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General Principles of Pharmacology- Part 2
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1.The official “package insert” for prescription drugs identifies (among many other things) the specific use(s) or indication(s) for the drug approved by the It i s also l ikely to note one or several more so-called “off-label” uses: uses that have not been sanctioned officially by the FDA, but for which there i s reasonable evidence that the drug i s both safe and effective. For which other uses can you, as a licensed physician, administer or prescribe these FDA-approved drugs?
- Anything you wish, provided no specific laws (eg, controlled-substance laws) prohibit i t
- None—only FDA approved and written off-label uses
- Only approved and off-label uses for older drugs in the same chemical class (eg, another thiazide diuretic, benzodiazepine, etc)
- Only approved and off-label uses of older drugs used for the same purpose (eg, another antihypertensive, antidepressant, or cancer chemotherapeutic agent, etc)
- Only uses for which there i s some evidence of drug efficacy and safety in the experimental l i terature
2. When new drugs undergo preclinical testing, one of many things to know i s whether i t’s largely confined to the vascular compartment or distributed more widely, perhaps to specific ti ssues such as the l ipid-rich This i s , of course, ultimately cl inically important i f the drug eventually gets FDA approval. One way to get a handle on that i s to calculate the apparent volume of distribution (Vd).
The table and graph below show some data concerning a new amino-glycoside antibiotic. We give an IV dose (5 mg/kg) of the drug to a 70-kg 21- year-old volunteer, who i s healthy and taking no other drugs. After allowing time for redistribution and equilibration of the drug in various body compartments, we measure plasma concentrations at various times.
Which value comes closest to the apparent Vd for this drug? (By all means, feel free to use your favorite calculator.)
- 0.62 L
- 19 L
- 50 L
- 110 L
- 350 L
3. You are reviewing the data from several meta-analyses that addressed the most common causes of adverse or otherwise excessive effects of prescription drugs in young adults and in the elderly (>60 years of age). Interactions between multiple drugs were not Which variable would you find to be decreased, and be the most common general cause of these problems, in the elders?
- Body fat content
- Lean body mass
- Liver function
- Renal function/clearance
- Plasma albumin levels
4. Some texts state that the ability of one drug (sometimes called the “object drug”) to displace molecules of another drug (the “target drug”) from plasma protein binding s i tes, thereby raising the concentration and activity of free target drug in the blood, i s not cl inically The claimed reason? “Drug molecules that are displaced are rapidly eliminated and the equilibrium between bound and free drug i s rapidly reestablished.” This interpretation may be correct for some drugs, but not for others.
Considering only the pharmacokinetics or other relevant properties of the target drug, upon which drug-related variable does the speed of elimination and reestablishment of the bound versus free equilibrium—indeed, whether the interaction i s apt to be cl inically relevant—depend the most?
- Overall elimination t1/2
- pK (acid or base)
- Renal clearance
- Whether the drug i s metabolized, or excreted without prior metabolism
5. Upon evaluating the effects of certain sympathomimetic drugs in a variety of in vi tro and in vivo models, you find that the responses exhibit the phenomenon of tachyphylaxis. What does the term tachyphylaxis mean?
- An increase in the rate of the response, for example, an increase of the rate of muscle contraction
- Immediate hypersensitivity reactions (ie, anaphylaxis)
- Prompt conformational changes of the receptor such that agonists, but not antagonists, are able to bind and cause a response
- Quick and progressive ri ses in the intensity of drug response, with repeated administration, even when the doses are unchanged
- Rapid development of tolerance to the drug’s effects
6. A postoperative patient will require prolonged We choose a drug that has the following pharmacokinetic properties: Half-life: 12 hours
Clearance: 0.08 L/min Volume of distribution: 60 L
The patient has an indwelling venous catheter with a s low drip of 0.9% Na Cl , and we will use this to administer intermittent injections of the drug every 4 hours. The target blood level of the drug, following each injection, i s 8 mcg/mL.
With this plan in mind, and using no loading dose of the drug, which one of the following comes closest to the dose that should be administered every 4 hours?
- 0.960 mg (or 1 mg)
- 6.4 mg (or 6 mg)
- 25.6 mg (or 25 mg)
- 150 mg
- 550 mg
7. A patient i s experiencing severe postoperative pain, and we need to give a loading dose of an analgesic drug for prompt relief of The drug we choose has the same pharmacokinetic properties as the one described in Question 24:
Half-life: 12 hours
Clearance: 0.08 L/min Volume of distribution: 60 L
Our target plasma concentration for the drug i s 8 mcg/mL. What number comes closest to the correct loading dose?.
- 0.48 mg (rounded to 0.5 mg)
- 150 mg
- 320 mg
- 480 mg
- 640 mg
8. We administer a highly l ipid-soluble drug and monitor i ts elimination in vivo and in vi All the data indicate that i t i s transformed to a variety of more polar and oxidized metabolites by a group of heme proteins that activate molecular oxygen to a form that i s capable of interacting with organic substrates such as our test drug. What enzyme or enzyme system i s most l ikely involved in the initial metabolism of this drug?
- Cytochrome P450s (CYP system, mixed-function oxidases)
- Monoamine oxidase (MAO)
- Nicotinamide adenine dinucleotide phosphate (NADPH)
9. We measure the heart rate of a healthy subject under the conditions noted below, allowing ample time for return to baseline conditions and full elimination of drugs between each step:
- At rest
- During treadmill exercise sufficient to activate the sympathetic nervous system at a time when maximum heart rate i s reached
- After administration of acebutolol, a drug with affinity for β-adrenergic receptors
- After giving acebutolol, followed by exercise at the same level used in condition 2
Acebutolol given at rest causes a s l ight but consistent increase in heart rate. Give a bigger dose at rest and heart rate ri ses a bit more. When the patient exercises after receiving a low-dose acebutolol, heart rate ri ses s ignificantly less than i t did in the absence of acebutolol.
With exercise after the higher dose of acebutolol, the tachycardia i s blunted even more.
The figure below summarizes the main findings.
Which statement best summarizes the actions of acebutolol?
- Has higher affinity for adrenergic receptors than the endogenous agonists, epinephrine, and norepinephrine
- Is a partial agonist for β-adrenergic receptors
- Is activating spare receptors on myocardial cells
- Is an i rreversible or noncompetitive β-blocker
- Is changing conformation of the adrenergic receptors
10. We are planning to infuse a drug intravenously at a constant amount per unit time (rate). It has a first-order elimination rate constant (kel) of 35/h. No loading dose will be given. Approximately how long will i t take for blood levels to reach steady state after the infusion begins?
- 0.7 hour
- 1.2 hours
- 3.5 hours
- 9 hours
- 24 hours
11. A patient who i s supposed to be taking a drug once a day gets confused and for a couple of days takes excessive daily doses, leading to The drug has a mean plasma half-life of 40 hours.
Right now the patient’s plasma concentration of the drug i s 6 mcg/mL. Although what to do next will depend on actual blood tests for drug levels, the usual plan in this case i s to have the patient skip one or several daily doses of the drug until blood levels fi rst enter the therapeutic and nontoxic range, which in this case i s 0.8 mcg/mL. Assume the drug i s eliminated by fi rst-order kinetics. How many daily doses should be withheld?
12. We want to calculate the apparent volume of distribution (Vd) for a hypothetical drug (drug A) that has a half-life of 4 All (100%) of an absorbed dose of this drug undergoes Phase I oxidation, followed by conjugation (Phase II reaction) and then renal excretion.
We rapidly inject a known dose, and 30 minutes later begin taking serial blood samples (30 min apart) and quantifying drug concentration in each sample. What one other piece of information must be measured or otherwise determined to calculate Vd in the easiest way?
- Area under the drug concentration-time curve (AUC)
- Bioavailability (F)
- Clearance (Cl)
- El imination rate constant (kel)
- Maximum blood concentration after the bolus injection (C0)
13. A patient with a bacterial infection requires intravenous antibiotic The chosen drug has a clearance (Cl) of 70 mL/min. The apparent volume of distribution (Vd) i s 50 L. The plan i s to administer the drug intravenously every 6 hours and achieve a 4 mg/L steady-state blood level of the drug. No loading dose strategy i s to be used. What maintenance dose i s needed to achieve this?
- 14 mg
- 24 mg
- 100 mg
- 300 mg.
- 1200 mg
14. A pharmacologically inert but easily measured substance, X, i s eliminated in a manner that follows l inear kinetics (fi rst-order plot of log drug concentration vs time during elimination i s a straight l ine). The plasma half-life i s 30 Bolus IV doses well in excess of 100 mg must be given in order to saturate the enzymes responsible for metabolizing the drug, which will then lead to zero-order elimination kinetics.
We infuse a solution of X intravenously. The concentration of the solution i s 2 mg/mL; the infusion rate i s 1 mL/min and i s kept constant at that.
We continue the infusion for 24 hours.
After allowing ample time for the drug to be eliminated completely, we repeat the administration. This time the concentration of the solution of X i s 4 mg/mL, and we infuse i t at a rate of 2 mL/min.
Which other variable will also be changed as a result of the stated changes to the infusion protocol?
- El imination rate constant
- Plasma concentration when CSS i s reached
- Time to reach steady-state
- concentration (CSS) e.
- Total body clearance
- Volume of distribution
15. A new drug, drug A, undergoes a series of Phase I metabolic reactions before i ts metabolites ultimately are Which statement best describes the characteristics of drug A, or the role of Phase I reactions in i ts metabolism or actions?
- Complete metabolism of drug A by Phase I reactions will yield products that are less l ikely to undergo renal tubular reabsorption
- Drug A i s a very polar substance
- Drug A will be biologically inactive until i t i s metabolized
- Phase I metabolism of drug A involves conjugation, as with glucuronic acid or sulfate
- Phase I metabolism of drug A will increase i ts intracellular access and actions
16. Dopamine, epinephrine (or norepinephrine), and histamine are important neurotransmitter When these l igands interact with their cellular receptors, how do they mainly elicit their responses?
- Activating adenylyl cyclase, leading to increased intracellular cAMP levels
- Activating phospholipase C
- Inducing or inhibiting synthesis of l igand-specific intracellular proteins
- Opening or closing l igand-gated ion channels
- Regulating intracellular second messengers through G protein-coupled receptors
17. You have just evaluated and started treatment on a 40-year-old woman in whom you have diagnosed malignant hypertension, based on her history, her cl inical presentation, and the blood pressure changes you measured over the relatively short time you’ve been at the You now go to the family, in the waiting room, and explain your diagnosis. You explain that hypertension means high blood pressure. But when they heard the word malignant one of the family members says “Oh, her blood pressure i s high because she has cancer?” How should you best explain the term to the family?
- Blood pressure i s ri s ing very quickly and dangerously
- Cancer i s present, but i t i s not the cause of the high blood pressure
- Her high blood pressure i s , indeed, caused by a cancer (“malignancy”—in this case probably an adrenal cortical tumor—a pheochromocytoma)
- Her high blood pressure did not fall in response to a blood pressure medication that i s effective for most patients
- The hypertension i s l ikely to prove fatal (eg, from a ruptured aneurysm in the brain or elsewhere)
18. The Food and Drug Administration has broad regulatory authority over prescription drugs, over-the-counter (OTC) drugs, and nutritional supplements (herbals and other so-called nutriceuticals). This authority includes approval, marketing (advertising), and withdrawal of drugs from the Which statement summarizes an element of FDA rules or guidelines?
- Drugs approved for sale OTC fi rst received FDA approval for sale and marketing “by prescription only”
- If a pharmaceutical manufacturer provides data sufficient to obtain FDA approval for sale by prescription, the manufacturer i s then allowed to sell the drug over-the-counter (OTC)
- If the FDA approves a prescription drug for sale (prescribing), the physician can prescribe the drug only for the FDA-approved indication (use)
- Nutritional supplements can be marketed without providing proof of efficacy or safety to the FDA
- Phase III testing of prescription drugs that have been approved by the FDA gives complete information about adverse responses and pertinent drug-drug interactions