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Pharmacology Week 2 Cheat Sheet by

nursing     pharmacology

CNO Practice Standard: Medication

Safe, effective, and ethical admini­str­ation
Knowledge, technical skill, and judgement required
Ongoing mainte­nance of competence

Evaluation

System­atic, ongoing, and dynamic part of the nursing process
Determ­ining status of goals and outcomes of care
Monitoring patient's response to drug therapy (Thera­peutic, expected, toxic responses)
Clear, concise docume­ntation

Drug Absorption of Various Oral Prepar­ations

Fast­est
Liquids, elixirs, syrups
 
Suspension solution
 
Powders
 
Capsules
 
Tablets
 
Coated tablets
Slow­est
Enteri­c-c­oated tablets

Pharma­cok­inetic Phase: First-pass effect

The metabolism of a drug and its passage from liver into circul­ation
Oral drugs are absorbed from intestinal lumen into mesenteric blood system, and go to the liver by means of portal vein
Once in the liver, it is metabo­lized by P450 enzyme system and passed into general circul­ation
If large amount of drug is metabo­lized to an inactive form, then less is available in circul­ation (high first-pass effect)
Means that most drugs have bioava­ila­bility of <100%, whereas same drug given IV is 100% bioava­ilable because it has not been metabo­lized by the liver
- A drug given via oral route may be extens­ively metabo­lized by the liver before reaching systemic circul­ation (high-pass effect)
- Same drug given IV bypasses liver, preventing the first-pass effect from taking place, and more drug reaches circul­ation
- ie. Nitro

Pharma­cod­yna­mics: Mechanism of Action

Receptor Intera­ction
Drug reacts with a site on the surface of a cell or tissue to elicit­/block a physio­logical response
Receptor agonist
Elicit response from the cell
Receptor antago­nist
Do not elicit response (block usual physio­logical response)
Enzyme intera­ction
Drug inhibi­ts/­alters physio­logical response of enzyme; fools cell to attach to it VS its targeted cells
Non-­spe­cific intera­ction
Drugs interfere with or chemically alter cellul­ar/­met­abolic processes
Drugs produce their actions through 1 of 3 primary mechanisms of action: Receptors, enzymes or non-sp­ecific intera­ction

Receptor Intera­cti­on: Drugs will have affinity to bind to particular receptor – good fit and strong affinity means greatest response

Pharma­cot­her­ape­utics: Nursing respon­sib­ility

Asse­ssm­ent:
- Current medication
- Pregnancy
- Breast feeding
- Concurrent illnesses
- Allerg­ies­/se­nsi­tiv­ities
- Contr­ain­dic­ati­ons: Make the use of the drug very dangerous

Impl­eme­nta­tion:
- Intent of the therapy, as well as the psycho­-motor skill of admini­stering
- Acute therapy
- Mainte­nance therapy
- Supple­mental therapy
- Palliative therapy
- Prophy­lactic therapy

Moni­tor­ing:
- Client's condition
- Side effects (predi­ctable)
- Adverse effect­s/r­eaction (serious)
- Toxic effects
- Intera­ctions

Eval­uat­ion:
Reasse­ssing client's condition and therap­eutic effect­iveness of pharac­oth­erapy
Inte­rac­tions - Alteration of drug action by:
- Other prescribed drugs
- Over-t­he-­counter medica­tions
- Herbal therapies
- Food or alcohol intera­ctions

Drugs and Breast­feeding

Many drugs pass into breast milk
Lower than in maternal circul­ation
Depends on drug properties (lipid solubi­lity, concen­tra­tion, etc.)
Must consider the harm-b­enefit ratio

Drugs and Children

<38 weeks gestation
Premature or preterm infant
<1 month
Neonate or newborn infant
1month - 11months
infant
1 year - 12 years
Child
13 years - 19 years
Adolescent
Important to weigh in kg as doses often weight and/or body surface area based
 

Pharma­col­ogical Principles

Phar­mac­eut­ics
Science of preparing and dispensing drugs, including dosage form and design (ie. Tablets, patches, capsules, inject­ions)
Phar­mac­oki­net­ics
What the body does to the drug (Absor­ption, distri­bution, metabo­lism, excretion)
Phar­mac­ody­nam­ics
What the drug does to the body (bioch­emical and physio­logical intera­ctions)
Phar­mac­oth­era­peu­tics
Use of drugs and clinical indica­tions for drugs to prevent and treat disease
Phar­mac­ogn­osy
Study of natural plant and animal drug sources

Phases of Drug Activity

I. Pharma­ceu­tical Phase
Disint­egr­ation of dosage form
II. Pharma­cok­inetic Phase
Absorp­tion, distri­bution, metabo­lism, excretion
III. Pharma­cod­ynamic Phase
Drug-r­eceptor intera­ction
Phar­mac­eutical phase - becomes available for absorption once admini­stered
Phar­mac­oki­netic phase - drug is being manipu­lated by body and becoming available for action
Phar­mac­ody­namic phase - drug having desired effect on target

Pharma­ceu­tical Phase

80% of drugs are PO
Solutions absorbed faster than solids
Absorbed faster in acidic fluids than alkaline fluids
Young and elderly have less gastric acidity - drug absorption is generally slower
Food may increa­se/­dec­rease absorption

Pharma­cok­inetic Phase: Absorption

Abso­rpt­ion
Process of drug leaving the site of admini­str­ation and becoming avail­able
bioa­vai­lab­ility speaks to extent of drug that is actually absorbed in blood stream

Factors that affect absorp­tion:
Most oral drugs absorbed in small intestine
- Admini­str­ation route of drug
- Food or fluids admini­stered with drug
- Dosage formul­ation
- Status of absorptive surface
- Rate of blood flow to small intestines
- Acidity of stomach
- Status of GI motility

Pharma­cok­inetic Phase: Distri­bution

Dist­rib­ution
Drugs are distri­buted throughout body by blood stream
Dist­rib­ution influenced by:
- Blood flow
- Affinity to tissues
- Protei­n-b­inding (if drug binds to protein, they're less likely to be able to leave circul­atory system, therefore not reach target tissue. Higher protei­n-b­inding of drug = slower its action will be. Albumin is most common blood protein drugs bind to. Portion of drug that is unbound and active is the "­fre­e" drug. Free drug increases risk of toxicity)
- Volume of drug distri­bution

Pharma­cok­inetics Phase: Metabolism

Biot­ran­sfo­rma­tion: Primarily Liver (also skeletal muscle, kidney, plasma, lungs)
Process of transf­orming a drug into inactive metabolite (more soluble compound)
Cyto­chrome P-450 enzymes most respon­sible for biotra­nsf­orm­ation
Hepatic biotra­nsf­orm­ation varies (genetics, diseases, other drugs, etc.)
Delayed drug metabolism results in accumu­lation of drugs in system - prolonged action time

Pharma­cok­inetics Phase: Elimin­ation

Elimin­ation of drugs from body
Excrete through kidney (main organ)
Other routes: liver, bile feces, lungs, saliva, sweat, breast milk
Whether active or inactive metabo­lites, all the waste products have to be eliminated

Prescr­iption Drugs

Food and Drug Regula­tions (Schedule F)
Lists drugs that must be sold by prescr­iption

Drugs and Pregnancy

First trimester generally period of greatest danger
Transfer to fetus primarily by diffusion across placenta and some active transport
Factors that contribute to safety include drug proper­ties, gestat­ional age, and maternal factors

Drugs and the Older adult

65 years or older
Poly­pha­rmacy
Consumes 20-40% of Rx drugs, 40% OTC drugs
Risk of drug intera­ctions
Refer to table 4.4 p. 68-69 for proble­matic drugs
 

10 Rights of Medica­tions

Right drug
Right dose
Right time
Right route
Right patient
Right reason
Right docume­ntation
Right evaluation
Right patient education
Right to refuse

Drug Names

Chemical Name
Drug's chemical compos­ition and molecular structure
Generic Name
Name given by Health Canada under FDA and FDR
Trade name
Drug has registered trademark; use of name restricted by drug's patent owner

Pharma­cok­inetic Phase: bypassing the liver

Sublingual
Buccal
Rectal
Intrav­enous
Intranasal
Transd­ermal
Vaginal
Intram­uscular
Subcut­aneous
Inhalation
- Routes do not require absorption within GI tract, therefore bypassing the liver and do not experience effect of "­fir­st-pass effect:
- Rectal route undergoes higher degree of first-pass effects than other routes listed

Pharma­cok­ine­tics: Half-life of a Drug

Time it takes for one half of the original amount of a drug to be eliminated from the body
Metabolism and elimin­ation affect the half-life of a drug
Useful for determ­ining 'steady state'
After ~5 half-l­ives, most drugs are considered to be removed from the body (97%)

Pharma­cok­ine­tics: Steady­-State

Amount of drug eliminated is equal to amount absorbed at each admini­str­ation
Steady­-state is desired to achieve a therap­eutic effect over time
Longer half-life = longer it takes to reach steady state

Pharma­cok­ine­tics: Onset, peak, duration

Onset
Time it takes to reach minimum effective concen­tration
Peak
Occurs when drug reaches highest blood or plasma concen­tration
Dura­tion
Length of time drug has a pharma­cologic effect

Other Drug-R­elated Effects

Tera­tog­enic
Disturb fetal/­embryo develo­pment
Muta­genic
Changes genetic material
Carc­ino­genic
Cancer­-ca­using

Drug Legisl­ation

Food and Drugs Act
- Protect consumer from drugs that are contam­inated, adulte­rated, or unsafe for use.
- Addresses drugs taht are labeled falsely and those with mislea­din­g/d­ece­ptive labels
Cont­rolled Drugs and Substances Act
- Addresses posses­sion, sale, manufa­cture, disposal, produc­tion, import, export, and distri­bution of certain drugs

Over-t­he-­Counter Drugs (OTC)

Rest­ricted Access Drug
- Must ask pharmacist (insulin, lopera­mide)
Pharmacy Only
ie. Antihi­sta­mines, ulcer meds
General Retail
ie. Acetam­ino­phen, nicotine gum
Criteria for OTC Status
- Consumer must easily diagnose condition and monitor effect­iveness
- Drug should have: favourable adverse affect, profile, limited drug intera­ction profile, low misuse potent­ional
- Drug should be easy to use and easy to monitor

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