CNS Stimulants Flashcards
Identify the main categories of harm, arising from certain drugs.
PHYSICAL HARM DEPENDENCE -Intensity of pleasure -Physical and Psychological dependence SOCIAL HARMS (e.g. violence associated with addiction/drug trade, socio-economic cost of cocaine trade (and of unemployed addicts)
Explain how route of administration can influence risk of physical harm, and dependence.
Anaphylaxis (severe hypersensitivity reaction) can result from IV drugs.
Route determines rate of onset of drug (major factor is dependence potential of the drug). Oral drugs build up over period of time then decays progressively (less dependence than IV drugs which have quicker onset of action).
Distinguish between primary and secondary risk of physical harm which may arise from drugs.
Primary risk, directly due to drug (e.g. anaphylaxis) in hospital
Secondary risk, associated with spread of infection when outside of controlled hospital environment and IV injection of drug. Secondary risk may also be linked to violence which may arise as a result of consumption of certain drugs.
Give an acute, and chronic physical harm risk of smoking.
Acute- hypoT state and fall (first time smokers
Chronic- lung cancer
Identify factors which influence craving and withdrawal.
Duration, rate of onset, drop off, and nature of “rush” felt all influence craving and withdrawal symptoms.
Drugs with short duration of action, quick onset of action, and euphoric highs have a great risk of dependence (e.g. certain IV drugs).
How does the UK Misuse of Drugs Act classify different drugs ?
UK Misuse of Drugs Act classifies controlled drugs into three classes, depending on how dangerous they are (and therefore how severe the punishment associated with each is).
ALL ILLEGAL
Class A
– Deemed “most dangerous”
– Carry the harshest punishments
Class B
Class C
– Deemed to have “least capacity for harm”
– Act demands more lenient punishment
Identify the main classes of CNS Stimulants.
Convulsants and respiratory stimulants
Psychotomimetic drugs
Psychomotor stimulants
Identify examples of convulsants and respiratory stimulants. Which of these is used clinically ?
– Doxapram (used clinically), strychnine (NOT used clinically)
Identify examples of Psychotomimetic drugs.
– Hallucinogens (LSD, psilocybin, mescaline, MDMA) – Dissociative anaesthetics (ketamine, PCP)
– Cannabis
Identify examples of Psychomotor stimulants.
– Amphetamines, khat, cocaine, nicotine
– Methylxanthines (caffeine, theophylline)
What is the general action of Psychomimetic drugs ?
Induce psychosis like states.
What is the general action of Psychomotor drugs ?
Influence how body movements are controlled and regulated by CNS. Tend to cause agitated state, hyperexcitability, and movements
DOXOPRAM
- Length of action
- Clinical uses
DOXOPRAM -Length of action: Short-acting -Clinical uses: Respiratory stimulant used in respiratory failure, including: Post-op respiratory depression Acute respiratory failure Neonatal apnoea
Describe mechanism of action of Doxopram.
Act on chemoreceptor in carotid bodies which sense oxygen saturation, through modulation of Potassium (i.e. change excitability of chemoreceptor). By doing so, altering how carotid body senses oxygen saturation and signals need to increase oxygen content of blood, thereby increasing respiratory drive via medulla.
STRYCHNINE
- Clinical uses
- Mechanism of action
STRYCHNINE
- Clinical uses: powerful convulsant (but NOT used in clinical practice) resulting in violent extensor spasms triggered by minor sensory stimuli + small doses cause improvement in visual and auditory acuity (used for that historically)
- Mechanism of action: Blocks glycine receptors (major inhibitory NT in spinal cord and brainstem, normally inhibits signals to peripheral muscles so when blocked, hypersensitising body to any stimulatory effect of NS to muscles)
Where is Strychnine derived from ?
Nux-Vomica plant
Describe the pattern of signs obtained in Strychnine poisoning.
Arched back, fixed grin, full body rigidity, respiratory depression (due to muscles not relaxing to allow breathing to occur), death
Identify the main hallucinogens. What defines a hallucinogen ?
Hallucinogens = drugs that act on 5-HT receptors and transporters.
– LSD (D-lysergic acid diethylamine)
– Psilocybin (magic mushrooms)
– Mescaline (from cacti)
– MDMA (Ecstasy)
Describe the mechanism of action of hallucinogens.
Act on 5-HT receptors and transporters (increase amount of serotonin released). They stimulate pathways via Locus ceoerulus (involved in sensory signals) and Raphe Nuclei (involved in sleep, wakefullness, mood).
E.g. MDMA increases release of serotonin from serotoninergic nerve by triggering release from vesicles within neurons, and then triggering specific transporters to work in reverse, and push excess serotonin in cytoplasm out into synaptic cleft.
Overall= elevation of sertonin on target cells in chronic way.
BUT they also interact with pathways other than the 5-HT pathway (dirty drugs). Can also interact with alpha receptors, adrenoreceptors, dopamine receptors, histamine receptors, NET transporters.
Describe serotonin pathways in the brain.
The distribution of 5-HT-containing neurons resembles that of noradrenergic neurons. The cell bodies are grouped in the pons and upper medulla, close to the midline (raphe), and are often referred to as raphe nuclei. The rostrally situated nuclei project, via the medial forebrain bundle, to many parts of the cortex, hippocampus, basal ganglia, limbic system and hypothalamus. The caudally situated cells project to the cerebellum, medulla and spinal cord.
Identify the main pharmacological effects of hallucinogens.
• Main effects are on mental processes:
– alter perception of sights and sounds
– hallucinations (visual, auditory, tactile or olfactory)
– sounds can be perceived as visions
– thought processes illogical and disconnected
– sense of wakefulness/alertness
• Other effects include
– Bad trips
(hallucinations may take on menacing quality)
(may be accompanied by paranoid delusions)
–Flashbacks (particularly visual, auditory disturbances, disruptions in normal sight)
• In excess, psychosis-like state
What is the timelines of the flashbacks which are sometimes reported as an effect of hallucinogens.
Can be reported weeks or months later, but usually days
Describe tolerance, withdrawal and dependance and risks in hallucinogen use.
Hallucinogens:
1) Tolerance
- Develops quickly (plus cross-talk between drugs e.g. mescaline use will diminish response to LSD, so take more for same effect)
2) Withdrawal and dependance
- No physical withdrawal
- Psychological effects (flashbacks, psychosis)
3) Risks
- Risk of injury and accidental death while intoxicated
- Poisoning due to mistaken identity
- Adrenergic effects with LSD
- GI effects with psilocybin
Describe the main clinical uses of the main dissociative anaesthetics.
PHENCYCLIDINE (PCP, ‘Angel Dust’)
– synthesised as a possible i.v. general anaesthetic
– found to produce disorientation and hallucinations
KETAMINE
– used for induction and maintenance of anaesthesia (esp in veterinary setting, i.e. horse tranquiliser)
Describe the main pharmacological effects of dissociative anaesthetics.
Effects resemble those of other psychotomimetic drugs:
– also an analgesic
– causes stereotyped motor behaviour like amphetamine
– hallucinations
– can give a ‘bad trip’ as LSD
Also:
– at a high dose, anesthetic properties (including suppression of respiratory function)
Describe mechanism of action dissociative anaesthetics.
Both are NMDA receptor antagonists (Ketamine also has serotoninergic actions)
Describe tolerance, withdrawal, dependance and risks in dissociative anaesthetic use.
DISSOCIATIVE ANAESTHETIC
1) Tolerance
– Rapid over regular, repeated doses
2) Dependence and withdrawal
- Both physical and psychological dependence
- Withdrawal syndromes with PCP
3) Risks
– Accidents/loss of control/automatic behaviour
– PCP: hyperthermia, convulsions
– Ketamine: overdose with heart attack/respiratory failure (rare), but at low dose may lead to dysrhythmias or heart attack due to increased SNS activity and increased HR
Identify the main groups of cannabis, and the main derivatives of cannabis with pychotomimetic properties.
Cannabis sativa and indica
Tetrahydrocannabinol (THC) and 11-hydroxy-THC have psychotomimetic properties (but milder than e.g. LSD)
Where does cannabis act in the body ?
Act on cannabinoid receptors in body (because we have endogenous cannabinoids)
Identify the main kinds of Amphetamines.
- Amphetamine (speed)
- Dextroamphetamine
- Methylamphetamine (cystal meth)
- Methylphenidate (Ritaline)
- MDMA
How similar are the chemical and pharmacological properties of different Amphetamines ?
Amphetamine, dextroamphetamine and methylamphetamine
– Very similar chemical and pharmacological properties
Methylphenidate, MDMA
– Chemically related, but considered seperately
Identify the main pharmacological effects of Amphetamine, dextroamphetamine and methylamphetamine.
• Main effects are:
– Locomotor stimulation (muscle twitchiness)
– Euphoria and excitement (short lived)
– Insomnia (decreased wakefulness)
– Anorexia (diminishes with continued use)
– Stereotypic behavior (chronic use)
• Behavioural effects
– Subjects become confident, hyperactive and talkative
– Sex drive is said to be enhanced
– Fatigue (both physical and mental) is reduced (hence may used as attention and focus drugs)
– Does not enhance mental performance, just ability to concentrate for longer
Identify any clinical uses of Methylphenidate.
AKA Ritaline, used for ADHD
Describe the mechanism of action of Amphetamines.
- Competitive inhibitors of monoamine uptake
- Displace monoamines (i.e. noradrenaline, dopamine) from vesicles into cytoplasm
- Inhibit MAO at high concentrations (which normally converts NA and dopamine into metabolites)
- Cause NET to work in “reverse” (which normally “take up synaptically released norepinephrine”), so NA released into synaptic cleft
- Also stimulates release of Dopamine into synaptic cleft
- Behavioural effects probably due to the release of dopamine rather than noradrenaline
Identify the main dopamine pathways in the brain.
Nigrostriatal
• (motor control)
i.e. twitchiness, energised effect
Mesolimbic and Mesocortical
• (behavioural effects)
i.e. elevation of mood
Tuberohypophyseal system
• (endocrine control)
Identify the main NA pathways in the brain.
The cell bodies of noradrenergic neurons occur in small clusters in the pons and medulla , and they send extensively branching axons to many other parts of the brain and spinal cord. The most prominent cluster is the locus coeruleus (LC), located in the pons. LC responsible for wakefulness and alertness. Dependance on NA signaling in this region is responsible for elevated energy levels associated with Amphetamines.
Hypothalamus and medulla also involved in NA pathways. They are specifically concerned with BP regulation (hence some SEs of Amphetamines are increased HR, increased BP and associated with CV risk)
Describe tolerance, withdrawal and dependance in Amphetamine use.
AMPHETAMINES
1) Tolerance
- Rapid tolerance to euphoric and anorexic effects, slowly for other effects.
2) Dependance and withdrawal
- Moderate dependence potential due to euphoria it produces (dependent on route of administration; IV route = rapid onset and peak elevation in euphoria which tend to increase dependance)
When would amphetamine psychosis occur ? What are its main clinical features ? What happens following this, upon cessation of amphetamines?
Amphetamine psychosis
– If taken repeatedly over a few days
– Almost indistinguishable from an acute schizophrenic attack
– Stereotypic behaviour
– After cessation, usually a period of deep sleep
• After which subject may feel lethargic, depressed, anxious and often very hungry
What plant is Khat derived from ? What is the active component of Khat ? What are its main effects ?
Catha Edulis
Contains cathinone, an amphetamine-like stimulant
Mild hyperactivity and suppresses appetite (used as a social lubricant)
What plant is nicotine derived from ?
Nicotiana Tavacum
What plant is cocaine derived from ?
Leaves of the South American shrub, Erythroxylum Coca
Describe the mechanism of action of Cocaine.
Potent inhibitor of catecholamine uptake into nerve terminals (so NA and dopamine normally taken back by NET, now NOT and elevate effects of those two systems)
– (especially dopamine)
Describe the main pharmacological effects of cocaine.
Effects resemble that of amphetamine:
– Euphoria (related to ↓ dopamine and 5-HT reuptake)
– Alertness and wakefulness
– Increased confidence and strength
– Heighted sexual feelings (but not necessarily heightened performance, which may decrease at high doses)
– Indifference to concerns/cares
Identify the main routes of administration of cocaine.
Readily absorbed by many routes
– Nasal administration damages the nasal mucosa and septum
– Free-base form (‘crack’) can be smoked
Describe tolerance, and withdrawal and dependance in Cocaine use.
COCAINE
1) Tolerance
- Occurs rapidly
2) Dependance and withdrawal
-Physical dependence mild. Strong psychological
dependence occurs
Describe risks of Cocaine use.
COCAINE
3) Risks
a) Acute: – Cardiovascular (↑BP, tachycardia, ventricular fibrillation, heart attack, respiratory arrest, stroke) (associated with elevation in NA sympathetic mediated pathways) – Muscle spasms, tremor – Hyperthermia (esp. due to ^) – Seizures, headaches, excited delirium
b) Chronic:
– Heart attacks due to furring of coronary arteries
– Malnutrition and weight loss
– Decreased libido and impotence
– Personality/mood (with dopaminergic influences)
• (e.g. anxiety, depression, repetitive behaviours, delusions, psychosis)
– “Toxic syndrome”
• similar to acute paranoid schizophrenia
Describe risks of Amphetamine use.
AMPHETAMINES
-Amphetamine psychosis – Vascular accidents (because of effects on NA pathways) (e.g. tachycardias, arrhythmias, ↑BP) – Cerebral convulsions & coma – Excitation syndrome (hyperthermia/tachycardia) – Anorexia – Cognitive impairment – Personality/mood – Chronic paranoid psychosis
Where are methylxanthines found ? How strong are their effects on the CNS ?
Various beverages (e.g. tea, coffee, cocoa) contain methylxanthines which have mild CNS stimulant effects
Identify the main methylxanthines.
Caffeine and Theophylline
Identify the main pharmacological effects of caffeine and theophylline.
– CNS stimulants
– Diuretics
– Cardiac muscle stimulants
– Smooth muscle relaxants (especially bronchial)
– Psychological effects: reduce fatigue and improve mental performance without any euphoria
Describe mechanism of action of Methylxanthines.
– Inhibit cAMP/cGMP phosphodiesterases
– Block purine receptors (mechanism through which caffeine influences HR etc.)
• adenosine receptors of the A1 and A2 subtype
– Diuresis possibly due to vasodilation of the afferent glomerular arterioles causing ↑ GFR
Identify any clinical uses of caffeine and theophylline.
Few clinical uses for caffeine but theophylline can be
used as a bronchodilator in severe asthma attacks (esp when salbutamol or other drugs are not effective or contraindicated)
To what extent does dependance occur with Methylxanthines ?
Tolerance and habituation develop to a small extent
Identify drugs in class A, B, and C.
• Class A – Cocaine, mephamphetamine, LSD, ecstasy • Class B – Amphetamine, ketamine, cannabis, mephylphenidate • Class C – Khat
