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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

Glycopyrrolate

Muscarinic antagonist (M3)

Use:
- Parenteral: pre-op to reduce airway secretions
- Oral: stop drooling, peptic ulcer