4 - Legal Drugs of Abuse Flashcards
Name the conditions required for substance use to be determined as abuse
One of these must be met:
- Continued use despite social/interpersonal issues
- Repeated use causing failure in responsibilities
- Repeated use causing physically hazardous situations
- Use resulting in legal problems
Name three legal substances that are abused and their effect
Caffeine, nicotine, alcohol
All increase dopamine in the brain
What type of drug is caffeine?
Stimulant
Name the physiological effects of caffeine
- Stimulates CNS
- Relaxes smooth muscle
- Can be a diuretic (increase urine production)
As a drug, what is the benefit of caffeine being water-soluble?
Readily crosses blood-brain barrier
When is caffeine used?
Recreationally and medicinally to reduce fatigue/increase alertness, energy and productivity
How does caffeine work?
- Agonist at adenosine receptors (A1 & A2A), blocks adenosine from binding
- Adenosine prompts GABA release which blocks impulses between nerve cells in brain - caffeine inhibits this
- Increases epinephrine (adrenaline) levels -> increased endurance
What are the physical effects of caffeine?
- Increased alertness
- Increased metabolic rate
- Increased anxiety
- Increase BP
- Diuretic
- Decreased risk of CV disease & diabetes
What is the LD50 and t1/2 of caffeine?
LD50 = 150-200mg/kg
t1/2 = 3-4 hours
What are the active metabolites of caffeine, their effects and their t1/2?
Paraxanthine - t1/2 = 4-6 hrs Increased alertness
Theobromine - t1/2 = 5-6 hrs Lowered BP
Theophylline - t1/2 = 5-8 hrs Bronchodilator (asthma)
What is the long lasting synaptic effect of caffeine use?
Increased adenosine sensitivity
Increased adenosine receptor density
- Feel more tired when not taking caffeine - physical dependence
What are the withdrawal symptoms of caffeine?
Depression
Fatigue
Irritability
Headaches
What type of drug is nicotine?
Stimulant, but it relaxes a person due to increased dopamine
Why does nicotine readily cross the blood-brain barrier?
It’s a lipophilic free base
Where is nicotine absorbed?
Intestines only because it is basic (only absorbed in alkaline environments)
Define biphasic action
When a drug can act as both an agonist and antagonist (inc. decr. acetylcholine transmission)
Nicotine has biphasic action. Explain
Agonist - low doses, mimics NT
Antagonist - high doses, blocks NT
What effects does nicotine have on the nervous systems?
CNS & PaNS (parasympathetic) - increased HR, BP, respiration
CNS - increased adrenaline, information processing, mental performance, memory
PeNS (peripheral) - increased HR, BP, acid production in stomach
Why is inhalation the most addictive form of nicotine administration?
cmax reached within 10s
Effects go away within few mins -> frequent smoking
Define first order elimination
Amount of drug eliminated is directly proportional to remaining concentration within the body
What is the t1/2 and LD50 of nicotine?
t1/2 - 2 hrs
LD50 - 30-60mg (difficult to occur via inhalation)
Where and how is nicotine metabolised?
Lungs
Kidneys - P450 enzymes
Liver - aldehyde oxidase
What is nicotine’s metabolites?
Nicotine iminium -> cotinine -> trans-3-hydroxy cotinine
What are the long-term health effects of nicotine use?
Increased risk of CV disease
Cancer
Chronic obstructive pulmonary disease (COPD)
Emphysema
What are the symptoms of nicotine withdrawal?
Constipation
Headache
Irritability
What is a unit of alcohol?
1 unit = 10ml
What are the effects of alcohol per the unit ranges listed?
1-2, 4-6, 8-9, 10-12, 12+
1-2 - increased HR, more social & talkative
4-6 - impaired judgement & decision making, light-headedness, decreased reaction time & co-ordination
8-9 - decreased reaction time & vision, slur, hangover
10-12 - drowsy, increased risk of accident due to decreased co-ordination
12+ - alcohol poisoning, vomiting, coma, death
Ethanol enters tissues proportional to water content, what does this mean?
High concentration in blood & brain, low concentration in muscles/fat
How much alcohol is absorbed in the small intestine?
80%
How and where is alcohol metabolised?
95% metabolised by alcohol dehydrogenase & P450 enzymes
85% - liver
15% - stomach
What is the process of alcohol metabolisation?
Ethanol + alcohol dehydrogenase -> acetaldehyde
Acetaldehyde + aldehyde dehydrogenase -> acetic acid
How does alcohol affect the brain?
Ethanol inhibits NMDA glutamate & GABA receptors
What is BAC dependent on?
- Amount of ethanol consumed
- What time consumed
- Metabolic rate
- Health & drinking habits of perrson
