Drug Nutrient Interactions Flashcards
1
Q
Drugs and nutrients can interact by affecting the following:
A
Absorption, Distribution, Metabolism, Excretion
2
Q
What is absorption?
A
transportation of the unmetabolized drug from the site of administration to the body’s circulation (Ex. bisphosphonate)
3
Q
Absorption requires movement of medication from _ to _
A
GI tract, general circulation
4
Q
(T/F) All of a drug dose is absorbed
A
False
5
Q
(T/F) All drug reaches systemic circulation as active drug
A
False
6
Q
What is bioavalibility?
A
the rate and extent to which that drug is absorbed
7
Q
What is the rate limiting step for most solid dose forms from being absorbed?
A
Disintegration and Dissolution
8
Q
What is the rate limiting step for liquid medications being absorbed?
A
Blood perfusion of the intestines
9
Q
What can decrease blood perfusion of the intestines?
A
Disease states, Edema, Surgery, Sepsis
10
Q
What factors can alter medication absorption?
A
1. Drug drug interaction 2 Gastric emptying rate 3. ROA 4. Location of the distal top of the enteral tube 5. Presence of food 6. Formulation of medication
11
Q
How can we enhance absorption?
A
- Use liquid medications to bypass the dissolution step
- Administer liquid medications or pulverized tablets with adequate fluid
- Administer additional free water flushes in conjunction with scheduled medication
12
Q
What factors can inhibit absorption?
A
- Placement of distal tip of enteral tube
- Medications taken on a empty stomach
- GI intolerances during tube feedings (N/V/D, cramping, increased gastric residuals)
- Review medication profile for causes
- Medications that decrease gastric transit time (prokinetic agents)
- Medications delaying gastric emptying/decrease GI motility
13
Q
What medications must be taken on an empty stomach for better absorption?
A
Penicillins, Tetracycline, Rifampin, Levothyroxine
14
Q
How should Penicillins, Tetracyclines, Rifampin, and Levothyroxine be administered?
A
- Hold feeds 30-60 min before medication administration
- Hold feeds 30 minutes after medication administration
- Readjust feeding schedule to ensure patient receives 24 hr nutritional needs
15
Q
What drugs decrease gastric transit time (prokinetic agents)?
A
- Metoclopramide
- Erythromycin
16
Q
What drugs delay gastric emptying/decrease GI motility?
A
- Anticholinergics
- Aluminum containing antacids
- Narcotics
17
Q
How does protein binding affect distribution?
A
- May increase half life of drug
- Decrease hepatic metabolism
18
Q
How does solubility affect tissue distribution?
A
- Hydrophilic substances are distributed in fluid compartments of the body (vise versa)
19
Q
What enzyme system is primarily used in metabolism?
A
Cytochrome P450 enzyme system
20
Q
What Cytochrome P450 enzyme is involved in metabolism of most currently marketed drugs?
A
***CYP3A4*** Others: - CYP1A2 - CYP2C9 - CYP2D6
21
Q
What food induces CYP1A2?
A
- Broccoli
- Brussels sprouts
- Charcoal-broiled meats
22
Q
What drugs are metabolized by CYP1A2?
A
- Check other sheet
23
Q
What Cytochrome P450 enzyme is inhibited by grapefruit juice?
A
- CYP1A2
- CYP3A4
24
Q
What Cytochrome P450 enzyme is inhibited by cranberry juice?
A
- CYP2C9 (Warfarin metabolism - results in increased INR and bleeding)
25
What drugs are metabolized by CYP3A4?
* Check other sheet
26
What is the major elimination pathway for most water-soluble drugs and metabolites?
Urinary (renal)
27
Alterations in _ function have profound effects on drug clearance
Urinary (renal)
28
What drugs undergo enterhepatic cycling?
Macrolides, ceftriazone, nafcillin, doxycycline, amiodarone
29
How does gastrointestinal (bile) excretion work?
Drugs enter duodenum via common bile duct
30
What are the 5 types of enteral incompatibilities?
physical, pharmaceutical, physiologic, pharmacologic, pharmacokinetic
31
What is physical incompatibility?
Chemical instability that occurs when two susceptible substances are mixed together and results in a physical change between two substances
32
What types of physical incompatibilities can occur?
- Precipitate formation: curdling, flocculation (flaking), altered enteral formation consistency, viscosity
33
What is pharmaceutical incompatibility?
Alteration in the drug form itself that interferes with efficacy, potency, and tolerance
34
What medications in specialized dosage forms cannot be used in feeding tube administration?
- Enteric coated (cannot crush)
- Extended release
- Sustained release
- Sublingual
35
What is physiologic incompatibility?
result from nonpharmacologic action incurred by the medication or by the suspending medium
36
What does physiologic incompatibility typically occur with?
- High osmolality liquid medications
| - Sorbitol containing medications
37
Patients with a physiologic incompatibility typically experience:
nausea, bloating, increased gastric residuals, cramping, diarrhea
38
What is pharmacologic incompatibility?
Results when a medication alters tolerance of the EN or PN regimen because of its mechanism of action
39
What typically occurs from a pharmacologic incompatibility?
- Leads to greater than expected pharmacologic effect of medication (ex. prokinetic agent)
- Lead to unintended side effects of medication (ex. Narcotic analgesics)
40
What is pharmacokinetic incompatibility?
EN or PN regimen alters the bioavalibility, absorption, distribution, metabolism, and/or elimination of a medication
41
What common medications cause pharmacokinetic incompatibility?
phenytoin, warfarin, ciprofloxacin, meds that should be taken on empty stomach (levothyroxine)
42
What medications can be administered via enteral feeding tubes? and how?
- IR forms: Oral tabs, Hard gelatin capsules, Soft gelatin capsules, Liquid formulations
- Mix with appropriate diluent and administer separately.
- Flush feeding tube with water befoer and after each medication is administered
43
How are IR tablets administered via enteral feeding tubes?
- Crushed to a fine powder
| - Mix with water before administration
44
How are IR hard gelatin capsules administered via enteral feeding tubes?
- Open and mix thoroughly with water
45
How are IR soft gelatin capsules administered via enteral feeding tubes?
- Empty by creating a pin-hole in one end of capsule
| - Squeeze contents out and mix with water
46
What is the preferred alternative for administration via enteral tubes? Why?
Liquid medications
- Better absorption
- Decreased potential for enteral tube occlusion
- Potential for producing adverse effects
47
What are physiologic incompatibilities pertaining to liquid medications?
- Sorbitol containing (present in all liquids except tinctures and emulsions)
- Hyperosmolar liquid (stomach more tolerant, dilute with appropriate amounts of water
48
What physiologic incompatibility pertains to suspensions?
- Few incompatibility concerns!
| - Can be hyperosmolar
49
What are granular type medications?
- Psyllium hydrophilic mucilloid
| - Cholestyramine resin
50
What is Cholestyramine resin used for?
- To control diarrhea
| - Added as hypercholesterolemia agent
51
How should granular-type medications be prepared before administration?
- Requires dilution with water
| - Forms gelatinous mixture that can occlude feeding tube (do not use with small bore feeding tubes)
52
What dosage forms are not recommended for administration via tube?
- Enteric coated medications
- Sublingual/buccal medications
- Sustained release/ER
- Syrups
53
What is the purpose of enteric coating?
- Protect stomach lining
| - Protect from destruction in acidic environment
54
Why is enteric coated medications not recommended for administration via tube?
- May induce pharmaceutical incompatibility
| - Therapeutic equivalent or alternative administrative should be considered
55
Why is sublingual/buccal medications not recommended for administration via tube?
- Placed under tongue or cheek pouch for administration (absorbed into systemic circulation)
56
Why is sustained release/ER medications not recommended for administration via tube?
- high peaks/low troughs
- capsules containing beads can lead to occlusion of tube
- dissolving in water or saline can affect integrity of beads
57
Why are syrups not recommended for administration via tube?
- Physical incompatibility
- Denatures protein in EN at pH less than or equal to 4
- Be aware of protein source of EN (free AA and hydrolyzed formulations or not as affected)
- Physical incompatibilities cannot be avoided by diluting the syrup
58
How do capsule PPIs containing enteric-coated beads need to be prepared?
- Mix with acidic juice (apple or orange)
| - Dissolve beads in 8.4% sodium bicarbonate solution
59
How do enteric coated PPI tablets need to be prepared?
- Dissolve beads in 4.2% sodium bicarbonate solute
60
Phenytoin can have a pharmacokinetic incompatibility (impaired absorption) with _
protein; its highly protein bound
- may need higher doses than usual
- seizure are a consequence of low blood concentrations
61
Strategies to Maintain therapeutic phenytoin levels
- Hold tube feeding 2 hours before and 2 hours after phenytoin dose
- Dilute phenytoin with 30-60 mL of water before administration
- Monitor blood levels more frequently when changing from established parenteral dose to suspension form
62
What does warfarin do to patients receiving tube feeding?
- Decreased therapeutic dose
- Highly protein bound
- Consider bolus or cyclic feeding
63
Compatibility of PN infused with other additives influenced by:
- Exposure time b/w nutrients
| - Additives present
64
What is a great reference for PN compatibility?
Trissel's handbook on injectable drugs
65
What two drugs are safe to add to PN?
Insulin and famotidine
66
(T/F) Admixing PN with medications is not advised
True
67
(T/F) We can use Y-site administration of medications in PN
False; PN should be administered via a dedicated line at all times
