.
- Cocaine has a much shorter duration of action than amphetamines, and its actions are activity-dependent.
Cocaine (Stimulant)
Chronic Use
- Sensitization –> tolerance. Withdrawal – anhedonia/chronic depression, cravings, increased appetite, lethargy.
- Cardiac arrythmias and damage (enlarged heart).
- Paranoia and psychotic behavior (similar to that seen with amphetamines).
- Sexual dysfunction.
- Damage to the nasal septum from repeated local vasoconstriction (intranasal route).
Amphetamines (Stimulant)
List Various Types
Synthetic benzylethylamine derivatives.
Methamphetamine.
Dexamphetamine (D-isomer) is more active.
Amphetamines (Stimulant)
CNS Effects
CNS stimulation - increased altertness, concentration, delays onset of fatigue. Depression of appetite.
In drug naive users - elation and euphoria; sometimes irritability and anxiety.
Amphetamines (Stimulant)
Mechanism of Action
- Enters pre-synaptic neuron by diffusion, DAT, or NET.
- Inhibits MAO (inactivates NTs) –> increases cytoplasmic concentration of DA, NE, 5-HT.
- Excellent substrate for VMAT (transfers NTs into vesicles) –> displaces DA, NE, 5-HT –> increases cytoplasmic concentration of DA, NE, 5-HT.
- Elevated cytoplasmic concentrations of DA, NE, 5-HT invert the usual concentration gradien, plasma membrane transporter operates in reverse, releasing DA, NE, 5-HT into the synaptic cleft.
- In the CNS, stimulation of DA receptors in nucleus accumbens and caudate-putamen is critical to the
euphoriant and motor effects of amphetamines.
Amphetamines (Stimulant)
Chronic Use
Prescription medications (“speed”), IV amphetamines – severe paranoia and psychotic behavior, violent crime. Other effects – sinus arrhythmias, paroxysmal tachycardia, and heart block.
Methamphetamine (“meth”) – smoked; manufactured from pseudoephedrine-containing starting materials. “Meth heads” or “tweakers” can remain awake for days before crashing; present with psychoses, skin lesions, and dental problems (“meth mouth”).
Note - Relapse rates for recovering addicts are high, and there is good evidence for chronic brain damage in addicts.
Methylene Dioxymethamphetamine (MDMA, Ecstasy, X, Molly)
Mechanism of Action
- Substrate for SERT –> depletes brain 5HT levels.
- DA release.
Methylene Dioxymethamphetamine (MDMA, Ecstasy, X, Molly)
Effect and Toxicity
Effect – generally positive mood, mild hallucinations, altered perception of time & space, depersonalization (think of someone at a rave).
Toxicity – increased susceptibility to heat stress and dehydration, renal failure, tachycardias, seizures - deaths in adolescent users are reported (think of Drop Dead Diva episode).
What is the treatment for an acute amphetamine or cocaine overdose?
Diazepam - control of agitation and seizures/
Symptomatic control of arrythmias and HTN.
What is the treatment for addiction to amphetamines and cocaine?
Withdrawal - irritability, lethargy, hunger; chronic depression and anhedronia (inability to feel pleasure) –> high rates of relapse.
Craving may never go away; attempt behavioral treatment.
List some military and medical uses of stimulants.
- Military - delay fatigue in pilots.
- Medical - narcolepsy, ADHD.
Methylphenidate (inhibits DAT), atomoxetine (inhibits NET) used to treat ADHD; very few reports of abuse.
Marijuana (Cannabinoids, THC)
PK/PD
- Absorption rapid after smoking; slower after injestion.
- Peak plasma levels at l0-30 min.
- Rapid decay by redistribution in adipose tissue.
- Metabolism in liver. Active metabolite 11-hydroxy-THC has psychoactive potency ~ THC.
- Excreted in urine and feces for days to weeks.
• Most of the metabolism takes place in the liver. Δ9-THC and other cannabinoids are converted to many oxygenated metabolic products, some of which continue to have psychoactive potency. Active metabolite: 11-hydroxy-THC, major metabolite, potency comparable to that of THC.
Marijuana (Cannabinoids, THC)
Physiologic Effects of 1 Cigarette
- Tachycardia
- Euphoria (“High”)
- Relaxation & Sedation
- Psychomotor Impairment
- Dry Mouth, Hunger, Peripheral Vasodilation (Red Conjunctiva)
Higher doses of THC can cause very confused, disorganized thinking, hallucinations, and delusions; the euphoria can turn to anxiety, panic, and paranoia.
Marijuana (Cannabinoids, THC)
Mechanism of Action
CB1/CB2 –> inhibits adenylyl cyclase.
Marijuana (Cannabinoids, THC)
Chronic Use
- Respiratory - bronchitis, asthma, lung cancer (concentration of polycyclic HCs is higher than in tobacco smoke).
- Suppression of immune system; increased infections.
- Decreased gonadotropins (inhibition of spermatogenesis, placental function, etc.)
- Amotivational syndrome - personality change, decreased interest in the achievement of conventional goals, severe memory loss, and impairment of mental performance.
Spice (and other designer THC-like drugs) – psychosis, seizures.
List some medicinal uses of THC (dronabinol) and marijuana.
N/V during chemo, glaucoma, pain relief, improved appetite.
Hallucinogens
General Effects of this Drug Class
- perceptual disturbances from changes in visual, auditory and/or temporal perception (shapes, colors, sounds, time) to frank delusions
- sometimes, marked affective changes, making the experience either pleasurable or frightening
Hallucinogens
4 Major Drug Classes
- Lysergic Acid Diethylamide (LSD)
- Anticholinergic Hallucinogens (Atropine, Scopolamine)
- Phencyclidine (PCP)
- Kappa Opioid Receptor Agonists (Salvinorum A)
Note - high dose of amphetamines (especially MDMA) or cannabinoids may also produce some hallucinogenic actions.
LSD/Lysergic Acid Diethylamide (Hallucinogen)
Effects and Chronic Use
- somatic (1-2 hrs) - dizziness, pupil dilatation, weakness, tremor, nausea, paresthesias
- perceptual (2-6 hrs) - blurred vision, difficulty in focusing, altered awareness of shape and color, micropsia, macropsia, hallucinations
- affective symptoms - elation, euphoria or dysphoria, depression, fear, paranoia, panic (2-5 hrs); mood swings between these states; after 6 hrs, detachment
Marked tolerance can occur; no evidence of physical dependence or compulsive drug use.
LSD/Lysergic Acid Diethylamide (Hallucinogen)
Method of Action
partial agonist at 5HT-R
LSD/Lysergic Acid Diethylamide (Hallucinogen)
Related Drugs
- psilocybin and psilocin (mushrooms)
- mescaline (peyote cactus)
- dimethyltryptamine
- bufotenin
Anticholinergics – Atropine, Scopopamine (Hallucinogens)
High doses may produce a delirious state with hallucinations. Elderly patients are very sensitive. Not usually perceived as pleasurable; little abuse potential.
Hot as a hare (increased body temp), Blind as a bat (mydriasis, dilated pupils), Dry as a bone (dry mouth, dry eyes, decreased sweat), Red as a beet (flushed face), Mad as a hatter (delirium).
PCP/Phencyclidine (Hallucinogen)
also, Ketamine (Hallucinogen)
Effects - Acute, High Dose, and Chronic
Developed as anesthetic; analgesia, amnesia, poor muscle relaxation, dysphoric reactions, an violent psychotic behaviors.
Acute actions - slurred speech, staggering gait, blank stare, catatonic muscular rigidity, confusion, drowsiness, hypersalivation, sweating, lasting up to 24 hours.
High doses – stuporous, comatose state for 4-6 hours followed by bizarre, unpredictable, aggressive behavior, paranoid psychoses (long duration, sometimes returns long after drug use), convulsive episodes, hypertensive crises.
Chronic use - difficulty in thinking, memory deficits, and speech impairment; intensifies psychotic behavior in schizophrenics.
PCP/Phencyclidine (Hallucinogen)
also, Ketamine (Hallucinogen)
Method of Action
channel blockers at the NMDA receptor,
Salvinorum A (Hallucinogen)
Use and Effects
A kappa opioid receptor agonists. Used in Mexico for divination and shamanism; recent increased recreational use. 1 hour, rapid-onset hallucinatory experience.
What is the treatment for a hallucinogen drug overdose?
- Protecting patient and others from the psychotic behavior. “Talk down” – i.e. calm quiet reassurance of subject (may not be effective with PCP).
- Symptomatic:
- Diazepam for convulsions.
- Haloperidol for psychotic episodes; avoid anticholinergic phenothiazines due to anticholinergic psychotic symptoms.
- Hydralazine for PCP hypertension.
Alcohol
Metabolism
90% in liver - major and minor metabolic pathways. Rate is limited by NAD+ availability. A constant amount (not a constant fraction) is eliminated per unit time; ~ 7 gm/hr (1 shot = 14 gm).
Major – EtOH + NAD+ –> (*ADH, alcohol dehydrogenase) –> acetaldehyde.
Minor – EtOH + NADPH –> (*CYP2E1) –> acetaldehyde.
Common – Acetaldehyde + NAD+ –> aldehyde dehydrogenase –> acetate.
Alcohol
Peripheral Effects (Liver, GI, CV)
- Liver - reduced NAD+ –> fatty acid synthesis increased, fatty acid oxidation decreased; plasma free fatty acid levels increased; triglycerides accumulate in the liver (fatty liver).
- GI Tract - stimulates gastric acid secretion –> stomach irritant (gastric ulcer) and reduces intestinal absorption (diarrhea, “alcohol shits”).
- CV - vasodilation –> flushing, feeling of warmth, heat loss with potential hypothermia at low temperatures; increased sympathetic tone (compensation) –> tachycardia, arrhythmia.
- Modest amounts are cadioprotective (increased HDL, decreased stroke); large amounts cause CV myopathy and increased risk of stroke.
Alcohol
Central Effects
CNS depression = “intoxication” – disinhibition, euphoria (increased DA due to disinhibition), “reward” pathways.
Note - EtOH and nicotine show addictive effects on DA release in nucleus accumbens.
Inhibition of vasopressin secretion –> diuresis, dehydration.
Alcohol
Mechanism of Action
(X) NMDA (Glu), (+) GABA
- blocks glutamate (NMDA)-activated cation current –> reduces synaptic transmission
- allosterically potentiates GABA –> increase Cl- conductance
Alcohol
BAC & Effects
- < 1 mg/ml
- 1-2 mg/ml
- 2-4 mg/ml
- 4-5 mg/ml
- < 1 mg/ml - mild euphoria, increased reaction time, impaired judgment, increased risk of accident
- 1-2 mg/ml - irregular gait, ataxia, confusion, slurred speech, elation/euphoria with impaired cognition, sedation
- 2-4 mg/ml - emesis, stupor/severe sedation, anesthesia, respiratory depression
- 4-5 mg/ml - coma, death by respiratory depression
Methanol and Higher Alcohols
Consumed (1) accidenally, (2) in replacement EtOH, (3) contaminant in moonshine. Effects similar to ethanol.
Extremely toxic! Causes metabolic acidosis, blindness, and death in large quantities because toxic products are formed.
methanol –> (*ADH) –> formaldehyde
Ethylene Glycol (Antifreeze)
Potent CNS depressant; oxidation product glycoaldehyde is toxic to kidneys –> renal failure, death from uremia.
Discuss one working definition of alcoholism.
- Continued consumption of alcohol is necessary to prevent the onset of withdrawal symptoms.
- Chronic ethanol consumption produces physical and psychological dependence.
- Persons who are relatively insensitive to the intoxicating actions of alcohols are more likely than highly sensitive subjects to become alcoholics; this may be related to genetic polymorphisms in systems metabolizing alcohols or in systems modulated by alcohols.
Daily Alcohol Use
Moderate (1-2/day) v. Heavy
Moderate - significantly reduced risk of atherosclerotic heart disease and cardiac infarction (inc HDL levels); recently, reduced cognitive decline in older women (less small strokes etc?).
Heavy - increased incidence of HTN, arrhythmias, and stroke.
What are the two patterns of EtOH abuse?
- Binge Drinkers - bouts of severe intoxication for 1-4 days with abstinence between binges (i.e., week-end binges).
- Continuous Drinkers - continuous slow rate of consumption with no abstinence more than a few hours; rarely wildly intoxicated.
Both tolerance and physical dependence occur.
What are the mechanisms of EtOH tolerance?
- Metabolic - induce CYP2E1 metabolism.
- Pharmacodynamic - DA release by other rewarding agents is reduced –> increased alcohol use to maintain reward “value”.
Due to physical dependence on EtOH, what are the symptoms of withdrawal?
Withdrawal starts in 12-24 hours since last drink; recovery complete in 5-7 days. Symptoms can be lethal -
- tremors (severe), hyper-reflexia, sweating, cramps, vomiting
- visual hallucinations, delirium tremens (day 3-4)
- hyperthermia, CV collapse
- generalized tonic-clonic seizures
What are the neural effects of chronic alcoholism?
- peripheral neuropathy, paresthesias, dec DTRs, pellagra (VitB1/thiamine deficiency
- Wernicke’s encephalopathy – partial paralysis of eye movements, nystagmus, ataxia, disorientation.
- Korsakoff’s psychosis – memory loss, confusion, confabulation.
- Cerebellar degeneration: associated with ataxia and intention tremor.
What are the nutritional effects of chronic alcoholism?
Malnutrition and avitaminosis. High calorie content of alcohol causes decreased appetite; but, EtOH is devoid of impt proteins, lipids, and vitamins.
What are other GI & sexual function effects of chronic alcoholism?
- GI - gastritis, ulcer, pancreatitis (due to exocrine pancreas hypersecretion).
- Sex Func - erectile dysfunction, testicular atrophy, decreased fertility, gynecomastia.
Alcoholism and the Liver
necrosis, fibrosis = cirrhosis –> death from liver failure
- fat accumulation
- accumulation of acetaldehyde –> increased lipid peroxidation, damage to mitochondrial and cellular membranes, depletion of glutathione, depletion of vitamins and trace metals (e.g. pyridoxine, vit. A, zinc, selenium), decreased transport and secretion of proteins
- induction of CYP2E1 –> increased metabolism of many endogenous and exogenous compounds; increased toxicity of precursors of hepatotoxins (e.g. acetaminophen)
Alcohol and Drug Interactions
induction of CYP2E1 –> increased metabolism of acetaminophen, halothane (and other anesthetics), etc. Increased metabolism of acetaminophen generates hepatotoxic metabolites.
