BIO200H5 Lecture Notes - Lecture 8: Fluid Compartments, Half-Life, Bioavailability

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9 Nov 2018

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I am going to inject the drug: the beaker with blood is connected to an extravascular compartment (say its water, there is no output. I have a beaker that has an output = input, blood is still connected to extravascular volume. Inject the drug, rise of concentration: because there is an output and a balance of the 2 compartments (which represents the distribution), there will be a fast rate of decay. If half-life of a drug is very long, you only need probably 1 dose a day, or 1 dose a week: half-life will not only determine the maximum concentration, but also the rate of elimination. If half-life of drug is really long, the elimination will be very long, so the drug will stay longer in the body. Some diseases will affect the volume of distribution and clearance: patients will chronic renal failure, you have to increase the dosing interval.

Related Questions

Need help with biology questions:

1. To increase the excretion of an acidic drug, what would you do to the urine?

	A.	Make it more basic
	B.	None of the above
	C.	Make it neutral
	D.	Make it more acidic

2. G-Protein coupled receptors directly act on which of the following secondary messenger molecules:

	A.	cAMP
	B.	ATP
	C.	ADP
	D.	GTP
	E.	None of the above or more than one of the above

3. Drug A and Drug B both produce the same level of biological/physiological response. Drug A produces this effect with 100 mg/kg dose. Drug B produces this effect with 50 mg/kg dose. Which of the following is true?:

	A.	Drug B is more efficacious than Drug A. Both drugs are equally potent.
	B.	Drug A is more efficacious than Drug B. Both drugs are equally potent.
	C.	Drug A and B are equally efficacious. Drug A is more potent than Drug B.
	D.	Drug A and B are equally efficacious. Drug B is more potent than Drug A.

4. The stomach has a ______ pH, whereas the small intestines have a _______ pH. The colon has an approximately ___________ pH.

	A.	High; low; neutral
	B.	Low; high; neutral
	C.	Low; neutral; neutral
	D.	None of the above

5. Which receptor is most likely to reduce norepinephrine levels when activated?

	A.	alpha 2 adrenergic
	B.	alpha 1 adrenergic
	C.	dopamine D1 receptors

6. Which of the following statements are FALSE?

	A.	If the Vd of a drug is between 60 and 80 L the drug has likely distributed to the total body water of a 200 kg man.
	B.	In the enterohepatic system the activity of bacteria to remove conjugates from a drug in the gut will decrease the clearance of the drug.
	C.	Lipid drugs are more likely to be reabsorbed by the kidney from the urine.
	D.	A weak basic drug (pKa = 6) will be mostly ionized in urine of a pH= 3 and only the non- ionized drug will be eliminated.
	E.	The major conjugate in Phase 2 metabolism is glucuronide.

7. Isoproterenol (Î²-agonist) is a vasodilator that increases HR. What happens to systolic and diastolic pressures upon IV administration of isoproterenol?

	A.	â systolic; â diastolic
	B.	â systolic; â diastolic
	C.	â systolic; â diastolic
	D.	â systolic; â diastolic
	E.	None of the above

8. If you want to increase the blood concentration of a drug A, you can perform which of the following procedures:

	A.	Inhibit Drug A metabolism with Drug B
	B.	Enhance Drug A reabsorption from renal proximal tubule by changing ionization of Drug A with Drug B
	C.	Allow competition of Drug B with Drug A for active renal secretion processes
	D.	Increase the binding of Drug A to serum albumin
	E.	All of the above

9. Which of the following describes Phase I metabolism?

	A.	Inactive products are always produced in this phase.
	B.	Large molecules such as glucuronic acid are conjugated to drugs in this phase.
	C.	This phase may produce active metabolites from prodrugs.
	D.	This phase only occurs in the liver.

10. Which of the following is NOT an enzyme involved in the biosynthesis of biogenic amines?

	A.	Phenylethanolamine N-methyl Transferase
	B.	Dopamine Î²-hydroxylase
	C.	Tyrosine dehydroxylase
	D.	DOPA decarboxylase
	E.	All of the above

11. Why would an antibiotic at the same concentration be more active against bacteria in water than in serum or plasma? (Activity is measured in a test tube)

	A.	activity of the antibiotic is increased in water.
	B.	due to drug-protein interaction in serum
	C.	the antibiotic is more stable in water
	D.	all of the above
	E.	none of the above

12. Ion channels are targets for drugs. Which drug class targets Na+ channels?

	A.	Benzodiazepines
	B.	Beta blockers
	C.	Local anesthetics
	D.	Antihypertensive drugs (cardiac and smooth muscle)
	E.	Glibenclimide (diabetic drug)

13. _________________ not metabolized by catechol-O-methyltransferase (COMT).

	A.	Dopamine
	B.	Epinephrine
	C.	Phenylephrine
	D.	Norepinephrine
	E.	All of the above are metabolized by COMT.

1) The neurotransmitters acetylcholine and norepinephrine are digested by enzymes that are located at the axon synapse or within the axon terminal of the neurons.

a)What are the names of these different types of enzymes?

b)Where are they located and what is the result of their enzymatic activity?

2) Explain how the Investigational New Drug process works as well as the four different phases of clinical trials. Why are some drugs still taken off the market after approval by the FDA?

3) A single IV injection of 100 mg drug with a half-life of 4 hours is administered to a young adult.

a) Plot drug concentration versus time on a graph making certain to clearly label.

b) How long will it take to eliminate > 95% of the drug?

c) If the volume of distribution is 4L, what is the clearance of the drug?

4) Many drugs are metabolized in the liver through the microsomal metabolizing system.

a) What specific enzymes are involved in this metabolism?

b) What are the main functions of these enzymes?

c) What are some factors that can contribute to individual drug metabolism variation? Explain.

5) Think of an emergency situation requiring immediate and intense physical exertion.

a) List as many body organs as you can and predict the desired level of activity [increased or decreased].

b) Which neurotransmitter would produce these effects and through what receptors?

6) It is interesting that a drug can produce a therapeutic effect and an undesired side effect in one situation, and that the same drug side effect may be considered a therapeutic effect in another situation. Explain this phenomenon using the drug promethazine as an example.

7) A patient brought into the emergency room is experiencing severe hypotension. Blood pressure reads 90/50.

a) What class of drugs is indicated for treatment and why?

b) What precautions should be observed when these drugs are administered?

c) What would be the first indication that too much drug has been administered?

8) Only certain drugs are capable of crossing the blood brain barrier.

a) How is the blood brain barrier different than barriers found in other areas of the body? Be specific.

b) What properties of drugs will make it more likely to cross the blood brain barrier? Explain your answers.

9) A 32-year-old, presents to the Emergency Department by ambulance with vomiting, confusion, salivation, and respiratory distress. The patient states that he was feeling fine until today when I started getting ill. He then vomits. During a physical exam you record the following information: Heart rate 45; Blood pressure 90/60; Respiratory rate 25; Temperature 36.6C; Pupils constricted. During your exam, 4 more ambulances arrive with patients with similar symptoms. You find out they were all riding in the same care on the Red Line when they began feeling ill.

a) What do you feel is happening and why?

b) Would you expect their symptoms to improve over time? Why or why not?

c) What drug would you prescribe to treat these patients and why?

10) Betty has diabetes and asthma. She also has developed high blood pressure, for which doctor just prescribed propranolol. One of your duties as a physicianâs assistant is to make sure patients are not prescribed drugs that are contraindicated because of other health problems.

a) What should you tell the doctor about Bettyâs prescription for propranolol and why?

b) Is there a more appropriate drug for Betty? Explain you answer.

Question 5. Dr. Campbell used an elliptical trainer for 40 minutes at the gym. Although the workload remained constant, Dr. Campbellâs heart-rate rose to 150 beats per minute during the first 5 minutes, stayed at that level for the next 25 minutes and then started to rise. It was 180 beats per minute at the end of the exercise period.

What was the time interval between QRS complexes when Dr. Campbellâs heart rate was 180 beats per minute?

a. 3.3 ms

b. 33 ms

c. 333 ms

d. 3333 ms

Question 6. In the question 5 above, Dr. Campbellâs heart rate is most likely to have risen during the last 10 minutes of exercise because his:

a. lungs were becoming congested

b. atrial cells were fatigued

c. extracellular Ca2+ concentration had increased

d. hematocrit increased due to sweating

Question 7. A Physiology student is sitting still in a cold igloo. After 30 minutes, she stands up, walks slowly around the igloo, and suddenly starts to shiver.

The student preserved their core temperature while they were sitting by:

a. depressing their Frank-Starling mechanism

b. decreasing the extracellular Ca2+ concentration

c. relaxing smooth muscles in their peripheral circulation

d. increasing the resistance of arterioles in their arms and legs

Question 8. In the question 7 above, the student started to shiver soon after walking because:

a. their atria started to fibrillate

b. their ventricles started to fibrillate

c. blood moved to the periphery, became cold, and chilled the core when it returned to the chest

d. the ATP concentration in their skeletal muscles had dropped to zero

Please use the following scenario for answering the questions 9 and 10.

A newly discovered drug binds to myosin molecules in cardiac muscle (and nowhere else) and increases the probability that myosin molecules in ventricular cells will bind to actin filaments when the intracellular Ca2+ concentration rises. The drug is being tested as a potential therapy for patients with heart failure.

Question 9. This drug might help people who have low cardiac output by:

a. increasing peripheral resistance

b. increasing the force developed by ventricular cells

c. increasing the isovolumic contraction time

d. increasing heart rate

Question 10. The increased binding of cardiac myosin molecules to actin might prevent the drug from being a useful treatment by:

a. slowing ventricular relaxation

b. decreasing the duration of systole

c. decreasing resistance of capillaries

d. slowing heart rate

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BIO200H5 Lecture Notes - Lecture 8: Fluid Compartments, Half-Life, Bioavailability

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