Mid-Term Summary & Study Guide

NURS-6521

 100-question Exam which will assess your knowledge on the Learning Resources from Weeks 1-6.

 Time limit of 2 hours.

 Multiple choice or multiple selection.

Pharmacodynamics: how the drug effects the body

Pharmacokinetics: how the body effects the drug

 Understand the implications of changing renal function on creatinine & drug dosing.

Kidney/Renal functions :

 Filters blood = Remove Waste, Toxins, and Extra Fluid from the body

 Returns needed substances to the blood – & the remainder becomes urine

 Removes acid produced by cells of the body to maintain balanced water, salts; minerals

 Makes hormones that control BP, make RBCs; keeps bones strong

Creatinine: Measures kidney function - byproduct of muscle metabolism (creatinine phosphate)

Normal Serum Creatinine levels: 0.6-1.3 mg/dL - healthy kidney (Easily filters & excretes creatinine)

More Reliable than BUN. Creatinine is Not Absorbed by the kidneys.

Rises indicate renal damage or failure = Kidney is unable to properly filter & excrete waste (creatinine) = Lab

Value rises in the serum.

 Creatinine =  Kidney Function = Requires a decreased dose of medication or different dosing schedule

= Renal Dosing

 What is the impact of the following on drug levels and dosing:

 Cirrhosis: a disease in which normal liver cells are replaced by scar tissue.

As liver cells die, the organ makes less of the proteins that regulate fluid retention & blood clotting and

the liver loses its ability to metabolize the pigment bilirubin.

Liver/Hepatic functions :

 Produces proteins that help clot blood

 Removes / neutralizes poisons, drugs and alcohol

 Manufactures bile that helps the body absorb fats & cholesterol

 Helps maintain normal blood sugar levels

 Regulates hormones

With Cirrhosis - the liver fails to detoxify the blood & it becomes less able to metabolize medications, which

magnifies their effects. Eventually toxins build up in the brain & can produce:

 Increased sensitivity to drugs

 Levels of medication will be higher d/t decreased metabolism

 Requires decreased dose of medication

 Liver/Hepatic Function =  Ability to metabolize medication = Requires a decreased dose of

medication or different dosing schedule = Hepatic Dosing

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 Protein binding: Drugs can form reversible bonds with various proteins in the body.

Plasma albumin is the most important - large molecule - too large to leave the bloodstream!

Binding is reversive & Drugs can be bound or unbound.

% of drug molecules that are bound is determined by the attraction between it and albumin.

Ex. Albumin & Warfarin – Strong Attraction =

99% of warfarin molecules in plasma are bound. 1% Free.

 Albumin & Antibiotic Gentamicin – Weak Attraction =

< 10% of gentamicin molecules in plasma are bound. > 90% Free.

 Restricted drug distribution = Albumin is too large to leave; bound molecules cannot leave either!

o Bound molecules cannot reach their site of action or undergo metabolism/excretion until drug-protein bond is

broken so the is free to leave the circulation.

 Drug Interactions = Each Albumin molecule has only a few sites where drug molecules can bind.

o Drugs will complete with 1 another for the limited binding sites = 1 drug displaces another from albumin = Free

concentration of the displaced drug Rises = Increasing intensity of drug responses!

o If plasma drug levels rise = Toxicity!

o If the drug is highly protein bound = Need higher dose of drug to attach to/saturate all areas of the drug

binding proteins & the Receptors TO GET RESULTS!

o If you have Drug A in place at all drug binding protein sites, and you add Drug B (which is more protein

bound), it will displace (Kick off) Drug A & take their place at the drug binding protein sites = Causing

more Drug A to be free floating

o Ex: Coumadin & Dilantin Both Highly Plasma Protein Bound Drugs!

o 3 days prior to surgery, Coumadin in stopped – leaving more protein binding sites for Dilantin. The

Dilantin binds and leaves less available to prevent Seizure

o Starting or stopping drugs that bind to plasma protein changes the free drug levels of other protein

bound drugs *Check Levels & Drug Effects more frequently!

 Drug interactions: When two drugs interact, there are three possible outcomes:

(1) one drug may intensify the effects of the other

(2) one drug may reduce the effects of the other

(3) the combination may produce a new response not seen with either drug alone.

• Medications must be prescribed at doses that will allot for the appropriate level of outcome required

specifically for that patient.

• Frequent monitoring of effects & levels are required

 Half-life: the time required for the amount of drug in the body to decrease by 50%.

Metabolism & excretion cause the drug in the body to decline.

Half-life of a drug determines the dosing interval (i.e., how much time separates each dose).

Short half-life = Dosing interval must be correspondingly short or therapeutic effects will be lost.

Long half-life = Long time can separate doses without loss of benefits.

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 No matter what the amount of drug in the body may be, half (50%) will leave during a specified time period (the

half-life).

 The actual amount of drug that is lost during one half-life depends on just how much drug is present: the more

drug in the body, the larger the amount lost during 1 half-life.

Routes of Administration and Dosage Forms:

 Understand when it is OK to crush (or not crush) certain dosage forms & why.

 OK to Crush: Immediate Release

 Not OK to Crush: Sustained Release/ Enteric Coated

 Immediate Release: Rapid absorption of a drug after ingestion ( < 30 minutes )

 Extended-Release: Released over a period of time ( 8, 12, 24 hours)

o Sustained Release: Maintains drug release over a sustained period but not at a constant rate

o Controlled Release: Maintains drug release over a sustained period at a nearly constant rate

*prolongs actions but also attempt to maintain therapeutic drug levels

 Delayed Release: Releases the dose after a set time. Usually enteric coated to prevent release in the

stomach – it releases the dose in the intestinal track.

 Which Routes of administration have the fastest and slowest rates of absorption?

o Fastest to Slowest: IV, IM, SC, Oral

o IV, Inhaling, Snorting, Smoking, Swallowing, Rectal

o IV, IM, Intranasal, Intradermal, Subcutaneous, Oral, Rectal

Oral forms: Time until a pill/capsule is broken down enough to release the medication in the stomach:

Crushed/Chewed Tablet = under 10 mins

Chalk tablet = 10 mins & Solid tablet = 10 mins

Time-release capsule = 45 minutes

Gel capsule = > 60 mins

ENTERAL ROUTE: to the GI/ Intestinal Tract

• Oral: By Mouth: PO: Easiest & most economical way. Avoid if pt is lethargic, has N/V, or unable to

swallow/NPO [Involves 1st pass effect – decreasing concentration rapidly before hits target]

• Sublingual: Under Tongue to dissolve. Absorbed through the mucous membranes of the gums, Not to be

Swallowed. No water until dissolved fully.

• Buccal: Between the gum and cheek. Rotate sides to avoid irritation.

• Rectal: Suppository or Enema: When unable to take oral meds. Avoids about 2/.3 of first-pass

metabolism.

• Tubes: NG/Duodenal/G-Tubes: Meds needs to be crushed, so confirm orders!

MUCOUS MEMBRANE ROUTE:

• Transdermal: Patch: Through the skin. Left for extended time, Extended release meds are used for

longer effect.

• Drops/Sprays: Via Eyes, Nose, or ears. Absorbed through Mucous Membranes, Can Cause Systemic

Effects. Confirm # of drops/sprays to be administered.

• Vaginal: Can cause irritation to the mucous membranes.

TOPICAL ROUTE:

• Eye/ Nasal Mucosa/ Skin: Usually less lipophilic to reduce systemic absorption.

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