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First Pass Metabolism
destroyed before gets to target system by enzymes in GI tract. If survives --> liver where gets metabolized. Ex=AMINOGLYCOSIDES (insulin)=why no oral admin yet
first pass metabolism (aka presystemic metab)
the fraction of drug lost in liver or gut wall
Ex=propranolol, lidocaine (arythmia), nitrates (angina)
oral-->metab by bacteira w/glucuronidase-->absorbed in SI-->into liver via portal vein-->GLUCORONIDATION here-->through bile duct-->back into SI-->metab again etc...
Example of enterohepatic circulation?
BC pills: bact in that intest metab & help w/enterohepatic circulation. If on abx, bact can't break down bc pills= lowers processing of them, gets excreted instead of metabolized =BABY.
-no first pass metabolism
-directly into submand vein, then sup vena cava, then heart w/i minutes
-Lower rectum=direct link to syst circulation
-Upper rectum=direct to liver
-About 50% bipasses liverthrough lower rectum, still better
-Smooth plasma , no spikes like when take in am, pm etc...
-no first pass metabolism
-Probs? poss tolerance so must remove 8-10hrs
-alveolar epothelium huge SA for lipid sol drugs
-rapid action b/c huge blood supply
-mild irritant drugs ok
IMPT: of on anti-coag drugs like hep, don't give IM b/c=hamartoma!!!!
-insulin & heparin, self-admi is poss
-prob inj insulin IM is that if work out, get lots blood to that m, then get huge insulin rel=low bp=bad
What is pharmokinetics?
-effects of pH on absorption of drug
-only non-ionized are lipid sol and can cross cell membrane
-ionized are water sol no cross memb, gets peed out
Weak acids & weak bases?
-drugs either weak acids or weak bases, strong acids & bases not used b/c always protonated thus dont' cross memb
-form changes based on surrounding pH
HA <--> H+ + A- = weak acid, a proton donor
BH+ <--> H+ + B = base, accepts proton
What do you want to do if get acidic drug poisioning (acetominaphin)?
make urine alkaline, drug gets ionized, then excreted
What effect does pH have on ionization of a drug?
-weak acids become ionized as pH goes up, or as the pH-pKa gest more positive (in a more basic medium)
-weak bases become ionized as pH decr or as pH-pKa gets more negative (in an acidic env)
What's the equation for Bioavailability?
Fraction of drug reaching systemic circulation
F=fg X (1-ER)
1-ER=amnt escap 1st pass metab
What must 2 drugs have in common to be BIOEQUIVALENT?
1) Same Cmax (max plasma  attained by drug)
2) Same Tmax (time at which max  is reached)
...they must reach same plasma  at same time w/i 20% margin
What is volume of distribution equation?
Vd = D/Co
D=total amt of drug in body
Co=drug  in plasma
Note: loading dose dep on vol, maint dose dep on clearance
What are the general Vd's of our body spaces?
11L=ecf (like mannitol can't penetrate cell walls)
42L=total body water (ecf & icf...alcohol)
>42L=w/i cells or tissues
Note: babies have high high total body water, old people have least, women have less then men, which affects dosing
What do acidic drugs bind?
Acidic = albumin (b/c slightly basic)
Basic = glycoproteins (b/c acidic)
-Plasma protein bound drugs can not leave vascular compartments & aren't free to be used if bound
What's the danger w/giving sulfonamides to babies?
It displaces bilirubin from binding sites can cause jaundice and kernicterus problems. ALSO it displaces some of the WARFARIN bound to proteins=more avail and free=BLEEDING PROBS!
What does phase 1 & 2 metabolism phases do?
Phase 1-uses cytochrome p450
Phase 2-conjugate rxn, adds water sol molecule so can be excreted
What factors do you need to know to predict whether drug is in ionized or un-ionized form? Q
1) acid/basic nature of the drug
2) pKa of the drug
3) pH of the surrounding
2)Active metabolite from inactive drug example?
3)Active metabolite from active drug ex?
1)what happens w/metabolism usually
2)L-Dopa-->dopa & Enalapril-->enalaprilat
3)Codeine-->morphine & imipramine-->desipramine
What drugs induce/help CPY450 enzyme?
st john's wort
What's the deal w/ abscence of cytochrome P450 2D6 in some caucasians?
can't convert codeine to morphine, get little if any pain relief from codeine
...rem: some east african's have hyperactive cyto P450 so they can OD on codeine be careful!!
If you want to excrete an acidic drug, what do you do? "ASAP"
Make urine basic (alkaline)
Use: sodium bicarb, potassium citrate & acetazolamide
If you want to excrete a basic drug, what do you do?
Make urine acidic
Use:ammonium chloride, vit-C, cranberry juice
What is FIRST ORDER KINETICS?
-rate of elim proportional to plasma  of drug
-follows same order of breakdown over time:
-most drugs are 1st order kinetics
-all amounts  taper off at same place b/c dep on 1/2 life NOT how much you give them. Remember:steady state dep solely on 1/2 life
What is the time to reach a steady state dependent on?
only on drug's 1/2 life NOT on dose size or freq of administration
we want drugs to be at steady state in body
Time & Steady State?
-50% steady state reached at 1 1/2 life, at 1st dose
-75% at 2 1/2 lifes, at 2nd dose
-90% at 3.3 1/2 lifes
-96.85% of steady state reached at 5 1/2 lifes. THIS WHERE WE CONSIDER THEM AT A STEADY STATE, WHAT WE GIVE THEM IS WHAT COMES OUT
Does rate of infusion of drug affect time to reach steady state?
NO! b/c ss only dep on drug's 1/2 life HOWEVER, if rate of infusion is doubled, then plasma level of drug at SS is doubled
...time to reach SS always same b/c 1/2 life det it, it's the  that changes!!
What is the definition for clearance?
vol of plasma that is completely cleared of drug in a given time
Clearance=rate of elim/plasma drug 
How do you calculate for a corrected dose based on P w/say kidney disease or decreased clearance?
Corrected dose=avg dose per day X patients CL/normal CL
Loading dose equation?
maint dose X 2
...loading dose brings us right up to theraputic rance w/out waiting
What is the problem with a narrow theraputic range & what are the drugs w/this?
harder to manage, to keep w/i small range
What is a receptor?
drug binds here, produces an effect
-propagates signal to inside of cell
-adapt , if body wants to reduce effect of drug, can down regulate R's (see w/long term use of drug...TOLERANCE)
Definition of affinity?
drug bind to R, how STRONG drug binds R has nothing to do with activating anything
What is intrinsic activity?
ability of drug to activate it's R & prod response...once bound, how can you or can you activate the R
What is an AGONIST?
Binds to R & activates it...produces a response
an agonist has both affinity & intrinsic activity
What is a PARTIAL AGONIST?
binds & activates R, but produces sub-maximal response when compared to agonist., it competitively antagonizes the pure agonist
What are examples of intra-nuclear R's?
-steroids, thyroxine, Vit-D
-must be lipid sol to cross membrane
-involves synth of proteins, takes days
What is potency?
-amount of drug needed to produce the desired response
-on graph, closer to Y axis=most potent
What is theraputic index?
-ratio of median lethal dose (LD50) to median effective dose (ED50)
-low therapeutic index=bad drugs, not a lot of room to play to find good dose
What is a physiologic antagonist?
-binds to different receptor & produces opposite effect of the drug it's antagonizing...different R's & opposite effects
-Ex: histamine binds to R & vasodilates & bronchoconstricts. Epinephrine=it's physiologic antagonist, it binds DIFFERENT Beta R and causes bronchodilation and alpha R & causes vasoconstriction
-Proprinolol poisioning: bind beta R=bradycardia, treat by stimul glucagon R=incr heart contraction
What is a competitive/reversible antagonist?
-decr potency NOT EFFICACY
-see parallel shift of DRC to R
What is a non-competative/irreversible antagonist?
-binds R irreversibly or it binds to a different site than the agonist
-see non-parallel shift in DRC to R
Examples of non-competative drugs?
-proton pump inh
-phenoxybenzamine for pheochromocytoma
Focus more on drugs inducing/inhibiting cyt p450
How to make urine more acidic or alkaline?
1st and 0 order kinetics
Know the 0 order drugs
Maintenance dose is dependent on CL
Vd formula? Used to calculate loading dose
Know maintenance dose formula
Loading dose formula
Half life 2 formulas
Have to know when drug reaches steady state and time to reach it
Therapeutic index of drug
What are spare receptors?
-R's that exist if max drug response can be obtained w/ out using all R's. See non-linear rel between R occupancy & response on graph (linear rel when no spare R's)
What decreases w/ an irreversible noncompetative antagonist?
only efficacy!, but w/super high dose, both efficacy & potency decrease on DRC
In old people, is Phase 1 or Phase 2 reactions lost most?
-Phase 1 lost when liver starts to loose function.
-Lorazipam only metabolized by phase 2 conjugation reactions, so best to use these types drugs w/old folks.
What is R sensitization or Up-regulation?
-prolonged use of R blocker=body senses & up regulates more R;s
-Ex=beta blockers, so if all sudden stop taking beta blocker's, now have tons extra R's NE acts on all of them=tachycardia!!!!
What are the 3 phases of drug development clinical trials?
Phase 1-give to healthy P, test for side-effects tests for safety
Phase 2-give to small amt of people does it work?
Phase 3-give to bigger # of people simulates regular use in larger population
What are the 5 categories for teratogenicity?
A=folic acid safe
B=no evidence of risk
D=Bad, evidence of risk
E=Super bad, deff risk thalidomide
Where do the SNS & PNS start?
-also know SNS has diffuse action, affects many organs
-short pre-gangli, long post-ganglia
-Ex: Ach rel onto adrenal medulla-->causes rel Epi (major one) NE (minor one, becomes major in pheochromocytoma)!!
-long pre-ganglionic, short post ganglionic on organ it's affecting
How is PNS Ach synth, what R's does it act on, what causes it's release & how is it inactivated?
-Synth by acetyltransferase (ChAT)
-Acts on both nicotinic & muscarinic R's
-Ca is influxed-->vesicle w/Ach released
-Inactivated by acetyl cholinesterase in synaptic cleft. most impt way it's destroyed super fast in miliseconds. This enzyme inhibitor is a major class of drugs
...remember Ach made from choline & acetyl CoA & is recycled after broken down & transported back into axon to be used again
What are the 2 types of acetyl cholinesterase & where are they located?
-Acetyl cholinesterase (true)-at all neuromuscular jncts, hydrolizes Ach only
-Butyryl cholinesterase (pseudo)-in plasma & liver, hydrolizes procaine (local anisthetic) & succinylcholine AKA suxamethonium
What are the 2 major types of Ach muscarinic R's and where are they?
-M2:heart, causes decr adenyl cyclase, decr cAMP, K channel opens, K in, hyperpolarize, decr HR
-mimics vagal activity
-causes decr in heart contraction (even though will incr HR w/ low dose)
-M3:Everywhere, causes incr PLC, incr IP3 & DAG, ca enters cell, rel of vessicles w/NT
-on BV's, causes vasodilation via NO
-respiratory tract, causes bronchoconstriction & increase in secretions
How does Ach cause vasodilation?
binds M3 R, causes rel NO, acts on cGMP=vasodilation via smooth m relaxation
What R does Ach bind to & what does it do in the GI tract?
-binds M3 R
-increases tone, peristalsis,secretions & relaxes sphincter
What R does Ach bind in urinary bladder & what does it do?
-binds M3 R
-contracts detrusor & relaxes trigone & spincter
What R does Ach bind in eye & what does it do?
-binds M3 R
-on sphincter M, pupil constriction
-causes accommodation: ciliary m's contract, susp lig relax, lense conves = near vision
-to see something far away, cilliary m's relax, lense flattens
What is parasympathetic control of accomodation?
-relaxed cilliary m=flat lense=see distant object
-contract cilliary m=convex, thick, round lense=near vision
What are the major cholinergic agonists & what kind of affects do they have?
-Ach, methacholine, carbachol, bethanechol, cevimeline, pilocarpine
-diffuse effects so many actions all over act on both nicotinic & muscarinic R's
What are the nicotinic partial agonists & why are these good?
-varenicline "chantix" smoking cessation
-good b/c in the presence of a full agonist nicotine, they act as antagonists. Keeps R turned on at low level so body thinks nicotine coming in
What are irreversible anti-AchE agents?
-dytios tight binding to AchE for lifetime, but early on can still hydrolize the bond before covalent bonding happens=can reverse if super early in rxn.
What are reversible (carbamate) anti-AchE agents?
-Carbaryl (Sevin) BAD
What kind of drug is edrophonium & what's it used for?
-myasthenia gravis, works for 5-15 min
What's neostigmine & what's it used for?
-reversible anti-AchE, doesn't enter CNS b/c quaternary amine
-myasthenia gravis, works for 1-2 hrs
-bad oral absorption
What's physostigmine & what's it used for?
-reversible anti-AchE lipid sol, enters CNS
-glaucoma, or atropine poisioning,works for 1-2 hours
-good oral absorption
How do irreversible Anti-AchE agents work?
-organophosphorous compounds react w/esteric site of enzyme, which is then hyrolized very slow or not at all
-over time AchE ages by losing one alkyl group and eventually becomes totally resistant to hydrolysis=permanent
What is the cholinesterase reactivator & what's it used for?
-PAM!!! (pralidoxime), attaches to anionic site of AchE if there's also organophosphorous agent there & releases the enzyme
-nerve gas & organophosphorus poisioning
-don't use for OD of neostigmine OR other carbamate poisioning
What do you use for tx of organophosphate instecticide poisioning?
ATROPINE BABY!!!, it blocks muscarinic R's!!! AKA it's ANTI-MUSCARINIC or PARASYMPATHOLYTIC
What do you use to treat glaucoma besides physostigmine?
-carbachol - cholinomimetic (Ach like)
-pilocarpine -" "
What do you use for paralysis/atony of bladder or GI like after Sx?
-neostigmine = best -" "
What's good to use for OD of tricyclic anti-depressants (TCA's) or anti-muscarinic agents?
What would you give a p after general anesh to recover from blockage of nicotinic R's of skeletal m while being on ventilator?
-neostigmine (cholinomimetic) ...BUT it will increase Ach levels EVERYWHERE so must give small dose of atropine w/it don't get bradycardia.
What can you use to treat alzheimers?
-galantamine -" "
-rivastigmine - " "
-tacrine - " '
In the SNS, how are Ne & Epi degraded usually?
Re-uptake . Ne & Epi take lots of energy to make, so don't want to degrade it like Ach in the PNS.
Where is AchE located?
What about Butyryl Cholinesterase?
-in all neuromuscular junctions
-like AchE, in plasma & liver. Hydrolyzes procaine (local anisth) & succinylcholine (suxamethonium)
How does Botulinum toxin block rel of Ach?
-degrades SNAP-25 that's req for vessicle fusion & rel of Ach
How do we metabolize catecholameines (NE)?
-MAO: acts on NE after it's taken back into axoplasm via NET
-COMT: acts on NE after goes into circulation, mostly in LIVER
What are the 2 types of MAO reuptakes & where are they located?
-MAO A: anywhere in body
-MAO B: Brain
What are the MAO A inhibitors (keeps catacholamines in cleft longer)?
What's the "cheese reaction"?
If on a MAO inhibitor, you're inhibiting MAO in the GI tract too. Tyramine (a catecholamine) is in wine & cheese, it you inhibit MAO, you can't metabolize tyramine, it builds up & enters CNS & nerves & promotes the release of NE=super high amounts of NE--> hypertension & possible stroke
Where are MAO B inhibitors located, & what do they metabolize?
-selegiline & rasagiline
-metabolize dopamine, norepi & 5-HT
good parkinsons tx
Where are M2 (Gi) PNS r's & what do they do?
-decr AC, cAMP, opens K+ ch=hyperpolarize & decr HR
Where are M3 (Gq) PNS r's & what do they do?
-incr PLC, IP3 & DAG=let Ca in
-have all expected PNS effects on organs
eye:constr pupil via sphincter m
Where are A1 (Gq) SNS r's & what do they do?
-Eye: contr radial fibers=mydriasis
-Arterioles/veins: contr=incr BP
-Bladder: contract trigone=urinary retention don't give w/BPH already hard to Pee
Where are A2 (Gi) SNS R's & what do they do?
-decr AC & cAMP
-platelet aggregation & pancreas decr insuin rel
-decr NE rel
Where are B1 (Gs) SNS R's & what do they do?
-incr cAMP, PKA = let ca in
-heart, contr cardiac m
-kid, incr renin rel
Where are B2 (Gs) SNS R's & what do they do?
-incr cAMP, PKA=let Ca in
-dilate BVs to skel m, see tremor
-inhibit MLK in smooth m=decr contraction, thus causing vasodilation
Where are Dopa 1 SNS R's & what do they do?
-stimulate AC & cAMP
-vasodilate renal veain= inr blood flowgood in shock saves kidney
Where are Dopa-2 (Gi) SNS R's & what do they do?
-inhibit AC, decr cAMP, open K+ channels=hyper polarize
What is prazosin (minipress) & what is it used for?
-reversible selective a-1 blocker
-tx for HT & BPH urinary retention
...give first low dose at bed so don't get postural hypotension b/c of FIRST DOSE PHENOMENON
What is phenoxybenzamie & what's it used for? What must you also use w/it and why?
-irrevers nonselective a-blocker
-tx for PHEOCHROMOCYTOMA...(rem that cause incr. rel NE & Epi, need to block both those to treat it, so must also give b-blocker.
...GIVE A-BLOCKER 1ST THEN B if use B 1st get severe hypertensive crisis & stroke
What are B-blockers used for?
What is the 1 situation where you wouldn't use them?
-In every cardiovascular problem & hypertension
EXCEPT Prinzmetal's Angina (a vasospastic angina at rest)
What are the ABCS's of beta blockers (adverse effects*?
AV block, bradycardia
Bronchial asthma and COPD
What are the uses of B-blockers?
-hypertension b/c decreases CO & thus resistance
-CCF, low dose in mild & moderate cases
-Glaucoma (one of the best types of drugs for this)
-Hyperthyroidism (treats palpatations & tremors from this)
-Prev esoph varacies in portal HT/chirrhosis
What's the "Black Box Warning" for B-blockers?
must taper dosage down and gradually pull P off it over 1-2 weeks don't stop suddenly!!!
If not can get angina pectoris and MI if don't
What are ganglionic blockers and what effects do they produce?
-competative antagonists against nicotinic r's in autonomic ganglia
-decrease PNS effects EXCEPT in ARTERIOLES, VEINS & SWEAT GLANDS will decr SNS effects!
What affect does Ganglionic blockers have in atrerioles/veins & sweat glands?
-wellll here they will block SNS effects (block PNS effects everywhere else)
-arterioles/veins if block SNS effect see vasodilation
-sweat glands=if block SNS effects see anhydrosis
What's chronic simple glaucoma & what's it due to?
-b/c of increased production of aqueous humor
-therapy aims to decrease this production
What are the 4 types of drugs to treat glaucoma?
1) beta blockers, decr form of aq humor by decreasing cAMP watch out for bronchospasm in asthmatics
2) alpha-2 agonists, " "
3) carbonic anhydrase inh, " "
4) cholinomimetics, incr outflow by effecting ciliary & sphincter m's (but low choice b/c this usually isn't the prob w/glaucoma
What are the effects of PROPRANOLOL beta blocker on the heart?
-neg ionotropic effects, so decr contration
-neg chronotropic action, so decr HR-->longer diastole=better blood flow
-decr AV conduction, good for A-fib
What are the effects of PROPRANOLOL beta blocker on the eye?
-glaucoma TX best choice!! b/c decr aqueous humor production
What are the effects of PROPRANOLOL beta blocker on the respiratory tract?
-causes bronchoconstriction so don't use in asthma or COPD p's!!!!! If must use, use B1 selective one (b/c remember B2's are in the bronchioles)
What are the metabolic side-effects of PROPRANOLOL beta blocker?
-blocks hypogycemia warning signals, so in DM P, use B1 selective one BUT if DM p has MI, benefits outweigh the risks here
Accommodation is purely under PNS CONTROL, so involves only M3 R's thus only muscarinic drugs can affect accommodations.
-If use muscarinic agonist get contr ciliary M and get blurry vision b/c focusing for near objects.
-If block muscarinic Ach R's then can't accomodate, can't see near, can only see far.
BLURRY VISION=MUSCARINIC DRUG!
Does an alpha blocker affect accommodation?
NO NO NO NO NO!!! how you can tell it's alpha blocker & not M3 agonist!
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