Pharmacology Flashcards
What is pharmacokinetics?
What the body does to a drug
What are the four actions of drugs in the body?
- Absorption
- Distribution
- Metabolism
- Excretion
What are mechanisms of absorption? (4)
- Active transport
- Diffusion
- Facilitated diffusion
- Endocytosis
What are the variables of absorption? (4)
- pH
- Vascularity (e.g. shock reduces SC absorption)
- Surface area
- Contact time (e.g. with food = slower gastric emptying)
What is the definition of bioavailability?
Rate and extent to which an administered drug reaches the systemic circulation (e.g. IV = 100%)
What is first pass effect?
A phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation. First have to pass
- Intestinal lumen
- Intestinal wall
- Liver
- Lungs
Where are microsomal enzymes located? Give an example.
SER e.g. cytochrome p450
What is the role of microsomal enzymes in a) phase 1 rxns and b) phase 2 rxns?
Phase I reactions – biotransform substances
Phase II – glucuronidation
Where are non- microsomal enzymes located? Give an example.
Cytoplasm and mitochondria e.g. conjugases/esterases/alcohol dehydrogenase
What is the purpose of phase 1 metabolism?
polarise lipophilic drugs, reduction / oxidation / hydrolysis
catalysed by cytochrome P450 system
What is the purpose of phase 2 metabolism?
conjugation, e.g. glucuronic acid, polarisation of drugs to be excreted by renal or biliary systems
What is first order metabolism?
catalysed by enzymes, rate of metabolism directly proportional to drug concentration
What is zero order metabolism?
enzymes saturated by high drug doses, rate of metabolism is constant, e.g. ethanol, phenytoin
What is pharmacodynamics?
- What the drug does to the body
- Its effect on cellular receptors via signal transduction
Are microsomal enzymes seen more in phase 1 or phase 2 reactions?
Phase 1.
Non- microsomal = phase 2
Which cranial nerves are parasympathetic?
CN 3, 7 , 9 , 10
What neurotransmitter do
a) parasympathetic
b) sympathetic
post- SYNAPTIC nerves release?
BOTH release acetylcholine
What kind of receptor does acetylcholine act on?
NICOTINIC receptor
What neurotransmitter do
a) parasympathetic
b) sympathetic
post-GANGLIONIC nerves release and what do they act on?
a) acetylcholine -> muscarinic receptor
b) noradrenaline -> alpha/beta adrenoreceptors
What is the principal neurotransmitter in the body?
Acetylcholine
What receptor does Ach interact with in the somatic nervous system?
Post-synaptic nicotinic receptors at the neuromuscular junction.
Give examples of adverse muscarinic agonist effects.
- Diarrhoea.
- Urination.
- Miosis.
- Brachycardia.
- Emesis (vomiting).
- Lacrimation.
- Salivation.
Give 2 examples of Ach action in the CNS.
- Motion sickness; Ach stimulates the vomiting centre in the brain.
- Ach leads to increase dopamine re-uptake and so can worsen the symptoms of Parkinson’s.
Briefly describe catecholamine synthesis.
Tyrosine -> L-DOPA -> Dopamine -> Noradrenaline -> Adrenaline.