Flashcards in Pharmacology basics Deck (59)
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1
Volume of distribution
Vd= (amount of drug in body)/(plasma drug concentration)
- Vd high when drug goes everywhere OR if plasma proteins low (cirrhosis, kidney disease)
2
Half-life of drug
First-order elimination (rate of elimination proportional to drug concentration in blood= constant fraction eliminated per unit time)
- Exponential elimination
Takes 4-5 half-lives to reach steady state with a drug infused at steady rate
- 97% of a drug is excreted in 4x t1/2
** To calculate clearance of drug, need to know t1/2= (0.7 x Vd)/CL or
(0.7 xVd) / (rate of elimination of drug/plasma drug concentration)
3
Clearance (CL)
CL= rate of elimination of drug/plasma drug concentration= Vd x elimination constant (Ke)
Loading dose= Cp x Vd/F
- Cp= target plasma concentration
Maintenance dose= Cp x CL/F
- F= bioavailability
4
Zero order elmination
Drug elimination constant
- Cp decreases linearly (vs first-order exponential)
Ex: Phenytoin, Ethanol, Aspirin
5
Urine pH/Drug elimination
Weak acid (phenobarbital, methotrexate, aspirin): eliminate with bicarb
Weak base (amphetamines): eliminate with ammonium chloride
6
Nicotinic receptors
Stimulated by Ach
- Ligand-gated Na+/K+ channels
Nn= autonomic ganglia
+ Adrenal medulla
Nm= Neuromuscular junction
7
Muscarinic receptors
Stimulated by Ach
- G-protein coupled receptors of parasympathetic system
+ Sympathetic sweat glands
8
Gq receptor types
H1, alpha-1, V1, M1, M3
- HAVe 1 M&M
Activate Phospholipase C--> cleave PIP2 (lipid-derived)-->
1. DAG==> PKC
2. IP3--> Ca+2 increase in cell--> smooth muscle contraction
9
Gs receptor types
Beta1, Beta2, D1, H2, V2
Activates adenylyl cyclase
--> cAMP--> PKA-->
1. increase Ca+2 concentration in heart muscle--> contractility
2. block myosin light chain kinase (prevent smooth muscle contraction)
10
Gi receptor types
M2, alpha-2, D2
- MAD 2s
Blocks adenylyl cyclase
1. Decreased Ca+2 in heart (decreased contractility)= M2
2. Increases myosin light chain kinase activity (MLCK)--> smooth muscle contraction= alpha-2
11
Vesamicol
Blocks VAchT (packaging of Ach in presynaptic terminals)
12
Hemicholinium
Blocks ChT (influx of choline)--> can't use with choline acetyl transferase to make Ach
13
Metyrosine
Blocks tyrosine hydroxylase
- Can't convert Tyrosine to DOPA
14
Reserpine
Blocks VMAT: can't packages DA, NE, epi
15
Guanethidine, bretylium
Blocks release of Noradrenergic vesicles from presynaptic terminal (NE, DA, Epi can't get out)
16
Bethanchol
Direct cholinomimetic agonist
- Activates bowel, bladder smooth muscle
- Resistant to AchE
Use:
- Post-operative ileus, neurogenic ileus, urinary retention (nonobstructive)
17
Carbachol
Direct cholinomimetic agonist (Ach)
- Identical to Ach (not AchE resistant)
Use:
- Glaucoma, pupillary contraction, relief of IOP
"Carbon copy of Ach"
18
Pilocarpine
Direct Cholinomimetic agonist
- Contracts ciliary muscle of eye
- Pupillary sphincter contraction
- Resistant to AchE
Use:
- Stimulates sweat, tears, saliva
- Open/closed angle glaucoma
"Cry onto your pillow"
19
Neostigmine
Indirect cholinomimetic (anti-AchE)
- No CNS penetration (Neo= No-CNS penetration)
Use:
- Post-op ileus
- Neurogenic ileus, urinary retention
- MG
- Reverse NM junction blockade (post-op)
20
Pyridostigmine
Indirect cholinomimetic (anti-AchE)
- no CNS penetration
Use:
- MG (long-acting)
21
Edrophonium
Indirect cholinomimetic (anti-AchE)
Use:
- MG (short-acting)- test
22
Physostigmine
Indirect cholinomimetic (anti-AchE)
- Crosses BBB (thus can reverse CNS effects of anticholinergic toxicity)
Use:
- Atropine/anticholinergic overdose
23
Donepexil
Indirect cholinomimetic (anti-AchE)
- Increases Ach
Use:
- Alzheimer's disease
24
Cholinesterase inhibitor poisoning (organophosphate poisoning)
Organophosphates (parathion) inhibit AchE
- Pupils small, decreased breathing/HR
- Lots of fluid excretion
- Muscle twitching
(Diarrhea, diaphoresis, urination, miosis, bronchospasm, bradycardia, emesis, lacrimation, salivation)
Antidote= Atropine (anticholinergic) + Pralidoxime (regenerates active AchE- otherwise muscle spasm--> paralysis)
25
Atropine, homatropine, tropicamide
Muscarinic antagonists (M3)
Use: mydriasis, cycloplegia
"Belladonna/Nightshade"
- Atropine also decreases airway secretions, acid secretion, gut motility, bladder urgency
Toxicity of Atropine:
- Hot as a hare, Dry as a bone, Red as a beet, Blind as a bat, Mad as a hatter
** Jimson weed--> Gardner's pupil (mydriasis d/t plant alkaloids)
26
Benztropine
Muscarinic antagonist (M1)
CNS depression
Use:
- Parkinson's disease dystonia, tremor
27
Scopolamine
Muscarinic antagonist (M1)
Use: motion sickness (prevents vestibular transmission)
28
Ipratropium, Tiotropium
Muscarinic antagonist (M3) (parasympathetic control of asthma vs noradrengergic)
Use: COPD, asthma
- Blocks respiratory secretions
29
Oxybutynin
Muscarinic antagonist (M3)
Use:
- Reduce urgency in mild cystitis, reduce bladder spasms
30
