Chapter 1 Introduction to Pharmacology Answer Key

You can review additional information regarding these answers in the corresponding section in which the Critical Thinking activities appear.

1.3 Pharmacokinetics – absorption

1. The rectal route may be a good option for clients who have other health issues such as nausea, vomiting, confusion, sedation, or NPO. PR has less of an impact on the bioavailability of the drug and has a faster onset of action, shorter duration and a shorter peak effect.

Oral route is more convenient and easy to administer, and less embarrassing for some clients. It is a good option if the client can swallow easily. But, oral route is subject to first-pass effect which will have a reduced bioavailability and a slower onset of action.

1. The IV route bypasses the first-pass effect which results in greater drug bioavailability. In addition, IV results in much quicker onset of action, shorter duration, and shorter peak effect. But, if an IV is not yet started, then this may delay giving the med and an IV can be painful to insert.   IM route has a slower onset of action and a longer duration of action. It is a good option to achieve a more sustained pain control due to the slower absorption.

1.4 Pharmacokinetics – Distribution

1. Low serum albumin means there are fewer albumin molecules so there is less receptor sites on the albumin molecules for a drug to attach themselves. This leaves more free drug in the bloodstream that can diffuse to the tissues and target site, leading to a greater drug effect.
2. Since it will be more bound to proteins in the blood, it will have a slower onset of action. If it is also water soluble, it will have less volume of distribution and more of the drug will stay in the blood and have a shorter duration of action.  If the drug was lipid soluble and poorly bound to protein, it will more easily be taken up by the tissues and distributed throughout the body.

1.5 Pharmacokinetics – Metabolism

The biotransformations that take place in the liver are performed by the liver enzymes. Therefore, if the liver is damaged, metabolism and excretion are impacted, resulting in the need for lower dosages to avoid toxicity.  Clients with cirrhosis requires strict medication management due to the liver’s impaired ability to metabolize drugs, which increases the risk of toxicity, adverse drug reactions, and exacerbation of complications. Nurses should monitor blood work such as liver function tests (ALT, AST, Bilirubin), renal function and serum albumin levels. Physical assessment for all liver failure clients should include mental health status, fluid status, nutritional status and blood pressure.

1.6 Pharmacokinetics – Excretion

Kidney function is important because drugs and metabolites in the bloodstream are often filtered by the kidney.  In the kidney tubules, a portion of the drug undergoes reabsorption back into the bloodstream, and the remainder is excreted in the urine.

1.7 Pharmacodynamics

Potency refers to the ability of a drug to produce its effect at low doses. It does not mean it will cause more adverse or toxic effects. A high potency drug will produce a strong effect at low doses. For example, fentanyl is considered a potent drug.

1.9 Monitoring for Effects

Learning Activity 1

1. Nursing considerations when administering pain medication include efficacy, dose-response based on the dosage selected, onset, peak, duration, and half-life of the drug. The patient has physical therapy scheduled at 0900, so the nurse should administer acetaminophen now to relieve the pain and evaluate the effectiveness in 60 minutes. The nurse should also plan on reassessing the patient’s pain and potentially administering a second dose of acetaminophen just prior to the physical therapy appointment because the half-life of acetaminophen is two to three hours. Additionally, acetaminophen has a 24-hour dose restriction, so the nurse should calculate how many total milligrams the patient has received over the past 24 hours prior to administering the medication.
2. Insulin is a high-alert medication due to severe side effects that can occur if administered incorrectly. The nurse should check the patient’s blood sugar reading and consider withholding the medication if the patient continues to refuse food over the next few hours to avoid causing hypoglycemia. The provider may also need to be notified of the patient’s change in condition and a change in the medication order may be required.

Learning Activity 2

Mr. Parker’s gentamycin level is much higher than the therapeutic level of 5 to 10 mcg/mL.  The nurse should inform the prescriber and anticipate the next dose being held, and subsequent dosages decreased. The med may also be substituted with a different med. The client will have repeat peak and trough levels done the following day to ensure they are within the therapeutic window.  Gentamycin levels that are in the toxic range can cause nephrotoxicity and ototoxicity.  Loss of hearing can be irreversible. The client will likely also have renal function blood work done to ensure there are no issues.

1.10 Critical Thinking and Decision-Making Activities

1. The nurse should select the rectal route due to the patient’s difficulty swallowing to reduce the risk of aspiration.
2. The initial dose is less than the standard recommended dose based on Mr. Johnson’s age and the likelihood that his kidney functioning is decreased.  Decreased kidney function affects the metabolism and excretion of gentamycin and could result in toxicities if the dose is too high.
3. Sara should wait to administer the medication until the patient’s trough level is drawn. The trough level is required for the provider and the pharmacist to determine if the medication is within the range of the therapeutic window and to avoid the risk of toxicity to the patient.
4. Sam should evaluate the patient’s vital signs, specifically the apical pulse and blood pressure, to be sure they are within the normal range for this patient and the parameters prescribed by the provider. Atenolol has negative inotropic, chronotropic, and dromotropic effects.  The negative inotropic effect weakens the contraction of the heart and lowers blood pressure. The negative chronotropic effect decreases the heart rate, and a negative dromotropic effect slows the conduction of the electrical charge in the heart. Understanding the effects of this Beta-1 antagonist medication allows Sam to anticipate the expected actions of the medication and the patient’s response.
5. Amiodarone is metabolized by the enzymes in the intestines to its active form. Grapefruit juice contains compounds that slow down this process and affect the levels of this medication in the blood. The nurse should educate Julia about this interaction and encourage other beverage choices in the future that do not cause this interaction.
6. The nurse anticipates that oxycodone/acetaminophen will peak in approximately 1 hour. The patient will likely require another dose of medication for acute, severe pain that accompanies a knee replacement in approximately 4 hours.