Pharmacokinetics and Autonomic Drugs Flashcards
what is bioavailability?
- bioavailability (F) = % of administered drug reaching systemic circulation unchanged
when is bioavailability usually 100%?
F=100% for an IV dose
why is bioavailability usually less than 100% for an oral drug?
due to incomplete absorption and first pass metabolism
what is volume of distribution (Vd)?
- amount of drug in the body / [drug] in the plasma
compartment and drug types when low volume of distribution
- compartment: blood
- drug types: large/charged molecules; plasma protein bound
compartment and drug types when medium volume of distribution
- compartment: ECF
- drug type: small hydrophilic molecules
compartment and drug types when high volume of distribution
- compartment: all tissues including fat
- drug type: small lipophilic mcs, especially if bound to tissue protein
what is the equation for half life for a first order elimination?
t1/2=0.693 x Vd / CL
what is clearance (CL)?
- volume of plasma cleared of drug per unit time
- may be impaired with defects in cardiac, hepatic, or renal function
- CL=(rate of elimination of drug / plasma drug concentration) = Vd x Ke
- Ke= elimination constant
what is loading dose?
loading dose = Cp x Vd / F
Cp = target plasma concentration at steady state
what is maintenance dose?
maintenance dose = Cp x CL x t / F
Cp = target plasma concentration at steady state
t = dosage interval (time b/w doses), if not administered continuously
maintenance dose and loading dose in renal or liver disease
- maintenance dose decreases
- loading dose is usually unchanged
what does the time to steady state depend on?
- half life
- independent of dose and dosing frequency
what is the difference between zero order elimination and first order elimination?
- zero order–rate of elimination is constant regardless of Cp
- constant amount of drug eliminated per unit time
- Cp dec linearly with time
- first order–rate of elimination is directly proportional to drug concentration
- constant fraction of drug elminated per unit time
- Cp dec exponentially with time
- applies to most drugs
which drugs are zero order?
-
PEA–a pea is round shaped like the “0” in zero order
- Phenytoin
- Ethanol
- Aspirin
what are weak acid drugs?
where do they get trapped?
how do you treat overdose?
- phenobarbital, methotrexate, aspirin
- trapped in basic environments
- treat overdose with bicarbonate
what are weak base drugs?
where do they get trapped?
how do you treat overdose?
- amphetamines
- trapped in acidic environments
- treat overdose with ammonium chloride
what are phase 1 types of drug metabolism?
what enzyme do they require?
what do they yield?
what occurs in geriatric patients?
- reduction, oxidation, hydrolysis
- require cytochrome P 450
- yield slightly polar, water soluble metabolites
- geratric patients lose phase I first
what are phase 2 type of drug metabolism?
what do they yield?
- conjugation–Methylation, Glucuronidation, Acetylation, Sulfation
- geriatric patients have More GAS (phase 2)
- yields very polar, inactive metabolites (renally excreted)
what occurs in patients who are slow acetylators?
- have increased side effects from certain drugs b/c of decreased rate of metabolism
effect of competitive antagonist on receptor binding
- shifts curve right (decreased potency)
- no change in efficacy
- can be overcome by increasing the concentration of agonist substrate

effect of noncompetitive antagonist on receptor binding
- shift curve down (decrease efficacy)
- cannot be overcome by inc agonist substrate concentration

effect of partial agonist (alone) on receptor binding
- acts at same site as full agonist, but with lower maximal effect (dec efficacy)
- potency is an independent variable

what is the therapeutic index?
- measurement of drug safety
-
Therapeutic Index = TD50/ED50 = median toxic dose / median effective dose
- TITE
- safer drugs have higher TI values
- drugs with lower TI values frequently require monitoring
- therapeutic window–dosage range that can safely and effectively treat dz

alpha 1 receptor:
type of receptor
G protein class
major functions
- sympathetic
- q
- functions:
- inc vascular smooth muscle contraction
- inc pupillary dilator muscle contraction (mydriasis)
- inc intestinal and bladder sphincter muscle contraction
alpha 2 receptor:
type of receptor
G protein class
major functions
- sympathetic
- i
- functions:
- dec sympathetic (adrenergic) outflow
- decrease insulin release
- dec lipolysis
- inc platelet aggregation
- dec aqueous humor product
beta 1 receptor
type of receptor
G protein class
major functions
- sympathetic
- s
- functions:
- inc heart rate
- inc contractility
- inc renin release
- inc lipolysis
beta 2 receptor:
type of receptor
G protein class
major functions
- sympathetic
- s
- functions:
- vasodilation
- bronchodilation
- inc lipolysis
- inc insulin release
- dec uterine tone (tocolysis)
- ciliary muscle relaxation
- inc aqeuous humor production
beta 3 receptor:
type of receptor
G protein class
major functions
- sympathetic
- s
- functions:
- inc lipoysis
- inc thermogenesis in skeletal muscle
M1 receptor
type of receptor
G protein class
major functions
- parasympathetic
- q
- functions:
- CNS
- enteric nervous system
M2 receptor
type of receptor
G protein class
major functions
- parasympathetic
- i
- functions:
- dec heart rate
- dec contractility of atria
M3 receptor
type of receptor
G protein class
major functions
- parasympathetic
- q
- functions:
- inc exocrine gland secretions
- lacrimal, sweat, salivary, gastric acid
- inc gut peristalsis
- inc bladder contraction
- bronchoconstriction
- inc pupillary sphincter muscle contraction (miosis)
- ciliary muscle contraction (accommodation)
- inc exocrine gland secretions
D1 receptor
type of receptor
G protein class
major functions
- dopamine
- s
- functions:
- relaxes vascular smooth muscle
D2 receptor:
type of receptor
G protein class
major functions
- dopamine
- i
- functions:
- modulate transmitter release, especially in brain
H1 receptor:
type of receptor
G protein class
major functions
- histamine
- q
- functions:
- inc nasal and bronchial mucus production
- inc vascular permeability
- contraction of bronchioles
- pruritus
- pain
H2 receptor:
type of receptor
G protein class
major functions
- histamine
- s
- functions:
- increase gastric secretion
V1 receptor:
type of receptor
G protein class
major functions
- vasopressin
- q
- functions:
- inc vascular smooth muscle contraction
V2 receptor:
type of receptor
G protein class
major functions
- vasopressin
- s
- functions:
- inc water permeability and reabsorption in collecting tubules of kidney
- “V<strong>2</strong> is found in 2 kidneys”
- inc water permeability and reabsorption in collecting tubules of kidney
how to remember G protein linked 2nd messengers
“After qisses (kisses), you get a qiq (kick) out of siq (sick) sqs (super kinky sex).

tyramine–mechanism
- normally degraded by monoamine oxidase (MAO)
- levels inc in patients taking MAO inhibitors who ingest tyramine rich foods (ie. cheese, wine)
- excess tyramine enters presynaptic vesicles and displaces other neurotransmitters (ie. NE) –> inc active presynaptic neurotransmitters –> inc diffusion of neurotransmitters into synaptic cleft –> inc sympathetic stimulation
what does tyramine classically cause?
hypertensive crisis
name the 4 direct cholinomemetic agonists
- bethanechol
- carbachol
- methacholine
- pilocarpine
bethanechol–mechanism
- activates bowel and bladder smooth muscle
- resistant to AChE
- “Bethany call (bethanchol) me to activate your bowels and bladder.”
bethanechol–use
- postoperative ileus
- neurogenic ileus
- urinary retention
carbachol–mechanism
- carbon copy of acetylcholine
carbachol–use
- constricts pupil and relieves intraocular pressure in open angle glaucoma
methacholine–mechanism
- stimulates muscarinic receptors in airway when inhaled
methacholine–use
- challenge test for diagnosis of asthma
pilocarpine–mechanism
- contracts ciliary muscle of eye–open angle glaucoma
- pupillary sphincter–closed angle glucoma
- resistant to AChE
- “You cry, drool, and sweat on your pilow”
pilocarpine–use
- potent stimulator of sweat, tears, saliva
- open angle and closed angle glaucoma
- xerostomia–Sjorgren syndrome
name the 7 indirect cholinomimetic agents (anticholinesterases)
- donepezil
- galantamine
- rivastigmine
- edrophonium
- neostigmine
- physostigmine
- pyridostigmine
donepezil, galantamine, rivastigmine–mechanism
- inc ACh
donepezil, galantamine, rivastigmine–use
- Alzheimer disease
edrophonium–mechanism
- inc ACh
edrophonium–use
- historically, diagnosis of myasthenia gravis–extremely short acting
- myasthenia now diagnosed by anti AChR Ab (anti acetylcholine receptor antibody) test
neostigmine–mechansm
- inc ACh
- “Neo CNS = No CNS penetration (quaternary amine)
neostigmine–use
- postoperative and neurogenic ileus and urinary retention
- myasthenia gravis
- reversal of neuromuscular junction blockade–postoperative
physostigmine–mechanism
- inc ACh
- “Physostigmine ‘phyxes’ atropine overdose”
physostigmine–use
- anticholinergic toxicity
- crosses blood brain barrier –> CNS (tertiary amine)
pyridostigmine–mechanism
- inc ACh
- inc muscle strength
pyridostigmine–use
- myasthenia gravis (long acting)
- “Pyridostigmine gets rid of myasthenia gravis”
- does not penetrate CNS–quaternary amine
what is important to watch for when administering any cholinomimetic agents?
- exacerbation of COPD
- asthma
- peptic ulcers
what causes cholinesterase inhibitor poisoning?
- often due to organophosphates, such as parathion, that irreversibly inhibit AChE
in which population is cholinesterase inhibitor poisoning usually seen and why?
- farmers b/c organophosphates are often components of insecticides
what does cholinesterase inhibitor poisoning cause?
- Diarrhea
- Urination
- Miosis
- Bronchospasm
- Bradycardia
- Excitation of skeletal muscle and CNS
- Lacrimation
- Sweating
-
Salivation
- “DUMBBELSS”
- may lead ot respiratory failure if untreated
what is the antidote for cholinesterase inhibitor poisoning?
- atropine (competitive inhibitor) + pralidoxime (regenerates AChE if given early)
name the muscarinic antagonists
- atropine, homatropine, tropicamide
- benztropine
- glycopyrrolate
- hyoscyamine, dicyclomine
- ipratropium, tiotropium
- oxybutynin, solifenacin, tolterodine
- scopolamine
atropine, homatropine, tropicamide–organ system and use
- eye
- produce mydriasis
- produce cyclopegia
benztropine–organ system and use
- CNS
-
Parkinson dz
- “park my Benz”
- acute dystonia
-
Parkinson dz
glycopyrrolate–organ system and use
- GI
- drooling
- peptic ulcer
- respiratory
- preoperative use to reduce airway secretions
hyoscyamine, dicyclomine–organ system and use
- GI
- antispasmodics for irritable bowel syndrome
ipratropium, tiotropium–organ system
- respiratory
- COPD
- asthma
- “I pray I can breathe soon”
oxybutynin, solifenacin, tolterodine–organ system and use
- genitourinary
- reduce bladder spasms
- urge urinary incontinence
- overactive bladder
scopolamine–organ system and use
- CNS
- motion sickness
atropine–drug class and use
- muscarinic antagonist
- used to treat bradycardia and for ophthalmic applications
what is the action of atropine on the eyes?
- increase pupil dilation
- cycloplegia
what is the action of atropine on the airway?
- decreased secretions
what is the action of atropine on the stomach?
- decreased acid secretion
what is the action of atropine on the gut?
- decrease motility
what is the action of atropine on the bladder?
- decreased urgency in cystitis
atropine and cholinesterase inhibitor poisoning
- blocks DUMBBeLSS in cholinesterase inhibitor poisoning
- diarrhea
- urination
- miosis
- bronchospasm
- bradycardia
- lacrimation
- sweating
- salivation
- DOES NOT block excitation of skeletal muscle and CNS
- mediated by nicotinic receptors
atropine–toxicity
- incresed body temperature–due to dec sweating
- rapid pulse
- dry mouth
- dry, flushed skin
- cycloplegia
- constipation
-
disorientation
- “Hot as a hare”
- “Dry as a bone”
- “Red as a beet”
- “Blind as a bat”
- “Mad as a hatter”
- can cause acute angle closure glaucoma in elderly due to mydriasis
- can cause urinary retention in men with prostatic hyperplasia
- can cause hyperthemia in infants
name the direct sympathomimetics
- albuterol, salmeterol
- dobutamine
- dopamine
- epinephrine
- fenoldopam
- isoproterenol
- midocrine
- norepinephrine
- phenylephrine
albuterol, salmeterol–mechanism
- beta 2 > beta 1
albuterol, salmeterol–use
- albuterol for acute asthma or COPD
- salmeterol for long term asthma or COPD control
dobutamine–mechanism
- beta 1 > beta 2, alpha
dobutamine–use
- heart failure (HF) – inotropic > chronotropic
- cardiac stress testing
dopamine–mechanism
- D1 = D2 > beta > alpha
dopamine–use
- unstable bradycardia
- HF
- shock
- inotropic and chronotropic effects at lower doses due to beta effects
- vasoconstriction at high doses to alpha effects
epinephrine–mechanism
- beta > alpha
epinephrine–use
- anaphylaxis
- asthma
- open angle glaucoma
- alpha effects predominate at high doses
- significantly stronger effect at beta2 receptors than norepinephrine
fenoldopam–mechanism
- D1
fenoldopam–use
- postoperative hypertension
- hypertensive crisis
- vasodilator–coronary, peripheral, renal, splanchnic
- promotes natriuresis
fenoldopam–toxicity
- hypotension
- tachycardia
isoproterenol–mechanism
- beta1 > beta2
isoproterenol–use
- electrophysiologic evaluation of tachyarrhythmias
- can worsen ischemia
midodrine–mechanism
- alpha1
midodrine–use
- autonomic insufficiency
- postural hypotension
midodrine–toxicity
- may exacerbate supine hypertension
norepinephrine–mechanism
- alpha1 > alpha2 > beta1
norepinephrine–use
- hypotension
- septic shock
phenylephrine–mechanism
- alpha1 > alpha2
phenylephrine–use
- hypotension (vasoconstrictor)
- ocular procedures (mydriatic)
- rhinitis (decongestant)
name the indirect sympathomimetics
- amphetamine
- cocaine
- ephedrine
amphetamine–mechanism
- indirect general agonist
- reuptake inhibitor
- releases stored catecholamines
amphetamine–use
- narcolepsy
- obesity
- ADHD
cocaine–mechanism
- indirect general agonist
- reuptake inhibitor
cocaine–use
- causes vasoconstriction and local anesthesia
what to remember about cocaine intoxication?
- never give beta blockers
- can lead to unopposed alpha1 activation and extreme hypertension
ephedrine–mechanism
- indirect general agonist
- releases stored catecholamines
ephedrine–use
- nasal decongestion
- urinary incontinence
- hypotension
norepinephrine vs. isoproterenol
- norepinephrine inc systolic and diastolic pressures as a result of alpha1 mediated vasoconstriction –> inc mean arterial pressure –> reflex bradycardia
- isoproterenol–not commonly used anymore
- has little alpha effect but causes beta2 mediated vasodilation –> dec mean arterial pressure and inc heart rate thru beta1 and reflex activity

name the sympatholytics alpha2 agonists
- clonidine, guanfacine
- alpha methyldopa
clonidine, guanfacine–use
- hypertensive urgency (limited situations)
- ADHD
- tourette syndrome
clonidine, guanfacine–toxicity
- CNS depression
- bradycardia
- hypotension
- respiratory depression
- miosis
alpha methyldopa–use
- hypertension during pregnancy
alpha methyldopa–toxicity
- direct Coombs + hemolysis
- SLE like syndrome
name the non-selective alpha blockers
- phenoxybenzamine (irreversible)
- phentolamine (reversible)
phenoxybenzamine–use
- pheochromocytoma (used preoperatively) to prevent catecholamine (hypertensive) crisis
phenoxybenzamine–toxicity
- orthostatic hypotension
- reflex tachycardia
phentolamine–use
- give to patients on MAO inhibitors who eat tyramine containing foods
phentolamine–toxicity
- orthostatic hypotension
- reflex tachycardia
name the alpha1 selective alpha blockers
- -osin ending
- Prazosin, terazosin, doxazosin
- tamsulosin
Prazosin, terazosin, doxazosin–use
- urinary symptoms of BPH
- PTSD–prazosin
- hypertension
Prazosin, terazosin, doxazosin–toxicity
- 1st dose orthostatic hypotension
- dizziness
- headache
tamsulosin–use
- urinary symptoms of BPH
tamsulosin–toxicity
- 1st dose orthostatic hypotension
- dizziness
- headache
name the alpha2 selective alpha blockers
- mirtazapine
mirtazapine–use
- depression
mirtazapine–toxicity
- sedation
- inc serum cholesterol
- inc appetite
alpha blockade of epinephrine vs. phenylephrine
- effects of an alpha blocker like phentolamine on blood pressure responses to epinephrine and phenylephrine
- epinephrine response exhibits reversal of the mean blood pressure change, from a net inc (alpha response) to a net decrease (beta 2 response)
- the response to phenylephrine is suppressed but not reversed b/c phenylephrine is a “pure” alpha agonist w/o beta action

name the beta blockers
- acebutolol
- atenolol
- betaxolol
- carvedilol
- esmolol
- labetalol
- metoprolol
- nadolol
- nebivolol
- pindolol
- propranolol
- timolol
beta blockers–use
- angina pectoris
- MI
- SVT (metoprolol, esmolol)
- hypertension
- HF
- glaucoma (timolol)
- variceal bleeding (nadolol, propranolol)
how do beta blockers work for angina pectoris?
- dec heart rate and contractility
- results in dec O2 consumption
how do beta blockers work for MI?
- dec mortality
how do beta blockers work for SVT?
- only metoprolol, esmolol
- dec AV conduction velocity
- class II antiarrhythmic
how beta blockers work for hypertension?
- dec cardiac output
- dec renin secretion
- due to beta1 receptor blockade on JGA cells
how do beta blockers work for HF?
- dec mortality
- with bisoprolol, carvedilol, metoprolol
how do beta blockers work for glaucoma?
- only timolol
- dec secretion of aqueous humor
how do beta blockers work for variceal bleeding?
- only nadolol, propranolol
- dec hepatic venous pressure gradient and portal hypertension
beta blockers–toxicity
- erectile dysfunction
- cardiovascular adverse effects–bradycardia, AV block, HF
- CNS adverse effects–seizures, sedation, sleep alterations
- dyslipidemia
- with metoprolol
- asthma/COPD exacerbations
beta blockers and cocaine users
- use with caution in cocaine users due to risk of unopposed alpha-adrenergic receptor agonist activity
beta blockers and diabetics
- despite theoretical concern of masking hypoglycemia in diabetics, benefits likely outweight the risks
- NOT contraindicated
name the beta1 selective antagonists (beta1 > beta2)
- acebutolol–partial agonist
- atenolol
- betaxolol
- esmolol
-
metoprolol
- “selective antagonists mostly go from A to M–beta<strong>1</strong> with 1st half of alphabet”
name the non selective antagonists (Beta1 = beta2)
- Nadolol
- Pindolol–partial agonist
- Propranolol
-
Timolol
- Nonselective antagonists mostly go from N to Z–beta<strong>2</strong> with 2nd half of alphabet
name the nonselective alpha and beta antagonists
- carvedilol
- labetalol
- both have modifed suffixes–instead of “-olol”
nebivolol–selectivity
- combines cardiac selective beta1 adrenergic blockade with stimulation of beta3 receptors which activate nitric oxide synthase in the vasculature
name the 3 ingested seafood toxins
- tetrodotoxin
- ciguatoxin
- histamine–scombroid poisoning
tetrodotoxin–source
- pufferfish
tetrodotoxin–mechanism
- highly potent toxin
- binds fast voltage gated Na channels in cardiac/nerve tissue
- prevents depolarization
tetrodotoxin–symptoms
- nausea
- diarrhea
- paresthesias
- weakness
- dizziness
- loss of reflexes
tetrodotoxin–treatment
mostly supportive
ciguatoxin–source
- reef fish such as barracuda, snapper, moray eel
ciguatoxin–mechanism
- opens Na channels which causes depolarization
ciguatoxin–symptoms
- symptoms mimic cholinergic poisoning
ciguatoxin–treatment
primarily supportive
histamine (scombroid poisoning)–source
- spoiled dark meat fish such as tuna, mahi mahi, mackerel, bonito
histamine (scombroid poisoning)–mechanism
- bacterial histidine decarboxylase converts histidine to histamine
- frequently misdiagnosed as a fish allergy
histamine (scombroid poisoning)–symptoms
- mimics anaphylaxis:
- acute burning sensation of mouth
- flushing of face
- erythema
- urticaria
- itching
- may progress to:
- bronchospasm
- angioedema
- hypotension
histamine (scombroid poisoning)–treatment
- antihistamines
- albuteral and epinephrine if needed