14 - Pharmacology (Pharmacodynamics)

Define Pharmacodynamics.

Define Pharmacodynamics.

• Drug response

• Drug concentrations and its effects on the body

Define Primary effect.

The desired response (effect) from the drug

Define Secondary effect.

• Desirable or undesirable effect

• A drug may be used for its secondary effect (telling someone to take Benadryl for sleep)

Example: Benadryl

• Primary effect: rids of sneezing and coughing

• Secondary effect: drowsiness

Define Dose Response.

• Relationship between minimal and maximum dose of a drug that is needed to produce the desirable effect

• Some people need higher dosages than others to feel the same effect

What is a rule of administration?

• Based on dose response (everyone is unique and may need different amounts to feel same affect)

• Do not start high, begin with a low dose and then titrate up

What are some factors that affect absorption for IM?

• Perfusion or blood flow to tissue

• Amount of fat

• Temperature of tissue →

  • Cold → dec absorption

  • Heat → inc absorption

What are some factors that affect PO absorption?

• Acidity of stomach

• Length of time stomach

• GI health and blood flow

• Food present → higher acidity → stomach empties slower → drug in acidic environment for longer

• Milk, alcohol, and protein → inc stomach acidity

What are some factors that affect Mucous Membrane (sublingual and buccal) absorption?

• Perfusion or blood flow

• Integrity of mm

• Presence of food or smoking

• Length of time retained in area

• Correct placement

What are some factors that affect topic or intradermal (skin) absorption?

• Perfusion or blood flow

• Integrity of skin

• Ability to med to adhere to skim

• Adequacy of SQ tissue

What are some factors that affect the absorption of inhaled drugs?

• Perfusion or blood flow

• Integrity of lung lining

• Proper administration

• Inspiratory effort

Define Maximal Efficacy.

• The maximum response that is achievable from a drug

• Example

  • Morphine has maximal efficacy > Tylenol (stronger)

Define Onset action.

Time it takes to reach minimum effective concentration of drug

Define Peak action.

• When the drug reaches its highest blood or plasma concentration

AOT (give your heart to the cause🫡)

Why is it important to understand onset, peak, and duration?

• Maintain constant blood level of drug within safe therapeutic range

• Setting drug schedules

• Obtaining goals

What is an Agonist?

Produces an effect

• Morphine binds to opioid sites → acts like natural endorphins → pain relief

• Too much binding → causes overdose

What is an Antagonist?

Blocks the effect

Naloxone (Narcan) → binds to opioid sites → blocks effects of morphine and other opioids

What is Therapeutic index?

Estimates the margin of safety of a drug

What is Therapeutic Range?

Looks at the serum drug concentration

• Sufficient enough to be effective

• Peak serum concentration below toxicity level

Define a medications trough level when drawn.

• Lowest plasma concentration of the drug

• Measures elimination rate

• Drawn immediately before or 30 mins before next dose

Define a medication’s peak level when drawn.

• Highest plasma concentration of the drug at a specific time

• Indicates absorption

• Drawn 1 hr after dose

Why must we monitor peaks and troughs for some drugs?

• They have a narrow therapeutic window

• Too low → won’t work

• Too high → toxic

• Ex: Digoxin

  • CHF

  • Very toxic - narrow therapeutic range

  • Reduces HR

  • Inc cardiac output

What are side effects?

• Physiological effects not related to the desired effect of the drug

• All meds have side effects

• Usually mild such has itching or drowsiness

• Severe such as N/V

What are adverse effects?

• Always serious and/or life threatening

• Always undesirable

• MUST be reported and documented

Examples:

• Anaphylaxis, hepatotoxicity, nephrotoxicity

• Killing an organ

What are toxic effects?

• Occurs from overdose or accumulation of drug

• Identified by: s+s

• Confirmed by: serum drug levels (peaks and troughs)

What are drug interactions?

• Interactions that occur when the action of one drug is modified by another food or drug

• Can be positive: additive effect, synergism

• Or negative: interference and incompatibility

What is an example of an additive drug interaction?

Tylenol and Codeine combined provider greater pain relief than Tylenol or Codeine alone

What is an example of synergism (potentiation) drug interaction?

Morphine and Hydroxyzine potentiate each other → increased pain relief

What is an example of a interference drug interaction?

Benemid (medicine used for gout) slows rental excretion of penicillin → toxicity

What is an example of incompatibility drug interaction?

• Magnesium in antacids inactivates tetracyclines

• Black precipitate in syringe

What is a drug that is potentially renal toxic?

Aminoglycosides

• Must monitor carefully

• Labs:

  • Serum drug levels

  • Creatinine

  • Creatinine clearence

  • Urine output

When teaching a patient about OTC drugs, which points should the nurse include?

1. These drugs are very safe and can be used freely to relieve your complaints.

2. These compounds are called drugs, but they aren’t really drugs.

3. Many of these drugs were once prescription drugs but are now thought to be safe for use without a prescription when used as directed.

4. Reading the label of these drugs is very important; the name of the active ingredient is prominent; you should always check the ingredient name.

5. It is important to read the label and to see what the recommended dose of the drug is; some of these drugs can cause serious problems if too much of the drug is taken.

6. It is important to report the use of any OTC drug to your health care provider because many of them can interact with drugs that might be prescribed for you.

3, 4, 5, 6

A patient asks what generic drugs are and if they should be using them to treat his infection. Which of the following statements should be included in the nurse’s explanation?

1. A generic drug is a drug that is sold by the name of the ingredient, not the brand name.

2. Generic drugs are always the best drugs to use because they are never any different from the familiar brand names.

3. Generic drugs are not available until the patent expires on a specific drug. Generic drugs are usually cheaper than the well-known brand names, and some insurance companies require that you receive the generic drug if one is available.

4. Generic drugs are forms of a drug that are available over the counter and do not require a prescription.

5. Your physician may want you to have the brand name of a drug, not the generic form, and DAW will be on your prescription form.

6. Generic drugs are less likely to cause adverse effects than brand name drugs.

1, 3, 4, 6

When trying to determine why the desired therapeutic effect is not being seen with an oral drug, the nurse should consider

a. the blood flow to muscle beds.

b. food altering the makeup of gastric juices.

c. the weight of the patient.

d. the temperature of the peripheral environment.

B

When reviewing a drug to be given, the nurse notes that the drug is excreted in the urine. What points should be included in the nurse’s assessment of the patient?

a. The patient’s liver function tests

b. The patient’s bladder tone

c. The patient’s renal function tests

d. The patient’s fluid intake

e. Other drugs being taken that could affect the kidney

f. The patient’s intake and output for the day

a, c, e

When considering the pharmacokinetics of a drug, what points would the nurse need to consider?

a. How the drug will be absorbed

b. The way the drug affects the body

c. Receptor site activation and suppression

d. How the drug will be excreted

e. How the drug will be metabolized

f. The half-life of the drug

a, d, e, f

Drug–drug interactions are important considerations in clinical practice. When evaluating a patient for potential drug–drug interactions, what would the nurse expect to address?

a. Bizarre drug effects on the body

b. The need to adjust drug dose or timing of administration

c. The need for more drugs to balance the effects of the drugs being given

d. A new therapeutic effect not encountered with either drug alone

e. Increased adverse effects

f. The use of herbal or alternative therapies

b, e, f

A client is experiencing a reaction to the penicillin injection that the nurse administered approximately ½ hour ago. The nurse is concerned that it might be an anaphylactic reaction. What signs and symptoms would validate the nurse’s suspicion?

a. Rapid heart rate

b. Diaphoresis

c. Constricted pupils

d. Hypotension

e. Rash

f. Client report of a panicky feeling

a, b, e, f

A patient is taking a drug that is known to be toxic to the liver. The patient is being discharged to home. What teaching points related to liver toxicity and the drug should the nurse teach the patient to report to the physician?

a. Fever; changes in the color of urine

b. Changes in the color of stool; malaise

c. Rapid, deep respirations; increased sweating

d. Dizziness; drowsiness; dry mouth

e. Rash; black or hairy tongue; white spots in the mouth or throat

f. Yellowing of the skin or the whites of the eyes

a, b, f