31-10-23 - CNS stimulants Flashcards
Learning outcomes
- To relate the mechanism of action of CNS stimulants to their effects, side-effects and associated risks.
- To discuss the potential direct and indirect harms associated with use of CNS stimulants.
- To classify CNS stimulants according to the UK misuse of Drugs Act and recognise some of the factors that influence classification.
Lecture outline
- Lecture outline
1) Categories of harm
2) Convulsants & respiratory stimulants – Uses, risks and side effects
3) Psychotomimetic drugs – (Ab)uses, risks and side effects
4) Psychomotor stimulants – (Ab)uses, risks and side effects
What are the 3 main categories of harm?
- 3 main categories of harm:
1) Physical harm
* Acute vs chronic risks
* Route of administration (both primary and secondary risk)
2) Dependence
* Intensity of pleasure (“rush”, “high”) - tolerance, craving, withdrawal
* Physical vs psychological dependence
3) Social harms
* Social, economic, psychological and environmental injury or damage inflicted on society either intentionally or unintentionally
How does the UK Misuse of Drugs Act classify controlled drugs?
- UK Misuse of Drugs Act classifies controlled drugs in to three classes:
1) Class A
* Deemed “most dangerous”
* Carry the harshest punishments
1) Class B
2) Class C
* Deemed to have “least capacity for harm”
* Act demands more lenient punishment
What are the 3 different types of CNS stimulants?
What are examples of each?
- 3 different types of CNS stimulants:
1) Convulsants & respiratory stimulants
* Doxapram
2) Psychotomimetic drugs
* Hallucinogens (LSD, psilocybin, mescaline, MDMA)
* Dissociative anaesthetics (ketamine, PCP)
* Cannabis
3) Psychomotor stimulants
* Amphetamines, khat, cocaine, nicotine
* Methylxanthines (caffeine, theophylline)
What type of drugs are Convulsants and Respiratory Stimulants?
What is an example of Convulsants and Respiratory Stimulants?
What are 3 clinical scenarios where it may be used?
- Convulsants and Respiratory Stimulants are a diverse group of drugs that have little clinical use
- An example is doxapram, a short-acting respiratory stimulant used in respiratory failure e.g:
1) Post-operative respiratory depression
2) Acute respiratory failure
3) Neonatal apnoea
What are Psychotomimetic Drugs?
- Psychotomimetic Drugs - “relating to or denoting drugs which are capable of producing an effect on the mind similar to a psychotic state”
What receptors do hallucinogens work on?
What are 4 examples of hallucinogens?
- Hallucinogens are drugs that act on 5-HT (serotonin) receptors and transporters
- 4 examples of hallucinogens:
1) LSD (D-lysergic acid diethylamine)
2) Psilocybin (magic mushrooms)
3) Mescaline
4) MDMA (Ecstasy)
How was 5-HT (serotonin) discovered as an NT?
What 2 structures are involved in the serotonin pathways in the brain?
What is each structure involved in?
- 5-HT (serotonin) as a NT was first identified because of LSD
- 2 structures are involved in the serotonin pathways in the brain:
1) Locus coeruleus
* (sensory signals)
2) Raphe nuclei
* (sleep, wakefulness and mood)
- Both structures are closely related
What are the main Pharmacological Effects of Hallucinogens?
What are 4 effects of hallucinogens on mental processes?
What are ‘bad trips’?
When can flashbacks be reported due to hallucinogens?
- The main Pharmacological Effects of Hallucinogens are on mental processes
- 4 effects of hallucinogens on mental processes:
1) Alter perception of sights and sounds
2) Hallucinations (visual, auditory, tactile or olfactory)
3) Sounds can be perceived as visions
4) Thought processes illogical and disconnected - Bad trips are when hallucinations can take on a menacing quality, which may be accompanied by paranoid delusions
- Flashbacks from hallucinogens can be reported weeks or months later
How quickly does tolerance develop from hallucinogens?
Describe the withdrawal from hallucinogens.
What are 4 risks of hallucinogens?
- Tolerance from hallucinogens develops quickly (plus cross-talk between drugs)
- There is no physical withdrawal syndrome from hallucinogens, but there are psychological effects (“flashbacks”, psychosis)
- 4 risks of hallucinogens:
1) Risk of injury and accidental death whilst intoxicated
2) Poisoning due to mistaken identity
3) Adrenergic effects with LSD
4) GI effects with psilocybin
What are 2 examples of dissociative anaesthetics?
What are they used for?
What receptor do dissociative anaesthetics work on?
What do dissociative anaesthetic effects resemble?
What are 3 other effects of dissociative anaesthetics?
- 2 examples of dissociative anaesthetics:
1) Phencyclidine (PCP, ‘Angel Dust’)
* Synthesised as a possible i.v. general anaesthetic
* Found to produce disorientation and hallucinations
2) Ketamine
* Used for induction and maintenance of anaesthesia
- Both of these are NMDA receptor antagonists
- Effects of dissociative anaesthetics resemble those of other psychotomimetic drugs
- 3 other effects of dissociative anaesthetics:
1) Also an analgesic
2) Causes stereotyped motor behaviour like amphetamine
3) Can give a ‘bad trip’ as LSD
Describe the tolerance and dependence of dissociative anaesthetics?
What are 3 risks with dissociative anaesthetics?
- Tolerance of dissociative anaesthetics is rapid over regular, repeated doses
- There are dependence (physical & psychological) and withdrawal syndromes with PCP
- 3 risks with dissociative anaesthetics:
1) Accidents/loss of control/automatic behaviour
2) PCP: hyperthermia, convulsions
3) Ketamine: overdose with heart attack/respiratory failure (rare)
Psychotomimetics: Cannabis.
What are other names for cannabis?
What is the active ingredient of cannabis?
- Psychotomimetics: Cannabis
- Canabis is also known as (Cannabis sativa, indica)
- Tetrahydrocannabinol (THC) and 11-hydroxy-THC, with THC being the principal psychoactive constituent of cannabis
What are psychomotor stimulants?
What are 3 different psychomotor stimulants?
How are they related?
What are 5 of the main-effects of psychomotor stimulants?
What is a chemically related drug?
- Psychomotor stimulants are drugs that act on the central nervous system (CNS) to increase alertness, elevate mood, and produce a sense of well-being
- 3 different psychomotor stimulants:
1) Amphetamine
2) Dextroamphetamine
3) Methylamphetamine - Very similar chemical and pharmacological properties
- 5 of the main-effects of psychomotor stimulants:
1) Locomotor stimulation
2) Euphoria and excitement
3) Insomnia
4) Anorexia (diminishes with continued use)
5) Stereotypic behavior (chronic use) - Stereotypic behaviour has been defined as a repetitive, invariant behaviour pattern with no obvious goal or function
- Methylphenidate, 3,4-methylenedioxymethamphetamine (MDMA) is chemically related, but considered separately
What are 4 actions of amphetamines?
- 4 actions of amphetamines:
1) Competitive inhibitors of monoamine uptake
2) Inhibit MAO at high concentrations
3) Displace monoamines (i.e. noradrenaline, dopamine) from vesicles into cytoplasm
* Encourages the release of monoamines into the synaptic region
* This done through work on VMAT
* Responsible for packing NA and DA into vesicles, so this displaces NA and DA into the cytoplasm of the cell
4) Cause NET to work in “reverse”
Describe the 3 parts of the dopamine pathways in the brain?
What are they each responsible for?
- 3 parts of the dopamine pathways in the brain:
1) Nigrostriatal
* Motor control
2) Mesolimbic & Mesocortical
* Behavioural effects
3) Tuberohypophyseal system
* Endocrine control
What are the 2 parts of the noradrenaline pathway in the brain?
What is each part responsible for?
- 2 parts of the noradrenaline pathway in the brain:
1) Locus coeruleus
* Wakefulness, alterness
2) Medulla/hypothalamus
* Blood pressure regulation
What are 3 more examples of Psychomotor Stimulants other than amphetamines?
- 3 more examples of Psychomotor Stimulants other than amphetamines:
1) Khat (Catha edulis)
* Contains cathinone, an amphetamine-like stimulant
2) Nicotine (Nicotiana tabacum)
3) Cocaine
* Leaves of the South American shrub, Erythroxylum Coca
