USMLE 1 Pharm basics
Terms
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- amount of drug in body/_______ = Vd
-
plasma drug concentration
(Vd is Volume of Distribution) - rate of elimination of drug/[plasma drug] = ?
- CL (Clearance)
- (.7)(Vd)/CL = ?
- T 1/2
- A drug infused at a constant rate reaches about 94% of steady state after _______ t 1/2s.
- 4
- A loading dose is calculated using this formula.
-
Loading Dose = (Cp)(Vd)/F
(Cp = target plasma conc; F = bioavailability) - A maintenance dose is calculated using this formula.
-
(Cp)(CL)/F
(CL = Clearance) - Rate of elimination is proportional to _______ ______ in 1st order elimination.
- drug concentration
- In the case of EtOH, which is elimated by _____ order elimination, a constant amount of drug is eliminated per unit time.
- zero
- Phase ____ (I or II) reactions yield slightly polar metabolites that are often _____ (active or inactive)
- I, active
- Phase ____ (I or II) reactions yield very polar metabolites that are often _____ (active or inactive) and are excreted by the _______.
- II, inactive, kidney
- Phase II reactions are often of this type.
- conjugation
- Cytochrome P-450 is involved in _____ phase (I or II) reactions.
- I
- A drug patent lasts for _____ years after filing for application.
- 20
- How many phases are there in drug development?
- 4
- Drugs are first tested in patients in phase _____ of clinical testing, pharmacokinetic safety is determined in phase ______ of clinical testing, double blind tests are done in phase ____ and post-market surveillance is done in phase _____.
- 2,1,3,4
-
In a dose response curve, a competitive antagonist shifts the curve _____
a non-competitive antagonist shifts the curve ______. -
right
down - What pharmacologic relationship would determine the existence of spare receptors?
- EC50 is lower then Kd (EC50 is more to the left)
- What does it mean if EC50 and Kd are equal?
- The system does not have spare receptors
- A partial agonist acts on the same receptor system as a full agonist? T/F
- TRUE
- What's the main difference between a partial agonist and a full agonist?
- A partial agonist has a lower maximal efficacy.
- Is a partial agonist less potent than a full agonist?
- Not necessarily. It can be less, more or equally potent as a full agonist.
- Equation for Half Life
- T 1/2 = (0.7 x Vd)/CL
-
Percent of concentration in the following number of half lives:
1
2
3
3.3 -
1 = 50%
2 = 75%
3 = 87.5%
3.3 = 90% - How do the Loading and Maintenance doses change in a patient w/ Renal or Hepatic dysfunction?
-
Loading - unchanged
Maintenance - Decreased - Equation for Theraputic Index
- TI = Toxic dose/Effective dose
-
Phase in clinical drug testing:
safety, pharmacokinetics - 1
-
Phase in clinical drug testing:
Protocol, dose level, work on patients - 2
-
Phase in clinical drug testing:
double blind study, efficacy, adverse effects - 3
- (3) drugs that use Zero-order elimination
-
Alcohol,
Aspirin,
Phenytoin -
What phase of a reaction uses cytP-450?
What is the purpose of this phase? -
Phase I
converts lipophilic to polar - What is the main focus of Phase II reactions?
- Conjugation
-
When pH < pKa, what is more common?
(2)
which can pass through the membrane? -
HA and BH+
HA passes thru the membrane (uncharged) -
Definition:
Amount of the drug required for a given response - Potency
-
what is the first NT to everything?
the first receptor? -
NT: ACh
Receptor: Nicotinic - what system does not have a synapse from the spinal cord to the tissue?
-
Somatic NS
(skeletal muscle)
ACh to Nicotinic receptor -
what is the only sympathetic ACh?
what is the receptor? -
Sweat gland
receptor: Muscarinic - what is the receptor for the Parasympathetic system at the tissue?
- Muscarinic
-
what are the Adverse Effects of Acetylcholine?
which is the only Nicotinic receptor response? -
DUMBBELSS:
Diarrhea, Urination,
Miosis,
Bradycardia, Bronchoconstriction,
Excite skeletal muscle (N),
Lacrimation,
Sweat, Salivation -
what receptors use Gq as their second messenger?
(5) -
HAVe 1 M&M:
H1
Alpha1
V1
M1
M3 - what G-protein uses Phospholipase C?
- Gq
-
what receptors use Gi as their second messenger?
action? -
MAD 2s:
M2
Alpha2
D2
inhibits Adenylyl Cyclase - what receptor increases gastric acid secretion?
- H2
- Inhibits choline re-entering the presynaptic terminal
- Hemicholinium
- Inhibits ACh into vesicles
- Vesamicol
- Inhibits NE into vesicles
- Reserpine
- Inhibits release of ACh into synaptic membrane
- Botulinum
- Inhibits release of NE into synaptic membrane
- Guanethidine
- Promotes release of NE into synaptic membrane
- Amphetamines
-
Inhibits reuptake of NE into presynaptic nerve
(2) -
Cocaine
TCA - what receptor does NE act on in the presynaptic neuron as neg feedback to inhibit its release?
- alpha-2
- (3) Cholinomimetrics and use of each
-
Bethanechol - post-OP activates GI/GU
Carbachol - Glaucoma
Pilocarpine - Glaucoma -
Anticholinesterase used for post-OP activation of GI/GU, myasthinia gravis
what is it an antidote for? -
Neostigmine
antidote: Curarae (NMJ block) -
Anticholinesterase used for glaucoma and crosses BBB
what is it an Antidote for? -
Physostigmine
antidote: Atropine overdose - (3) ACh receptor blockers
-
Atropine,
Scopalamine,
Ipratropium - ACh receptor blocker used for Motion Sickness
-
Scopolamine
(DOC) - ACh receptor blocker used for Asthma/COPD
- Ipratropium
- what drug slows the HR at 0.5mg and increases it at >1.0mg?
-
Atropine
(muscarinic antagonist) - what are the AE of Atropine?
-
Opposite of DUMBBELSS:
Hot as hare,
Dry as bone,
Red as beet,
Blind as Bat,
Mad as hatter - Insecticide antidote
- Atropine
-
Nicotinic ACh receptor antagonist
use? -
Hexamethonium
use:
prevents reflex bradycardia caused by NE - drug used for intubation for its rapid onset and quick duration in causing flaccid paralysis
- Succinylcholide
- which NMJ (nicotinic) blocker also releases histamine?
- Tubocurarine
-
Epinepherine effects on:
1. BP
2. HR
3. TPR -
Epinepherine
BP: Inc Systolic, Dec Diastolic
HR: Inc (tachycardia)
TPR: Dec -
NE effects on:
1. BP
2. HR
3. TPR -
NE
BP: BIG INC in systolic and diastolic
HR: DECREASES
TPR: BIG INCREASE -
Isoproterenol effects on:
1. BP
2. HR
3. TPR -
Isproterenol
BP: Decrease in systolic and diastolic
HR: BIG INCREASE
TPR: BIG DECREASE - DOC for Shock to increase renal perfusion and for CHF to increase CO
- Dopamine
- DOC for CHF to increase CO w/o increasing oxygen demand
- Dobutamine
- Alpha agonist that is used for HTN w/ renal Dz
- Clonidine
- what occurs if atropine is given before NE?
- Heart rate increases instead of decreases
- a1-blocker for urinary retention in BPH and HTN
- Prazosin
- a2-blocker for depression
- Mirtazapine
- what occurs w/ BP if a-blocker is given before Isoproterenol?
- No change!
- what occurs w/ BP if a-blocker is given before Epinepherine?
- Reverses the vasoconstriction effect of Epi and Decreases BP
- which beta-blockers are beta1 selective?
-
if they start w/ A-M in alphabet
(except Labetalol - partial agonist) - what glaucoma drug should not be used in closed-angle glaucoma?
- Epinepherine
-
Antidote/Tx for:
Salicylates - Alkalinize urine
-
Antidote/Tx for:
Anticholinesterases;
Organophosphates
(2) -
Atropine,
Pralidoxime -
Antidote/Tx for:
Antimuscarinic;
Anticholinergic agents - Physostigmine
-
Antidote/Tx for:
beta-blockers - Glucagon
-
Antidote/Tx for:
Digitalis
(4) -
Stop Dig,
normalize K,
Lidocaine,
Magnesium -
Antidote/Tx for:
Iron - Deferoxamine
-
Antidote/Tx for:
Lead
(3) -
CaEDTA,
Dimercaprol,
Succimer (kids) -
Antidote/Tx for:
Arsenic, gold, mercury
(2) -
Dimercaprol,
Succimer (kids) -
Antidote/Tx for:
Copper - Penicillamine
-
Antidote/Tx for:
Cyanide
(3) -
Nitrite,
Hydrocobalamin,
Thiosulfate -
Antidote/Tx for:
Methemoglobin - Methylene Blue
-
Antidote/Tx for:
Carbon Monoxide -
100% O2
(or hyperbaric O2) -
Antidote/Tx for:
Methanol,
Ethylene glycol (antifreeze)
(2) -
Ethanol,
Fomepizole -
Antidote/Tx for:
Opioids
(2) -
Naloxone,
Naltrexone -
Antidote/Tx for:
Benzodiazepines - Flumazenil
-
Antidote/Tx for:
TCAs - NaHCO3
-
Antidote/Tx for:
Heparin - Protamine
-
Antidote/Tx for:
Warfarin
(2) -
Vitamin K,
FFP -
Antidote/Tx for:
tPA, Streptokinase - Aminocaproic acid
-
Urine pH and drug elimination for:
Weak acids - alkalinize urine w/ Bicarb
-
Urine pH and drug elimination for:
Weak bases - Acidify urine w/ NH4Cl
- What is the reversible cholinesterase inhibitor indicated for the Tx of Alzheimer's Dz?
- Tacrine
- what is the skeletal muscle relaxant that acts directly on the contractile mechanism of the muscle fiber?
- Dantrolene
- which Glaucoma agent acts by decreaseing production of aqueous humor?
- Timolol
- why is Epi mixed w/ anesthetics?
- to retard the systemic absorption
- which muscles are most affected by tubocurarine?
- fine movement muscles (head, neck, face)
- what is the alpha receptor-assoc eye muscle?
- Radial muscle
- what agent for bronchial asthma causes tremor?
-
Salmeterol
(b-agonist) -
what ANS drug class masks hypoglycemia in treated diabetics?
how? -
b-blockers
blocks catecholamines, which stimulate Glyconeogenesis - (2) MAO inhibitors that are used for depression
-
Tranylclpromine,
Phenelzine sulfate - DOC for thyroid storm
- Propranolol
-
Definition:
two drugs act on the same tissue via independent receptors resulting in effects in the opposite direction - Physiologic antagonist
-
Definition:
when two drugs combine and the activity of one or both drugs is blocked - Chemical antagonist
-
equation for the Elimination constant
(2) - Ke = 0.7/half-life = CL/Vd
- when calculating an IV dosage, what needs to be remembered?
- multiply drug (mg/kg) by weight (kg)
- (2) equations for Extraction ratio
- ER = (Ci-Co)/Ci = CL/Q
-
Which is not absorbed well in the stomach:
Aspirin (pKa = 3) or Propranolol (pka = 9.4)? - Propranolol
- the AE of convulsions are MC w/ what drug?
- Strychnine
- what drug can cause Hypocalemic Tetany?
- Edetate Disodium (Na-EDTA)
- what mineral toxicity can decrease Amylase secretion?
- Zinc
- AE of drug is Congenital goiter, Hypothyroidism
- Methimazole
- AE of drug is Agenesis of fetal kidneys
- Chlorambucil