Basics of Pharmacology Part II

Summary

This lecture covers key aspects of pharmacology, focusing on drug actions, effects, and side effects. It explains the concepts of drug half-life, therapeutic levels, and the importance of monitoring drug levels to avoid toxicity. The lecture also highlights potential adverse effects on various body systems, including the nervous, liver, gastrointestinal, urinary, and hematology systems. Emphasis is placed on the role of healthcare professionals in understanding medication administration, monitoring patient responses, and ensuring effective treatment with minimal side effects.

Takeaways

• 💊 Drugs are eliminated from the body through metabolism and excretion, with half-life being the time required to eliminate 50% of the drug.
• ⏳ Half-life impacts dosing frequency; longer half-lives mean less frequent dosing, which is important for geriatric patients.
• 📈 Drugs have an onset, peak, and duration; understanding these helps manage therapeutic levels and side effects.
• 🩺 Therapeutic levels are essential for drug effectiveness; levels too low render the drug ineffective, while too high can cause toxicity.
• 👂 Certain drugs can cause ototoxicity (ear damage) and nephrotoxicity (kidney damage), highlighting the importance of monitoring.
• 📉 Side effects of medications can range from mild (nausea) to severe (adverse reactions like anaphylaxis), with some side effects being system-specific.
• ⚠️ Allergic reactions, including anaphylaxis, are medical emergencies; patients should wear medical alert bracelets.
• 🧠 Nervous system side effects include confusion, depression, and delirium, while the liver and GI system are also susceptible to drug damage.
• 🔬 Monitoring blood levels and patient symptoms is crucial for safe and effective medication administration.
• 👩‍⚕️ Healthcare professionals must understand drug actions, side effects, and proper administration to advocate effectively for patients.

Q & A

What is the definition of half-life in pharmacology?

Half-life in pharmacology refers to the time required for 50% of a drug to be eliminated from the body.

Why is half-life important when considering medication for geriatric patients?

Half-life is important for geriatric patients because medications with long half-lives need to be taken less frequently, which is crucial to avoid excessive sedation and other side effects.

What are the three key phases of drug action mentioned in the lecture?

The three key phases of drug action are onset (when the drug starts to take effect), peak (when the drug reaches its highest concentration at the target site), and duration (how long the drug has a physiological effect).

What is the difference between a therapeutic effect and a side effect?

A therapeutic effect is the desired effect of a drug for treating a disease or symptom, while a side effect is an undesired effect that may occur in addition to the therapeutic effect.

Why is it important to monitor blood levels of certain medications like antibiotics and anticonvulsants?

Monitoring blood levels is important to ensure the drug concentration remains within the therapeutic range. If the level is too low, the drug may not work effectively; if too high, it can cause toxicity.

What is ototoxicity, and which drug is known to cause it?

Ototoxicity is ear poisoning that can result from exposure to certain drugs, leading to hearing loss or balance issues. Gentamicin, an antibiotic, is known to cause ototoxicity.

How can nephrotoxicity be monitored, and which common drugs may cause it?

Nephrotoxicity, or kidney damage, can be monitored by evaluating blood tests like BUN (blood urea nitrogen). Non-steroidal analgesics like ibuprofen or Motrin are examples of drugs that may cause nephrotoxicity.

What are adverse reactions, and how are they different from side effects?

Adverse reactions are severe side effects such as death or shock, which are much more serious than common side effects like nausea or constipation. Adverse reactions often require a change in medication.

What are the potential side effects of drugs on the nervous system?

Potential side effects of drugs on the nervous system include agitation, confusion, delirium, depression, drowsiness, decreased respiration, and coma.

Why is it important for healthcare professionals to assess patients before administering medications?

It is important to assess patients before administering medications to obtain baseline data, such as blood work and vital signs, to ensure proper absorption and distribution of the drug and to monitor for any potential problems.

Outlines

00:00

💊 Understanding Drug Half-Life and Effects

This section explains the basics of drug elimination from the body, focusing on the concept of half-life, which is the time required for the body to eliminate 50% of a drug. An example is given using a 100 mg dose with a 12-hour half-life. The discussion also covers the importance of half-life in drug administration, especially in geriatric patients, and introduces key terms like onset, peak, and duration of drug effects. The section highlights the need to understand therapeutic levels, side effects, and the potential for toxicity, with examples of ototoxicity and nephrotoxicity caused by certain drugs.

05:03

⚠️ Managing Drug Side Effects and Adverse Reactions

This section delves into the potential side effects and adverse reactions of medications, distinguishing between mild side effects (e.g., nausea) and severe adverse reactions (e.g., anaphylactic shock). It emphasizes the importance of recognizing and managing these reactions, with particular attention to hypersensitivity and idiosyncratic reactions. The text also explores the systemic side effects drugs can have on various organs, including the liver, kidneys, nervous system, and gastrointestinal system. Specific examples of drugs that can cause damage to these organs are provided, alongside strategies for monitoring and mitigating these risks.

Keywords

💡Half-life

Half-life is the time required for the concentration of a drug in the body to be reduced by half. It is a critical measure used to determine dosing intervals. For instance, if a medication has a half-life of 12 hours, it means that 12 hours after taking the dose, half of it remains active in the bloodstream. This concept is important for understanding how often a medication needs to be administered to maintain its therapeutic effects.

💡Therapeutic level

The therapeutic level is the concentration of a drug in the bloodstream that achieves the desired effect without causing toxicity. Maintaining a drug within its therapeutic range ensures efficacy while minimizing side effects. For example, monitoring the blood levels of antibiotics or anticonvulsants helps ensure they are effective and not harmful to the patient.

💡Side effect

Side effects are unintended effects of a drug that occur in addition to the desired therapeutic effect. While some side effects, such as nausea or vomiting, can be mild and managed with dietary adjustments, others can be severe and require a change in medication. Understanding side effects is crucial for healthcare professionals to manage and mitigate these unintended reactions.

💡Adverse reaction

An adverse reaction is a severe, unexpected, and potentially life-threatening response to a medication. Unlike mild side effects, adverse reactions require immediate attention and often necessitate discontinuation of the drug. Examples include anaphylactic shock or severe allergic responses, which can cause respiratory distress or cardiovascular collapse.

💡Ototoxicity

Ototoxicity refers to ear poisoning, which can result from exposure to certain medications, leading to hearing loss, dizziness, or tinnitus. The antibiotic gentamicin is cited as a drug that can cause ototoxicity. Understanding which drugs have ototoxic potential is important for preventing permanent hearing damage in patients.

💡Hepatotoxicity

Hepatotoxicity is the potential for a drug to cause damage to the liver. Medications like acetaminophen can lead to liver damage if their byproducts accumulate and overload the liver's detoxification pathways. Symptoms such as jaundice indicate liver impairment, making it essential for healthcare providers to monitor liver function in patients taking hepatotoxic drugs.

💡Idiosyncratic reaction

An idiosyncratic reaction is an uncommon and unpredictable response to a drug that occurs in a small number of patients. These reactions are not dose-dependent and are often due to genetic differences in drug metabolism. Managing idiosyncratic reactions involves recognizing them early and adjusting treatment plans accordingly.

💡Anaphylactic reaction

An anaphylactic reaction is a severe and life-threatening allergic response to a drug, characterized by symptoms such as difficulty breathing, rapid pulse, and swelling. It is a medical emergency requiring immediate intervention. Patients with known anaphylactic reactions are advised to inform healthcare providers and wear medical alert bracelets.

💡Pharmacology

Pharmacology is the branch of medicine that focuses on the study of drugs, including their actions, effects, metabolism, and excretion. This lecture highlights the importance of understanding pharmacological concepts, such as drug half-life, therapeutic levels, and side effects, to ensure safe and effective medication administration.

💡Nephrotoxicity

Nephrotoxicity refers to kidney damage caused by certain medications, leading to impaired kidney function. Drugs like ibuprofen can cause nephrotoxicity, and healthcare providers monitor kidney function through blood tests such as blood urea nitrogen (BUN) to detect and prevent potential kidney damage in patients.

Highlights

Introduction to drug actions and effects, focusing on drug elimination through metabolism and excretion.

Explanation of half-life: time required for 50% of a drug to be eliminated from the body.

Example of half-life: A medication with a 12-hour half-life reduces from 100 mg to 50 mg in 12 hours.

Importance of half-life in dosing frequency, particularly in geriatric populations.

Definition of onset, peak, and duration in relation to drug concentration and physiological effects.

Significance of reaching a therapeutic level to achieve the desired effect while avoiding side effects.

Monitoring drug levels in the bloodstream for medications like antibiotics and anticonvulsants.

Explanation of toxicity and its potential for causing permanent damage, such as ototoxicity and nephrotoxicity.

Relationship between ear and kidney tissue, leading to potential ototoxic and nephrotoxic effects.

Discussion of hepatotoxicity, including symptoms like jaundice and the risk posed by acetaminophen.

Overview of common side effects versus allergic reactions, with a focus on patient education.

Description of severe side effects and adverse reactions, such as anaphylactic reactions requiring emergency care.

Potential side effects on various body systems, including the nervous, GI, urinary, and hematology systems.

Importance of monitoring fluid and electrolyte imbalances when administering diuretics.

Emphasis on understanding drug administration for proper absorption, distribution, and excretion.

Transcripts

This is the lecture covering the basics of pharmacology part 2. In this section

we're going to review drug actions and effects. Drugs are eliminated from the

body by metabolism and excretion. A measure of time required for elimination

is called half-life half-life which is defined as the time it takes for fifty percent

of the drug to be eliminated from the body. An example of half life would be if

you would give 100 milligrams of medication at noon on Monday of a

medication that has a half-life of 12 hours. 12 hours later at midnight on

Monday, 50 milligrams of that medication is still available in the bloodstream. At

noon on Tuesday, 25 milligrams is still in the system and so on. As you can

imagine, a medication with a long half-life will need to be taken less

frequently. This is an important consideration with our geriatric

population, especially when we consider medications like diazepam or valium that

cause sedation and have a long half-life.

All drugs have an onset, peak, and duration. Onset is when the drug has arrived to

the target spot and the concentration of the medication is enough to start a

response. Peak is the time when the drug reaches its height concentration on the

target receptor sites. Duration is how long the drug has physiological effect.

It's also crucial as allied health professionals to know the desired action

and side effects of each medication prior to administration and the antidote

if one is available. The goal for medication administration is to reach a

therapeutic level. A drugs therapeutic level or therapeutic effect is the

desired effect for treating a disease or symptom, while a drug side effect is an

undesired effect on the patient. When a drug is in the bloodstream, sometimes a

blood sample may be drawn to determine

the amount of drug in the system. It's

important that certain drugs like antibiotics and anticonvulsant be

measured to ensure that the drug blood level is within the therapeutic range.

If our drug level is too low, it doesn't work, if it's too high, toxicity can occur.

Medications may become toxic and cause permanent damage Ototoxicity is quite

simply ear poisoning which may be the result from exposure to drugs. Such

damage can lead to temporary or permanent hearing loss and or loss of

balance. The antibiotic gentamicin is one of these drugs that can cause

ototoxicity. Patients can complain of hearing loss, vertigo, or dizziness and

tinnitus or ringing in the ear. Other medications like non-steroidal analgesics

like ibuprofen or motrin can cause nephrotoxicity and damaged kidney

function. If kidney damage is suspected we can monitor blood tests such as the be

BUN or blood urea nitrogen to evaluate kidney function. Here's an interesting fact.

Did you know that the ears and the kidneys are derived from the same tissue

during fetal formation so this is why some medications may be ototoxic and

nephrotoxic. You know, other medications can be toxic to the liver which is

hepatotoxicity. Jaundice or yellowing of the skin and eyes may be seen.

When a medication is approved and goes on the market, the drug manufacturer has

to list all its known side effects. You know every medication has side effects

and these are usually mild and allows the patient to continue taking the medication.

Nausea, vomiting and constipation are examples of this.

Many times we can work with these side effects by changes to the diet or

activity. I have had patients though who stated they were allergic to medications

and when I asked them, they said it made them nauseated. Nausea is not an allergic

response but a side effect. Okay, on the other hand now we have adverse reactions and these

are severe side effects such as death or shock. The physician will certainly

change the medication in this instance! You might note that in some of your

nursing drug books the common side effects will be underlined and the

adverse effects will be in red.

At times a patient will have an idiosyncratic reaction or a rare and

unique side effect. This effect must also be managed. Allergic reactions or

hypersensitivity can occur with patients and can cause urticaria or

hives. If this reaction is mild the patient is warned to not take this

medication again. Occasionally though a patient can have a life-threatening

reaction that causes respiratory distress and cardiovascular collapse

this is known as an anaphylactic reaction and is a medical emergency!

Patients are warned to tell all healthcare practitioners about this and

wear a medical alert bracelet that explains this allergy. So let's briefly

look at the systems and the kind of side effects that we might see with our body

systems so when a medication affects the nervous system again we must watch for

serious side effects. Side effects can include agitation, confusion, delirium,

depression, drowsiness, decreased respiration, and coma. As we discussed

earlier, the liver is one of the major organs that metabolizes medications.

If drugs accumulate in the liver it can cause permanent damage. Acetaminophen or

Tylenol as its brand name is one such drug. Liver damage is the most serious

side effect of acetaminophen and it can be fatal. Here's how it goes...

acetaminophen is broken down in the liver and it creates several by-products.

These byproducts build up but if the byproducts then builds up in the

liver the pathway that eliminates these byproducts is overloaded and the liver

must use another path to remove them. When this happens a toxic compound

called na pqi is made and this is what causes liver damage. You know the GI

system suffers probably the most from medications. Many medications can cause

nausea and vomiting. For some reasons it could be that medications irritate the stomach.It

can affect the inner ear they may cause dizziness and this can cause

nausea. They may also slow down intestinal movement and make you feel

bloated and sick to your stomach. Many times we can work with these symptoms

depending on the medication. Other GI symptoms are of course vomiting, anorexia,

diarrhea, constipation, and stomach ulcers.

Some medications affect the urinary system especially our diuretics commonly

known as water pills. Fluid and electrolyte imbalances may occur so

those do need to be monitored. Certain drugs can also affect the hematology

system and cause problems with poor coagulation of blood. Bleeding, clotting,

and immunosuppression side effects may be decreased red blood cells, white blood

cell,s and platelets. With the decrease in red blood cells, the patient will become

anemic leading to fatigue and weakness. A decrease in white blood cells can make

the patient prone to infections. With decreased platelets, control of bleeding

can be challenging. You know some medication such as warfarin, Coumadin is

the brand name; these medications are designed to decrease clotting so blood

levels have to be done to evaluate clotting routinely. The key to

pharmacology is to get the most effective medication with the least

amount of problems. We must understand these medications that we administer, and

there possible effects,,, good and bad. Before we give medications, assessment

of the patient is necessary to obtain baseline data. Assessing the blood work

and vital signs may be necessary prior to administration. We as healthcare

professionals, we must be really vigilant about knowing how to best administer a

drug for proper absorption into the blood. We should also know how the drug is

distributed and what symptoms or lab tests results to watch for that may show

a potential problems. Understanding how drugs are excreted and the chance of

accumulation is also critical.

You know, we are the patient's advocate!

This concludes part two of basics of pharmacology. If you have any questions

bring them to the Pharm Cafe or to the classroom!