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
