Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, pharmacology module.
Phar 4 on psychoactive drugs, stimulants (cocaine, nicotine): stimulate or increase the activity of nerves within the central nervous system
- LO1: Administration: Predict how the route of admi...
PD/PK theory: stimulant drugs
- stimulants: drugs that stimulate/ increase activity of nerves within central nervous system
=> ex: cocaine & nicotine
Pharmacokinetics: Cocaine & Nicotine
- plant-based (cocaine: erythroxylum coca plant - nicotine: nicotiana tabacum)
- induce an euphoric “high” in the brain
- routes of administration:
r
1) inhalational (smoking/ inhaling): max effets in 1.5 min in the brain
=> lungs (alveoli) - heart (LA) - systemic circulation
2) intravenous (injecting): max effets in 3 min in the brain
=> venous system - heart (RA) - lungs - heart (LA) - sys.
3) intranasal (snorting): max effets in 15 min in the brain
⑧ Hepatic portal
E
liver Small intestine
=> nasal sinus - diffuse into capillary system - venous system - heart - lungs - heart - sys.
4) oral (eating/ drinking): max effets in 60 min in the brain
=> gastrointestinal tract (stomach + small intestine) - hepatic portal venous system - liver - ...
- “crack” cocaine (mix of cocaine hydrochloride & alkaline solutions) => not degraded when heated
=> inhale cocaine
- cocaine metabolism: cholinesterase enzymes (or plasma cholinesterases) in liver
=> half-life = 20–90 min
deactivate the drugs
- nicotine metabolism: cytochrome P450 enzymes in liver
(metabolites are inactive)
=> half-life = 1-3h
- inhalation route + rapid metabolisation & clearance => addictive potential of the drugs
(re-administer the drug to maintain effects) => “crack” = most addictive (drug seeking behaviour)
Pharmacodynamics: targets
- nicotine: selective for nicotinic acetylcholine receptor
- cocaine: less selective for catecholamine reuptake proteins + sodium channels (only at high dose)
selectivity: linked to dose
, ex of catecholamines
- similarities (lipophilic ring structure - intermediate linking bond - amine group)
=> cocaine blocks dopamine reuptake proteins by using them BUT slowly (substrate)
=> dopamine can’t access => remain in synapse longer => larger response (0 affinity change)
(longer + more intense)
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