Pharm/Pain Flashcards
What is volume of distribution?
Theoretical volume in the body (fluids and tissues) in which the drug may be found after absorption
What is the concentration of the drug equal to?
Amount administered (dose)/The volume of distribution (Vd)
What is clearance?
Fraction of the drug that is cleared from the body in any given unit of time
Why is clearance important
Dictates how much of drug must be given and how often to maintain desired concentration in the body
What is bioavailability?
Amount of administered drug that actually reaches the blood
What 2 classes of drug decrease the bioavailability of calcium, magnesium, iron, and aluminum compounds?
Cephalosporins and Fluoroquinolones
If a drug is given IV, what is the bioavailability?
100%
If a drug is given PO, sublingual, PR, IM, SQ, ect… what 2 things determine its bioavailability?
- Host factors: Diet, illness, organ function
2. Drug factors: Whole, crushed, solution, injected
What are 2 reasons a drug concentraiton might be low?
- Bioavailability is low
2. Clearance is high
What is a lipophilic agent?
Bioavailability is enhanced by fatty foods
Name 2 drugs that are lopophilic and should be taken with fatty foods
- Istretinoin
2. Griseofulvin
What is half life?
The amount of time required for the concentration of the drug to decrease by half
After 1 half life, how much of the drug remains?
50%
After 2 half life, how much of the drug remains?
25%
After 3 half life, how much of the drug remains?
12.5%
After 4 half life, how much of the drug remains?
6.25%
After 5 half life, how much of the drug remains?
3.125%
After how many half-lives is approximately 97% of a drug cleared from the body?
5
What is steady state?
When a drug is administered at a constant interval and accumulates in the body so the amount in equals the amount out
Drug accumulation follows the same pattern as what?
Half-life clearance
After 5 half lives a drug reaches what % of steady state?
97%
When a dose or dosing interval changes, how many half lives are required to reach a new steady state?
5
What is absorption?
The progression of the drug from site of administration to the target sites
Name 3 reasons drugs administered PO are different in kids than adults
- Neonates and young infants have elevated gastric pH
- Neonates and young infants have delayed gastric emptying
- Proteins that are required for conversion from a pro-drug to a drug, and for drug transport, are expressed differently at different ages
What are some things which can change absorption or concentration of a drug?
- Crushing tabs into suspension
- Flavoring
- Mixing into formula or juice
What is distribution?
Where the drug disperses after it is absorbed into systemic circulation
What are two things that cause different distribution of drugs in kids (depending on whether they are hydrophilic or lipophilic)?
- Higher percentage of total body water
2. Lower body fat stores
What are 3 things which can affect the distribution of drugs?
- Serum levels of albumin
- Serum levels of other binding proteins
- Transporters
What is the primary organ for drug metabolism?
Liver
Name other organs which have drug-metabolizing enzymes besides the liver
Skin, kidney, GI tract, lungs
What are 3 drugs you can’t have dairy with because they are chelated by dairy products?
- Tetracycline
- Doxycycline
- Ciprofloxacin
What happens if you take an antiacid with an iron supplement?
It binds to the iron and prevents absorption increasing its elimination in the GI tract
How is phenytoin distributed?
Bound to plasma proteins
What happens if you give sulfa drugs with phenytoin?
Sulfa causes phenytoin to unbind and increases potential toxicity and elimination
What is involved in the first phase of liver metabolism?
CYPs (oxidases)
-Different CYP’s become active at different ages and drug metabolism changes depending on level of each CYP
What are some concomitant drugs/herbal remedies which can affect metabolism of certain drugs?
St. John’s Wort, Ginkgo Biloba, Milk Thistle (Mom may be taking these and transferring via breast milk)
Erythromycin, ciprofloxacin, cimetidine, and omepraxole have what effect on hepatic enzymatic systems?
Inhibitory
Rifampin, phenobarbital, carbamazepine, and phenytoin have what effect on hepatic enzymatic systems?
Inducers
What is the impact of drugs which have an inhibitory effect on hepatic enzymatic systems?
Reduces theophylline, codeine, beta blockers, antidepressants, corticosteroids, warfarin, and metronidazole metabolism-> Increased bioavailability and toxicity
What is the effect of drugs that are inducers of hepatic enzymatic systems?
Causes other drugs metabolized by the same enzyme to be eliminated quicker requiring higher dosing to maintain a desired concentration
What two organs are responsible for most drug excretion?
- Liver (bile)
2. Kidney (urine)
What is excretion dependent on?
The ability of transporters to get the drug from the circulation into the bile or urine for excretion
(If one drug inhibits a transporter, then another drug can’t be transported and will accumulate to toxic levels in body)
What is the functional expression of transporters dependent on?
- Age
- Liver injury/disease
- Kidney injury/disease
What should you consider if they mention liver or kidney disease in a child?
Potential for drug toxicity
Why must levels of drugs be monitored so closely in infants?
Elimination is unpredictable
True or False: Medications that are eliminated by the liver won’t be impacted in a patient with renal disease
True (same vice versa)
What two drugs can inhibit renal metabolism of digoxin resulting in elevated levels?
- Quinidine
2. Amiodarone
Name 3 drugs used for SVT and HTN
- Atenolol
- Metoprolol
- Propranolol
What are 3 systems affected by beta blockers?
- CNS
- Smooth muscle
- Cardiac
Name 7 side effects of beta blockers
- Difficulty sleeping
- Fatigue
- Bronchospasm
- Cold extremities
- Bradycardia
- Heart block
- Sexual dysfunction
What is the most likely explanation in a teenager on meds who has variable effects or unexpected drug levels?
Poor compliance
What condition can beta blockers exacerbate?
Asthma
What type of medication is acetazolamide?
Carbonic anhydrase inhibitor (CAI)
How do carbonic anhydrase inhibitors work?
They prevent the reuptake of bicarbonate in the proximal tubule
What do carbonic anhydrase inhibitors do to the urine?
Alkalinize it
What electrolyte abnormality does carbonic anhydrase inhibitors cause?
Metabolic acidosis
What electrolytes do loop diuretics block the absorption of?
Na and Cl
What electrolytes do loop diuretics result in the wasting of?
Calcium, K, and H
What electrolyte abnormality do loops diuretics result in?
Hypochloremic, hypokalemic, metabolic alkalosis
Name 2 dose-related side effects of furosemide
- Ototoxicity
2. Renal toxicity
Name 2 thiazide diuretics
- Hydrochlorothiazide
2. Metolazone
Which diuretic causes hyponatremia and hypochloremia (Na and Cl are lost at the distal tubule)?
Thiazide
Which diuretic causes contraction alkalosis by causing water loss at the distal tubule?
Thiazide
With thiazide diuretics, the chloride anions that are lost at the distal tubule are replaced by what?
Bicarb
What electrolyte derangement do thiazide diuretics cause?
Metabolic alkalosis
What type of diuretic is mannitol?
Osmotic
How does mannitol work?
Keeps water in the tubules through osmotic pressure resulting in an osmotic diuresis
*Pulls fluid from IC to EC space and blocks fluid reabsorption at kidney level, further decreasing IC fluid levels
What kind of acid/base effect does Mannitol have?
None
What effect does spironolactone have on Na and K?
Na is excreted, K is retained (K sparing)
What acid/base derangement can spironolactone lead to?
Metabolic acidosis
Name 3 negative effects of ASA
- Reye syndrome
- GI irritation (most likely)
- Tinnitus (dose-related)
What was minimal sedation formerly known as?
Anxiolysis
What describes a drug-induced relief of apprehension with minimal effect on perception and sensorium?
Minimal sedation (anxiolysis)
What was moderate sedation formerly known as?
Conscious sedation
What type of sedation is it when the patient retains the ability to respond normally to verbal commands and CV functions are not affected?
Moderate sedation (conscious sedation)
What is patient response in deep sedation?
Responds to repeated or painful stimuli
What happens to the protective airway reflexes in deep sedation?
Partial or complete loss (need assistance with airway protection
What sedation level describes a person who is unarousable with any stimulation and has complete loss of consciousness and airway protective reflexes?
General anesthesia
What must be monitored during general anesthesia?
Vitals
Name 4 things required for conscious sedation
- PALS certified staff member to monitor (no other roles)
- Pulse ox & BP (Vitals every 5 minutes)
- Bag mask & O2
- Reversal agents (naloxone/flumazenil)
True or False: EKG monitoring is required for conscious sedation
False: In absence of underlying cardiac history, EKG monitoring isn’t needed
