ICS - Pharmacology Flashcards
(53 cards)
Specificity vs sensitivity
Specificity - Number of true negatives
Sensitivity - Number of true positives
Alcohol units equation
(alcohol % by volume * volume of liquid in ml)/1000
Sympathetic vs parasympathetic nervous system
Sympathetic (Nad) - fight or flight
Pupil dilates
Increased heart rate
Bronchodilation
Decreased GI motility and secretion
Detrusor relaxes
Ejaculation
Parasympathetic (Ach) - rest and digest
Pupil constricts
Decreased HR
Bronchoconstriction
Increased GI motility and secretion
Detrusor muscle in bladder contraction
Penis points (erection)
Define Pharmacokinetics
How the body affects the drug:
Absorption, Distribution, Metabolism, Excretion (ADME)
Explain drug absorption, distribution, metabolism, excretion (Pharmacokinetics)
Absorption - Route and entry into body
Distribution - Drug distributed in plasma according to properties and size, may be taken up by organs
Metabolism - Drugs metabolised in kidney (small/water soluble) or liver (hydrophobic)
Excretion in urine or faeces
First pass vs second pass metabolism
First - Metabolism before drug reaches systemic circulation (gut/liver wall metabolism, bioavailability reduced)
Second - Actual metabolism (Phase 1 - CYP450, Phase 2 - conjugation)
Define Pharmacodynamics
How the drug affects the body
Name 4 drug targets
Usually proteins
1. Receptors
2. Enzymes (COX-1 and ACE)
3. Transporters (e.g. PPI, Diuretics)
4. Ion channels (CCB, local anaesthesia)
Define summation, synergism, antagonism, and potentiation (physicochemical)
Summation - Drugs used together and effect is as you would expect (1+1=2)
Synergism - Drugs used together and effect greater than expected (1+1>2)
Anatagonism - effect less than expected (1+1=0)
Potentiation - Drug A given with Drug B, increases effect of Drug B without effecting Drug A (1+1=1+2)
Routes of administration
Oral
IM
IV
Sublingual
Inhaled
Topical
Rectal
Intrathecal (into CSF)
Define bioavailability
Amount of drug taken up as proportion of amount administered
Bioavailability of IV drugs
1, or 100%
Factors affecting drug absorption
Motility - Certain drugs e.g. codeine affect gut motility. Impaired transit=reduced absorption
Acidity - certain drugs (antacids,PPI) can affect pH so absorption of drugs
Solubility - Eating high fat food with a fat soluble drug can cause the drug to dissolve: no absorption
Factors affecting drug distribution
Protein binding causes reduced concentration of drug in plasma. This can be overcome by using another protein binding drug to make the first one more bioavailable.
Effect of amiodarone in patient taking warfarin
Amiodarone is a protein binding drug. Will mean less warfarin binds to protein so plasma concentration will be higher
Importance of metabolism in pharmacokinetics
Enzyme induction or enzyme inhibition can cause increased or decreased effect of drug.
E.g. morphine metabolised to morphine-6-glucuronide by CYP450. Drug A inhibits CYP450 leaving more morphine in blood, increasing effect.
Drug B induces CYP450, increasing metabolism of morphine, less effect.
Examples of excretion in pharmacokinetics
Furosemide causes increased but dilute urine. As a result, drug clearance, particularly of gentimicin, is decreased.
pH of urine can be altered to purposefully remove drugs from blood.
E.g. weak bases are cleared quicker if urine acidic, and weak acids are cleared faster if urine is alkali. Therefore urine pH can be changed to alter excretion.
Give the 4 types of receptors
- Ligand-gated ion channels
- G protein coupled receptors (most common - opioids act here)
- Kinase linked receptors
- Cytosoloic/nuclear receptors
Explain action of ligand-gated ion channel
Pore forming membrane proteins that allow ions to pass through shifting electrical charge distribution
Explain G protein coupled receptors
GPCRs consist of large polypeptide chains that go intracellular and extracellular.
On activation, G proteins catalyse exchange of GDP (guanosine diphosphate) to GTP (guanosine triphosphate), causing signal cascade
Explain kinase linked receptors
kinases catalyse phosphorylation.
Binding of ligand on extracellular side causes phosphorylation of tyrosines on intracelullar side, allowing it to recruit intracellular signal mediating components.
Explain Cytosolic/ nuclear receptors
Intracellular molecules that modify gene transcription upon steroid hormone ligand binding.
N domain on outside, C on inside, zinc fingers bind to DNA.
Give examples of how chemical/receptor imbalance can lead to pathology
Chemical increase: Allergy (increased histamine)
Chemical decrease: Parkinson’s (decreased dopamine)
Receptor increase: Mastocytosis (increased c-kit receptors)
Receptor decrease: Myasthenia gravis (loss of ACh receptors)
Define agonist/antagonist
Ligands that bind to a receptor and activates it
