Pharmacology.txt

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Danette
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Pharmacology.txt
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2012-04-17 01:30:11
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Pharmacology
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Pharmacology
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  1. Categories A-D & X
    • A. No risk to fetus
    • B. Little to no risk in pregnant women
    • C. Adverse effects demonstrated in animals
    • D. Human fetal risks have been demonstrated
    • X. Fatal risk clearly documented
  2. First pass
    Some drugs do not go directly into systemic circulation following oral absorption, but pass from the intestinal lumen to the liver via the portal vein.--The process in which a drug passes to the liver first is called first pass effect. --Some drugs metabolize to inactive form. (Lidocain) Drug is inactivated & excreted & cannot be given orally.
  3. Bioavailability
    • % of drug that reaches systemic circulation
    • % of meds available to the body
    • IV - 100% bioavailablity - released directly into blood stream - hasn't lost any potency
    • Oral - stomach - protal vein - liver = less than 100%
    • Oral meds can be 2-3x higher dosage than IV due to decreased bioavailability
  4. Half life
    • Time needed for the plasma concentration of a drug to be reduced by 50% after absorption.
    • Reduced by metabolism & excretion
    • A drug goes through several half-lives before more than 90% of the drug is eliminated.
    • A short half life is considered to be 4-8 hours & long, 24 hours or longer.
    • This is what determines drug dosing.
  5. Agonist
    Drug that produces a response --fits into receptor (morphine)
  6. Antagonist
    Will block agonist -- give narcan if you suspect morphine od
  7. Peak
    Highest plasma concentration of a drug --draw for peak 1 hour after Med is infused
  8. Trough
    Lowest plasma concentration of a drug & measures the rate at which the drug is eliminated
  9. Side effects
    Physiological effects not related to the desired drug effect--usually more of a minor problem
  10. Adverse reaction/effects
    Undesirable drug effects that range from mild unintended effects to severe toxic effects including anaphylaxis
  11. Additive
    • Same MOA
    • Sum of effects of 2 drugs with similar actions/categories

    • Desireable: When 2 drugs are given & even better control - diuretic + B blocker = effective BP control
    • Undesireable: 2 vasodilaers - severe hypotension
  12. Synergistic Effect
    • Different MOA
    • 1st drugs MOA potentiates or enhances the other causing an effect greater than when taken alone.

    • Desireable: Phenergen enhances Fentanyl - safer because you can give les drug
    • Desireable: Morphine & Narcon - antidotes
    • Undesireable: Alcohol & Sedatives - increases CNS depression
  13. Antagonistic effect
    2 drugs in opposing drug categories cancel drug effects of both drugs - Blocks

    Desireable: Morphine + Narcon - antidotes
  14. Possible causes & reasons for drug accumulation & toxicity
    Low protein decreases number of protein binding sites. Toxicity drugs that decrease cardiac output = decreased blood flow to kidneys = decreased GFR = decreased drug excretion = increased toxicity
  15. Low therapeutic index vs high therapeutic index
    • Drugs with low therapeutic index have a narrow margin of safety. Drug dosage might need adjustment & plasma drug levels need to be monitored.
    • Drugs with high therapeutic index have a wide margin of safety & less danger of producing toxic effects. Plasma levels do not need to be monitored.
  16. What happens when 2 highly protein-bound drugs are taken simultaneously?
    They compete for protein or albumin sites in the plasma. This results in a decrease in protein binding of 1 or both drugs, therefore, more drug circulates = drug toxicity.
  17. Action of enzyme inducers vs. enzyme inhibitors

    Part of Metabolism
    • Enzyme inducers: stimulate liver enzymes, increase metabolism, increase drug elimination & decrease plasma concentration = decreased drug action
    • Enzyme inhibitors - inhibit liver enzymes, decrease metabolism = increased plasma concentration = drug toxicity
  18. Duration
    length of time drug has pharmacologic effect
  19. Onset
    Time it takes to reach MINIMUM effectiveness
  20. Loading dose
    Large, initial dose given to achieve a rapid Minimum Effect Dose
  21. Drug Incompatibility
    Chemical or physical reaction of 2 or more drugs - syringe, IV bag, vial
  22. Bacterial Resistance
    Mutant growth despite antibiotic administration

    • *Inherent - no prior exposure - natural resistance
    • *Acquired - prior exposure - previously administered
    • *Cross - organism transference - transfer of resistance
  23. Nephrotoxocity
    • Renal damage
    • Monitor BUN & Creat before, during & after drug administration
  24. Hepatotoxicity
    Liver damage
  25. Ototoxicity
    Hearing damage
  26. Photosensitivity
    Cutaneous injury from sunlight exposure after medication administration
  27. Suprainfection
    • Secondary infection
    • Results from normal flora disruption from antibiotic use
    • Usually occurs with broad-spectrum antibiotic use >1 week
  28. Crystalluria
    • Crystals in the urine
    • Can lead to stones
  29. Key concepts of metabolism
    • Process by biochemical modification
    • *Enzymatic alteration of a drug molecule

    • Sites
    • *Primary - Liver
    • *Other - GI tract & lungs

    • Factors
    • *Liver function
    • *Protein binding
    • *Blood flow to the liver
    • *Age - hepatic immaturity
  30. Key concepts of excretion
    • Routes:
    • *Primary - kidneys/urine - EXCRETED in urine
    • --Unbound drugs
    • --H2O soluble drugs
    • --Unchanged drugs
    • *Other - hepatic, bile, feces, saliva, sweat, breast milk

    • Urine pH (4.5-8)
    • *Decreased pH - excretion of weak-base drugs
    • *Increased pH - excretion of weak-acid drugs

    Creatinine Clearance (85-135 ml/min)

    Glomerular Filtration Rate (GFR) - most drugs are FILTERED through here

    Look at creatinine - shows kidney function - if non-functioning, can lead to toxicity - drug doesn't get excreted - goes back into system

    • Drugs can increase or decrease excretion rate
    • *Drugs - decreased CO - decrease renal BF - decreased GFR - decreased excretion
    • *Drugs can compete for excretion

    • Renal or hepatic dysfunction - decreased drug metabolism & excretion
    • *Prolonged 1/2 life
    • *Increased "free drug" - toxicity
    • *Therapeutic monitoring of drug levels
  31. Considerations with placebo drug administration
    • Psychological benefit from a compound that may not have the chemical structure of a drug effect
    • *Effective in 1/3 of persons
    • *Clinical trial studies
    • --Informed consent requirements
  32. Considerations of schedule II medications
    • Account for all controlled drugs
    • Maintain controlled-substance record
    • Countersign all discarded/wasted portions
    • Ensure accuracy of records & available drugs
    • Ensure all controlled durgs are locked up; narcotics double-locked
    • Ensure only authorized persons have access
  33. Considerations with OTC medications
    • No Rx needed
    • *>90% of illnesses treated initially with OTC drugs

    • Side effects
    • *Interactions may be dangerous

    • Potential Disadvantages
    • *Delay in professional dx & tx
    • *Symptoms may be masked
    • *May interact w/ prescribed meds or other OTC meds
    • *Potential OD
    • *May increase side effects
  34. Considerations with the elderly
    • Concerns
    • Adverse drug reactions
    • *More severe
    • *More sensitive
    • Polypharmacy - administration of may drugs
    • Noncompliance - may fail to ask questions & regimen not understood or followed

    • Gastrointestinal
    • Decreased BF & motility - decreased GI function
    • Less gastric acidity - difficulty absorbing acidic drugs
    • Slower absorption of oral drugs
    • Delayed onset of action

    • Cardiac/Circulatory
    • Decreased CO - delayed distribution & decreased excretion
    • Decreased serum protein - increased "free drug"
    • Decreased body water - alteration of H2O-soluble drugs
    • Increased body fat & decreased muscle mass - alteration of lipid-soluble drugs

    • Hepatic
    • Decreased enzyme function & decreased BF
    • *Decreased metabolism
    • *Prolonged 1/2 life
    • *Drug accumulation

    • Renal
    • Decreased CO
    • Impaired renal function & GFR
    • Altered drug excretion - drug accumulation

    • Monitor renal function
    • *Urine OP
    • *BUN/Cr
    • *Cr clearance
    • *GFR

    • CNS & Physiologic sensitivity
    • *Drug dosing frequently must be reduced
    • *Selection carefully considered

    • Provide Education
    • *Assure for alternative devices - glasses/hearing aids
    • *Respectful manner
    • *Large legible print
    • *Review each medication with client
  35. Considerations with obtaining serum C&S
    • Should be drawn prior to antibiotic administration
    • Don't wait for results, give abx
    • Should be taken from 2 sites
    • Draw from 1st source, wait 15 minutes then draw from 2nd source
  36. Aminoglycosides: gentamicin (Garamycin)
    • Action
    • *Bactericidal
    • *Gram (-), E. coli, Kebsiella pneumoniae, Proteus, Pseudomonas, MRSA

    • Uses (IM/IV)
    • *Serious infections
    • *Pneumonia
    • *Pelvic inflammatory disease

    • Precautions
    • *Renal/hearing impairment

    • Med/Food Interactions
    • *Anesthesia - enhances NMB
    • *Penicillin
    • --PCN's decrease effectiveness
    • --Concurrent use - increased warafin (coumadin) effect
    • --Inactivate animoglycoside when admin. in same IV

    • Nursing Considerations
    • *Necphro & Ototoxicity
    • *Photosensitivity
    • *Monitor peak/trough levels
    • --Peat 30 min; 4-10 mcg/mL
    • --Trough; 1-2 mcg/mL
  37. Tetracyclines: doxycycline (Vibramycin)
    • Action
    • *Mostly bacteriostatic effect
    • --Inhibits growth by preventing protein synthesis
    • *Broad spectrum
    • --Gram (+) & gram (-); Mycoplasma pneumoniae, chlamydiae, H. pylori, acne vulgaris
    • *Bacterial resistance has resulted from chronic use
    • --Pneumococcal & gonococcal infections

    • Uses (PO/IM/IV)
    • *Acne
    • *PUD; H. Pylori
    • *Respiratory infections
    • *Rocky Mountain spotted fever
    • *PID; chlamydia

    • Contraindications
    • *Most meds should not be admin w/ renal disease

    • Precautions
    • *Children <8 yrs old - causes teeth discoloration
    • *Pregnancy

    • Med/Food interactions
    • *Milk & antacid products - inhibits drug absorption
    • *Oral contraceptives
    • *Digoxin - Raises level

    • Nursing Considerations
    • *Nephro, Hepato & CNS toxicity
    • *May cause stomatitis
    • *May cause blood dyscrasia
    • *Monitor/educate regarding photosensitivity
    • *May cause GI upset
  38. Fluoroquinolones: Ciproflacin (Cipro/Levoquin)
    • Action
    • *Bactericidal
    • --Interferes with enzyme DNA gyrase
    • *Broad spectrum
    • *Gram +: Streptococcus pneumoniae & Gram -: H. Influenzae, P. aueruginosa, Salmonella, Shigella

    • Uses (PO/IV)
    • *Bronchitis/pneumonia; often first-line drug of choice
    • *UTI
    • *Bone & joint infections
    • *Gonorrhea

    • Contraindications
    • *Pregnancy & breastfeeding
    • *Severe renal disease

    • Precautions
    • *Pediatrics - use only when alternate therapy cannot be
    • *Renal impairment

    • Med/Food Interactions
    • *Antacids decrease absorption
    • *Can inc. theophylline, warfarin, & caffeine effects
    • *Levofloxacin can increase effect of oral hypoglycemics

    • Nursing Considerations
    • *GI upset
    • *Monitor for severe GI distress - Pseudo, colitis
    • *Photosensitivity
    • *Hematuria
    • *Crystalluria: increase fluid intake >21/day
    • *infuse IV over 60-90 min
    • *Avoid caffeine
  39. Antifungals: amthotericin B (Fungizone)
    Main one given in ICU

    • Fungal Infections
    • *Superficial infections (mild) - skin, mucous membranes
    • *Systemic infections (severe) - lungs, CNS
    • *Opportunistic infections - candidiasis

    • Antifungal drug groups
    • *Polyenes - amphotericin B (Fungizone), nystatin (Mycostatin)
    • *Azoles - fluconazole (Diflucan), miconazole (Monistat)
    • *Antimetabolic - flucytosine (Ancobon)
    • *Antiprotozoals - atovaquone (Mepron)
    • *Echinocandins - caspofungin (Cancidas)

    • Contraindications
    • *Renal failure

    • Precautions
    • *Renal impairment

    • Med/Food Interactions
    • *Nephrotoxicity increases w/ aminoglycoside use
    • *Antifungal Diflucan can cause increased effect of oral hypoglycemic agents

    • Nursing Considerations
    • *Nephro & Hepatotoxicity
    • *R/F Thrombophlebitis
    • *R/F hypokalemia
    • *R/F bone marrow suppression
    • *GI upset
    • *Monitor for severe GI distress
    • *Administer IV over 2-6 hours
    • *Monitor V/S q 30 min
    • *Hypotension; increase fluids
    • *May administer prophylaxis for infusion reaction
  40. Antitubercular drugs: isoniazid (INH)
    • Action
    • *Inhibits growth of mycobacteria by preventing synthesis of mycolic acid in the cell wall

    • Uses
    • *Active: Multi-drug therapy at least 6 months - 2 phases
    • --Decreases bacterial resistance & treatment duration
    • --First line drugs
    • ----Isoniazid, rifampin, ethambutol, streptomycin
    • ----More effective & less toxic than second-line
    • --Second line drugs
    • ----Capreomycin, cycloserine, ethionamine, kanamycin, amikacin, ciprofoxacin, pyrazinamide
    • ----Less effective; more toxic

    • Contraindications
    • *Liver disease

    • Precautions
    • *Liver impairment

    • Med/Food Interactions
    • *Interferes w/ absorption of Dilantin - toxicity
    • *ETOH increases R/F hepatotoxicity

    • Nursing Considerations
    • *Take INH on empty stomach, 1 hr before meals or 2 hrs after meals
    • *Must follow complete regimen
    • *Collect sputum specimen in early morning
    • *Peripheral neuropathy
    • --Take pyridoxine (vitamin B6) prophylactically
    • --Report numbness, tingling, burning
    • *Photosensitivity
  41. Digitalis toxicity (Digoxin) (Lanoxin)
    • Function
    • *Increases force of cardiac contraction, CO, tissue perfusion
    • *Decreases ventricular rate

    • Considerations
    • *Apical pulse must be >60
    • *Therapeutic level: 0.5-2.0 ng/ml
    • *1/2 life: 36 hrs
    • Maintenance dose: 0.125 - 0.5 mg/dL daily

    • Toxicity
    • Bradycardia, heart block, anorexia, N/V/D, PVC's, dysrhythmias, malaise, blurred vision/illusions (halos), confusion, delerium, death, pastey white skin color

    • Interactions
    • *Diuretics - hypokalemia - increased cardiac uptake of digoxin - toxicity
    • *Tetracycline - increases toxicity
    • *Antacids affect absorption - toxicity
  42. Antihypertensive: Sympatholytics - Beta-Adernergic Blockers (beta blockers)
    • *Antihypertensive drug, used alone or in combo with diuretic
    • --More effective in clients with elevated serum renin level
    • --AA do not respond well, unless used with a diuretic
    • *Also used as anti-angival & antidysrhythimic
    • *Blocks SNS response on myocardial b-adrenergic receptors
    • *Reduces CO; Reduces renin release/HR/Contractility
    • S/E: decreased BP/HR, AV block, depression, lethargy, GI disturbance, bronchospasm/constriction (adverse-hypotension)
    • *Considerations: Do not stop abruptly - rebound HTN, angina, MI, dysrhythmias. Not effective for AA individuals. Do not administer nonselective in asthmatic or heart failure patients.
    • Drug examples: Ends in OLOL
  43. Antihypertensives: Angiotensin-Converting (ACE) Inhibitors
    Doesn't affect cardiac output
    • *Used primarily to treat HTN
    • *Some agents are effective in treating heart failure
    • *Blocks the production of angiotensin II
    • --Decrease peripheral vascular resistance / vasodilation & Na/H2O excretion
    • --Has very minimal affect on CO, rate, or contractility
    • *S/E: Constant / irritating cough, GI distress, H/A, dizziness, orthostatic hypotension, hyperkalemia, tachycardia, first-dose hypotension - especially when used with a diuretic
    • *Considerations: Do not take with potassium sparing diuretics. Not effective for elderly & AA individuals, unless used wiht a diuretic. Do not administer during pregnancy 2' reduced placental flow
    • *Drug Examples: Ends in aPRIL
  44. Antihypertensives: Angiotensin II Receptor Blockers (ARBs)
    • *Antihypertensive agents
    • *Similar to ACE inhibitors
    • --Prevent end release of aldosterone
    • --Acts on the RAAS
    • *Differences:
    • --ARBs block angiotensin II from the ATI receptors
    • ----ACE inhibitors inhibit angiotensin converting enzyme in forming angiotensin II
    • --ARBs do not cause the constant / irritating cough
    • --ARBs affect CO - cause vasodilation & decrease peripheral resistance
    • --May take 3-6 weeks to observe effects
    • *Drug examples: Ends with SARTAN
  45. Antihypertensives: Calcium Channel Blockers
    Found in heart & smooth muscle
    • *Antihypertensive agents
    • *Verapamil (Calan) - used for chronic HTN, angina pectoris, & cardiac dysrhythmias
    • *Reduces BP
    • --Blocks calcium channels - vasodilation, decreased contractility, decreased conduction, & decreased O2 demands
    • *S/E: Decreased BP/HR/AV block, flushing, H/A, dizziness, constipation, nausea, peripheral edema
    • *Considerations: nifedipine / verapamil are potent Ca channel blockers
    • *Severe hypotension & even cardiac death in high doses
    • *Drug examples: Very Nice And Needed Drugs verapamil (Calan), nifedipine (Procardia), amlodipine (Norvasc), nicardipine (Cardene), diltiazem (Cardizem)
  46. Antihypertensives: Nursing Considerations & teachings
    • *Do not self-adjust med; take even if feeling well (unless HR <60)
    • *Abrupt W/D - rebound HTN
    • *Meds are for control of BP, not cure
    • *Addressing modifiable risk factors can help improve health status & BP
    • *Change positions slowly & check BP regularly
  47. Diretics: Thiazides
    • Function:
    • *Acts on distal convoluted renal tuble, beyond the loop of Henle; blocks sodium, chloride, & H2O reabsorption promoting excretion

    • Indication:
    • *HTN & edema; primarily for clients with normal renal function
    • *Not effective for immediate diuresis

    • S/E:
    • *Dizziness, orthostatic hypotension, H/A, N/V, constipation, urticaria (rare), blood dyscrasias (rare)
    • *Serum chemistry abnormalities
    • --Hypo-kalemia, -natremia, -magnesmia, -chloremia
    • --Hyper-calcemia, -uricemia, -glycemia, -lipidemia

    • Considerations:
    • *Do not use with renal disorders, hypokalemia can enhance digitalis - toxicity

    Drug example: hydrochlorothiazide (HCTZ)
  48. Diuretics: Loop (High Ceiling)
    • Function:
    • *Acts on the ascending loop of Henle; Blocks reabsorption of sodium & chloride - sodium & water loss

    • Indication:
    • *Primarily for congestion / edema; 2-3x more effective than Thiazides
    • *Provides immediate diuresis
    • *Less effective as antihypertensive agents

    • S/E:
    • *F&E imbalances, dizziness, orthostatic hypotension, m. alkalosis
    • *Serum chemistry abnormalities
    • --Hypo-kalemia, -natremia, -magnesmia, -calcemia, -chloremia
    • --Hyper-uricemia, -glycemia, -lipidemia
    • --Elevated BUN/Cr
    • --leukocytopenia, thrombocytopenia (rare)

    • Consideration:
    • *Closely monitor K+ levels, I&O's, hypokalemia can enhance digitalis - toxicity, can cause excessive loss, avoid administering at bedtime

    Drug example: furosemide (Lasix), bumetanide (Bumex)
  49. Diuretics: Potassium-sparing
    • Function:
    • *Acts on collecting duct renal tubules & late distal tubules; interferes with the sodium-potassium pump which is controlled by aldosterone
    • *Promotes sodium & water excretion, with potassium retention

    • Indication:
    • *As mild diuretics or in combination wiht another antidiuretic or antihypertensive

    • S/E:
    • *Hyperkalemia, m. acidosis, N/V/D, anorexia, numbness & tingling of hands & feet

    • Considerations:
    • *These drugs are weaker than thiazides & loop diuretics so are typically not used alone. Do not need potassium supplements.

    Drug Examples: spironolactone (Aldactone), amiloride HCL (Midamor)

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