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Pharm407 > Lecture 7 part 2: pharmaceutical aspects of CVD2 > Flashcards

Lecture 7 part 2: pharmaceutical aspects of CVD2 Flashcards

1
Q

What are nasogastric tubes? (3 points)

A
  • Tubes which run from the outside of the body into the nose, down the oesophagus and to the stomach.
  • they are 24-36 inches in length
  • used to administer nutrients, liquids and drugs for a patient unable to swallow (e.g. after a stroke)
  • made from polyvinyl chloride with plasticizers (e.g. DEHP) to make it more flexible
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2
Q

What are some examples of medications a post-infarct stroke patient expected to be on? (3 points)

A
  • statins
  • hypoglycaemic agents
  • anticoagulants
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3
Q

What questions must be considered regarding medication for stroke patients? (3 points)

A
  • can drugs be crushed
  • can drugs be administered with food
  • can drugs be administered with liquids
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4
Q

Why is there a need for off-license use of medications in stroke patients? (1 point)

A

-there are no commercially available liquid medications formulated for tube administration.

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5
Q

What are the considerations of giving warfarin via a NG tube? (2 points)

A
  • warfarin may bind to food proteins, therefore may require to withold food
  • Warfrin bindsto plastics and there is an increased binding at lower pH
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6
Q

Is warfarin better administered with food? (3 points)

A
  • Yes it is better to administer warfarin with the food.
  • Although the onset will be later, after a certain period of time it will be absorbed
  • If you just give it as an oral suspension it will bind to the surface of the tube and not be absorbed
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7
Q

What difficulties arise from administering CR tablets via a NG tube? (3 points)

A
  • Tablets going through a NG tube will need to be crushed
  • Crushing a CR tablet bascially destroys the actual property of the formulation thus will release the drug in an extremely high concentration
  • Some polymers may swell in the water and block the NG tube
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8
Q

What happens if you cannot find a conventional release formulation of a medicine to administer via a NG tube? (2 points)

A
  • re calculate the dose if a CR tablet has to be crushed

- be aware that the patient will experience all the side effects

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9
Q

What are the two salts metoprolol is available as in NZ?

A
  • tartate

- succinate

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10
Q

How is CR achieved in beataloc? (3 points)

A
  • the active ingredient is incorporated in coated beads in a disintegrating tablet
  • the tablet rapidly disintegrates and hundreds of beads are dispersed in GI fluid
  • The active compound is released over 20 hours (depends on GI transit times)
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11
Q

How is CR achieved in metoprolol CR?

A

-contains polymer coated beads of metoprolol

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12
Q

can metoprolol succinate beads be crushed?

A

-no but they can be divided

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13
Q

What are the brands of metoprolol succinate ?

A

betaloc CR and metoprolol AFT CR

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14
Q

What are the brands of metoprolol tartrate?

A

Lopresor (immediate release)

Slow-Lopresor

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15
Q

Can you crush lopressor?

A

yes

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16
Q

What will you suggest for a patient requiring metoprolol who was stable on betaloc CR 95mg od but now has a NG tube placed due to swallowing difficulties? (2 points)

A
  • beataloc is a metoprolol succinate form of the drug

- lopressor (metoprolol tartrate) 50mg can be given bd as these can be crushed.

17
Q

What is digoxin? (7 points)

A
  • Drug with a very narrow therapeutic range (1-2ug/mL)
  • highly potent drug which needs to be customised to individual
  • Widely distributed in the body and excreted renally
  • available as tablets and elixirs
  • extensively tissue bound
  • terminal half life ~30-40 hours, extended with renal impairment
  • Loading dose required, maintenance dose based on elimination rates.
18
Q

What individual functions is digoxin dosing based on? (3 points)

A
  • age
  • lean body weight
  • renal function
19
Q

How does the bioavailability of digoxin elixir compare to the tablet? (2 points)

A
  • tablet = 63%

- elixir = 75%

20
Q

What makes plasticizers in the NG tube interact with substances administered by it? (4 points)

A
  • NG tube is made from polycinylchloride combined with 2-di-ethyl-hexyl-pthalate to make it more flexible
  • the extent of DEHP relase from the PVC is a functional of lipophilicity
  • foods with high lipid content may cause the DEHP to leak out and interact with drug
  • Normally it leaks out in trace amounts, but if you are using lipids a lot it might solubilise the plasticizer
21
Q

What is the relationship between digoxin and food?

A

-food slows the rate of absorption of digoxin, but does not affect the total amount of digoxin absorbed

22
Q

What are symptoms of digoxin toxicity? (4 points)

A
  • nausea & vomiting
  • loss of appetite
  • confusion
  • blurred vision
23
Q

How is digoxin monitored?

A

-blood levels are taken >6 hours after the last dose

24
Q

What is a heparin? (3 points)

A
  • highly sulfated glycosaminoglycan
  • has the highest negative charge density of any known biological molecule
  • cannot cross intestinal epithelium
25
Q

Why can’t heparin cross the intestinal epithelium? (3 points)

A
  • passive diffusion across the intestinal epithelium is restricted to small lipophilic molecules
  • there is an ionic repulsion between heparin and biological membranes as both are negatively charged
  • both UH and LMWH must be administered parenterally
26
Q

What is an example of unfractionated heparin? (6 points)

A
  • multiparin (heparin sodium 5,000 IU/mL) available as solution for injection or solution concentrate for infusion
  • MW ~15kDa
  • requires loading dose followed by continuous infusion
  • anticoagulant response is unpredictable (APTT monitoring required)
  • metabolised in liver, inactive metabolites are excreted renally
  • incompatible with many injectables
27
Q

how is UH given with? (4 points)

A
  • continuous IV infusion in 5% glucose or 0.9%NaCl
  • intermittent IV injection
  • SC injection
  • due to its short half life, infusion or SC injection is preferred over intermittent IV injection
28
Q

What is the difference between UF and LMWH? (3 points)

A
  • UH means that it contains variable chain length and molecular weight
  • The anticoagulant effect depends on molecular weight and size, therefore the PK ad effect is not as predictable for heparin
  • LMWH are fractionated therefore contains known molecular sizes/weights, therefore the PK and effects are more predictable
29
Q

What is LMWH- enoxaparin? (8 points)

A
  • equally as effective as UH
  • more convenient to use with od or bd SC dosing
  • more favourable side effects
  • predictable response
  • low interpatient variation
  • half life = 4 hour (single dose) or 7-12hours (after repeated dosing)
  • available in prefilled syringes, prefilled graduate syringes and ampoules
  • renally excreted
30
Q

What are the advantages of a predictable response with LMWH? (3 points)

A
  • allows for fixed-weight adjustment of SC dose
  • most patients don’t require lab monitoring
  • out patient treatment is possible
31
Q

What are the advantages of SC administration of LMWH? (2 points)

A
  • bioavailability more or less 100%

- unlike UH, there is linear absorption with LMWH

32
Q

Why are the different LMWH products not bioequivalent? (2 points)

A
  • differences in MW

- differences in specific anti-Xa activities

33
Q

When should the LMWH dose be reduced? (2 points)

A
  • if the patient’s CrCl<30mL/min

- could also change to UH

34
Q

What is SNAC? (4 points)

A

sodium N-(8-(2-hydroxybenzoyl)amino)caprylate (SNAC)

  • small carrier molecule (200-400Da) which enables heparin to be absorbed from the GIT
  • weak non-covalent interaction between SNAC and heparin
  • hydrophobic moieties of SNAC drug carrier complex is created with increased lipophilicity which enhances epithelial membrane permeability
  • drug/carrier interaction is reversible and dissociation occurs in the blood due to dilution effects
35
Q

What are the pharmacokinetics of amiodarone oral tablets? (4 points)

A
  • oral bioavailability 22-86% incompletely and eratically absorbed with extensive intersubject variation
  • Half life ~25 days (14-110 days)
  • aim for lowest effective concentrations due to unpredictability
  • extensively distributed into tissues including adipose tissue
36
Q

What are the loading and maintenace doses for amiodarone oral tablets? (2 points)

A
  • loading dose 200mg tds for 1 week followed by 200mg bd for 1 week
  • maintenance dose: 200mg or less, od
37
Q

What are the PK of amiodarone IV injections? (7 points)

A
  • 150mg available in each 3mL ampoule
  • given as 5mg/kg infusion over 20min-2 hour
  • administered in 250mL of 5% glucose
  • incompatible with saline
  • do not mix with other preparations
  • interacts with PVC infusion bags, administration sets and interacts with plasticizers
  • may reduce drop size
38
Q

How does amiodarone interact the PVC infusion bags, administration sets etc? (3 points)

A
  • absorbs onto PVC infusion bags and administration sets
  • thought to be due to plasticizers
  • Amiodarone containing solutions may cause plasticizer DEHP to leach out of plastics
39
Q

What can be done to reduce amiodarone interactions with the administration equipment? (3 points)

A
  • prepare infusion immediately prior to use
  • use glass or rigid PVC bottles
  • use non-DEHP containing equipment

Pharm407 (5 decks)

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