3. CNS stimulants Flashcards by Alix Wrighton

Three main categories of harm for CNS stimulants?

1. Physical harm
– Acute vs chronic risks (e.g. nicotine)
– Route of administration
• (both primary and secondary risk)
• Associated risks like needles and sharps injury, BBV transmission

Dependence
– Intensity of pleasure (“rush”, “high”)
• Tolerance, craving, withdrawal
– Two types: Physical vs psychological dependence
Social harms

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Name 2 Convulsants and Respiratory Stimulants

Doxapram

Strychnine

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Doxapram, drug features?

Use?

Convulsants and Respiratory Stimulants
– short-acting respiratory stimulant used in respiratory failure, e.g.
• post-operative respiratory depression
• acute respiratory failure • neonatal apnoea

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Strychnine:
Class?
Use?
Effect?
MoA?

Class: Convulsants and Respiratory Stimulants

Use:
Poison, convulsant
Small doses cause an improvement in visual and auditory acuity

Effect: violentextensorspasms triggered by minor sensory stimuli

MoA: blocks glycine receptors

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Different classes of psychotomimetic drugs?

Hallucinogen

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What is the action of hallucinogens?

Examples

Drugs that act on 5-HT receptors and transporters:
– LSD (D-lysergic acid diethylamine)
– Psilocybin (e.g. magic mushrooms)
– Mescaline (e.g. from cacti)
– MDMA (Ecstasy)

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Where are the serotonin pathways in the brain?

Locus coeruleus
• (sensory signals)

Raphe nuclei
• (sleep, wakefulness and mood)

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What is the raphe nuclei?

The raphe nuclei are a moderate-size cluster of nuclei found in the brain stem. Their main function is to release serotonin to the rest of the brain. Selective serotonin reuptake inhibitor (SSRI) antidepressants are believed to act in these nuclei, as well as at their targets.

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What is the 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

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Negative pharmacological effects of hallucinogens?

‘Bad trip‘
– hallucinations can take on a menacing quality – may be accompanied by paranoid delusions
‘Flashbacks’
– can be reported weeks or months later

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What is the tolerance issues of hallucinogens?

– develops quickly (plus cross-talk between drugs)

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Dependence of hallucinogens?

There is no physical withdrawal syndrome

HOWEVER, Psychological effects (e.g. “flashbacks”, psychosis)

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Name 4 associated risks when taking hallucinogens?

Risk of injury and accidental death whilst intoxicated
Poisoning due to mistaken identity
Adrenergic effects with LSD (e.g. increase in symp so… increase in CVS parameters)
GI effects with psilocybin

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Name 2 dissociative anaesthetics?

Phencyclidine (PCP, Angel dust)

Ketamine

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What is Phencyclidine (PCP, ‘Angel Dust’)?

Use

Dissociative anaesthetics
– synthesised as a possible i.v. general anaesthetic
– found to produce SIDE EFFECTS snd on recovering experienced disorientation and hallucinations

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What is ketamine?

use

Dissociative anaesthetics

– used for induction and maintenance of anaesthesia

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How do dissociative anaesthetics and psychotomimetic drugs effects resemble?

– also an analgesic
– causes stereotyped motor behaviour like amphetamine
– can give a ‘bad trip’ as LSD
* Both are NMDA receptor antagonists**

Dissociative anaesthetics: Tolerance, Dependence, Risks?

Tolerance
– Rapid over regular, repeated doses

Dependence (physical & psychological) and withdrawal
syndromes with PCP

Risks
– Accidents/loss of control/automatic behaviour
– PCP: hyperthermia, convulsions
– Ketamine: overdose with heart attack/respiratory failure (rare)

Components of cannabis?

Tetrahydrocannabinol (THC) and 11-hydroxy-THC

“Cannabis sativa, indica”

Name 2 groups of Psychomotor Stimulants?

Amphetamine, dextroamphetamine and methylamphetamine
“Speed”

and

Methylphenidate, 3,4-methylenedioxymethamphetamine (MDMA)

Main effects of amphetamine/speed?

Main effects are:
– Locomotor stimulation
– Euphoria and excitement
– Insomnia
– Anorexia (diminishes with continued use) 
– Stereotypic behaviour (chronic use)

Behavioural effects of Amphetamine

Behavioural effects probably due to the release of DOPAMINE rather than noradrenaline.

Result:

Subjects become confident, hyperactive and talkative
Hypersexuality?
Fatigue reduction (both physical and mental)
Ability to concentrate increases

MoA of amphetamines?

Competitive inhibitors of monoamine uptake
Displace monoamines (i.e. noradrenaline, dopamine) from vesicles into cytoplasm via VMAT membrane transporter at vesicle. Causes DOP/NA into the synaptic cleft.
Cause NET to work in “reverse”

Note:
4. Inhibit MAO at high concentrations

Name the 3 pathways in which dopamine is involved?

Nigrostriatal: For motor control

Mesolimbic and mesocortical: For behavioural effects

Tuberohypophyseal system: Endocrine contrl

What are the two NA pathways in the brain?

Locus coeruleus: For wakefullness and alterness Medulla/hypothalamus: For bp regulation

Amphetamines: Tolerance, Dependence

Rapid tolerance to euphoric and anorexic effects, slowly for other effects. Moderate dependence potential due euphoria it produces. “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 & often very hungry

Amphetamines, 7 risks?

– Vascular accidents (e.g. tachycardias, arrhythmias, ↑BP) – Cerebral convulsions & coma – Excitation syndrome (hyperthermia/tachycardia) – Anorexia – Chronic paranoid psychosis – Cognitive impairment – Personality/mood

What is Khat?

Psychomotor stimulant (Catha edulis) Contains cathinone, an amphetamine-like stimulant More mild but still class E drug in UK

Nicotine class?

Psychomotor stimulants

MoA of cocaine?

Potent inhibitor of catecholamine uptake into nerve terminals – (especially dopamine) Prevent reuptake >> triggering release

Effects of cocaine?

``` Similar to amphetamine... – Euphoria (related to ↓ dopamine and 5-HT reuptake) – Alertness and wakefulness – Increased confidence and strength – Heighted sexual feelings – Indifference to concerns/ cares ```

Administration of cocaine?

– Nasal administration damages the nasal mucosa and septum | – Free-baseform (‘crack’ )can be smoked

Cocaine: Tolerance, Dependence, Risks

Tolerance to occurs rapidly. Physical dependence mild. Strong psychological dependence occurs.

Risks of cocaine, acute?

``` Risks (acute) – Cardiovascular (↑BP, tachycardia, ventricular fibrillation, heart attack, respiratory arrest, stroke) – Muscle spasms, tremor – Hyperthermia – Seizures, headaches, excited delirium ```

Risks of cocaine, chronic?

Risks (chronic) – Heart attacks due to furring of coronary arteries – Malnutrition & weight loss – Decreased libido and impotence – Personality/mood • (e.g. anxiety, depression, repetitive behaviours, delusions, psychosis) – “Toxic syndrome” • similar to acute paranoid schizophrenia

Where are methyxanthines found?

Various beverages (e.g. tea, coffee, cocoa)

Main two methylxanthines?

Caffeine | Theophylline

Effects of methyxanthines?

CNS stimulants Diuretics Cardiac muscle stimulants Smooth muscle relaxants (bronchial **) Main psychological effects are to reduce fatigue & improve mental performance without any euphoria

MoA of methylxanthines?

Mechanism of action: 1. Inhibit cAMP/cGMP phosphodiesterases 2. Block purine receptors • adenosine receptors of the A1 and A2 subtype 3. Diuresis possibly due to vasodilation of the afferent glomerular arterioles causing ↑ GFR

Tolerance and habituation in methylxanthines ?

Develop to small extent

Few clinical uses for caffeine but theophylline can be used as a ____________ in severe asthma attacks

Few clinical uses for caffeine but theophylline can be used as a bronchodilator in severe asthma attacks