Drug Incompatibilities

Question 1

What is phenytoin used for?

Answer 1

The management of generalized tonic-clonic seizures, simple or complex partial seizures, and status epileptics as well as for the treatment or prevention of seizures during or following trauma or neurosurgery

Question 2

Phenytoin is available as a a variety of dosage forms for what types of administration ?

Answer 2

oral and IV admin

Question 3

The product monograph for the IV dose form which contains ____mg/mL warns that administration must not exceed 50mg/minute bc of the risk of severe hypotension and cardiac arrhythmias

Answer 3

50

Question 4

What is the recommended loading dose that the manufacturer recommends for phenytoin?

Answer 4

10-15 mg/kg by slow IV administration (at a rate not exceeding 50mg/min)

Alternatively, generally accepted guidelines suggest 15-20 mg/kg by slow IV administration (at a rate not exceeding 50mg/min)

Question 5

What is the recommended maintenance rate that the manufacturer recommends for phenytoin?

Answer 5

100mg IV every 6-8 hours not to exceed 50 mg/minute

Question 6

What should the rate of phenytoin be for elderly patients and those with CV disease?

Answer 6

Rate of admin should not exceed 25 mg/min

Question 7

For elderly and those with CV disease:

Since the product comes as a 50 mg/mL solution, there often is a need to further _______ the product

Answer 7

dilute

Question 8

Phenytoin sodium injection USP (50mg/mL) contains phenytoin at a concentration that exceeds its _____ solubility

Answer 8

aqueous

Question 9

What is the water solubility of phenytoin?

Answer 9

0.035 mg/mL

Question 10

What co solvents are added to phenytoin?

Answer 10

alcohol 10%

propylene glycol 40%

Question 11

Because phenytoin is an extremely ____ _____, the pH is adjusted to 12

Answer 11

weak acid

Question 12

Primary

Answer 12

Use undiluted drug and administer by slow intravenous injection at a rate not exceeding 50 mg per minute

Question 13

Package insert

Answer 13

The addition of phenytoin solution to intravenous infusion is not recommended due to lack of solubility and resultant precipitation

Question 14

Secondary

Answer 14

Extemporaneous preparation: 0-100 mg in 50 mL normal saline (NS) given over 5-15 mins. The product must be used within 2 hours and use of an in-line filter is recommended.

Question 15

What was the purpose of this lab?

Answer 15

To observe the physical incompatibility of phenytoin during dilution, each student pair will dilute the injection into different concentrations and record the results after standing for 2 days.

Question 16

Describe the process of activities that we did in this lab

Answer 16

• Using a 1 mL syringe, 0.5 mL of normal saline will be added to each of the 5 labeled tubes.
• 0.5 mL of phenytoin will be added to Tube #1, the contents mixed and then 0.5 mL withdrawn and added to Tube #2 (SERIAL DILUTIONS)
• This process is repeated up to Tube #5 which will contain 1 mL in the end.
• This process is repeated using 5% dextrose in water (D5W)
• The tubes will be sealed with parafilm and left at the back of the bench until the following lab session when the results should be recorded, the solutions dumped into the appropriate waste container and the empty tubes placed int he broken glass receptacle

Question 17

Explain how the results should have been.

Answer 17

Should have had precipitation in all of them ?
But for sure as concentration decreased, there should have been precipitate.

The more you dilute it, the less cosolvent was present so a precipitate formed.

Question 18

Why was alcohol added?

Answer 18

Used as a preservative to prevent bacterial growth

Question 19

Why was propylene glycol added?

Answer 19

Used as a surfactant to increase the solubility of the solute in the solvent\

Question 20

List examples of aminoglycosides

Answer 20

• gentamycin
• tobramycin
• metilmicin
• amikacin

Question 21

How do aminoglycosides work?

Answer 21

Work by binding to the bacterial 30S ribosomal subunit, causing misreading of t-RNA, leaving the bacterium unable to synthesize proteins vital to its growth.

Question 22

What are aminoglycosides good at targeting ?

Answer 22

Aminoglycosides are useful primarily in treatment of infections involving aerobic, GN bacteria

Question 23

How are aminoglycosides administered?

Answer 23

IV, in doses based on body weight

Question 24

What are potential toxicities with aminoglycosides and how are they monitored?

Answer 24

Ototoxicity and renal toxicity

-blood drug levels and creatinine are monitored

Question 25

What is included in B-lactam antibiotics ?

Answer 25

• penicillin derivatives
• cephalosporins
• monobactams
• carbapenems
• B lactase inhibitors

Question 26

What are B-lactam antibiotics indicated for?

Answer 26

bacterial infections caused by GP bacteria

Question 27

Some broad spectrum B-lactams are also active against various ______ ______ organisms

Answer 27

gram negative

Question 28

How do B-lactam antibiotics work?

Answer 28

B-lactam antibiotics act by inhibiting synthesis of peptidoglycan layer of bacterial cell walls, subsequently leading to cell wall structural disintegration

Question 29

When would you use combo of aminoglycosides and B-lactams?

Answer 29

in several very severe infections

ex. sub-acute bacterial endocarditis, the causative organism is frequently resistant to many antibiotics

Question 30

In the case of sub-acute bacterial endocarditis, what is the bug?

Answer 30

often a group D streptococcus that is only moderately sensitive to aminoglycisdes and B-lactam groups.

Question 31

What happens when you add aminoglycosides and B-lactams together?

Answer 31

SYNERGY

-causing the streptococcus to be very sensitive to the combination of these medications

Question 32

Since both ahminoglycosides and B lactic antibiotics are administered concurrently sometimes, there is a desire to administer them as an admixture. In this exercise, some of the drug combinations will be tested for ________ problems

Answer 32

incompatibility

Question 33

Explain the procedure of this lab (aminoglycoside + B-lactam)

Answer 33

-Gently mix 1 mL of the drug with 1 mL of amino glycoside solution, using disposable needle/syringe and test tube, and observe the results. Each student group will be assigned to one of the drug combinations and the class results will be tabulated for further discussion.

Question 34

While it might not be necessary to mix all medications under therapeutic situations, there are possibilities when certain medications will be added together for _______ of treatment regimens.

Answer 34

convenience

Question 35

Describe the incompatibilities - commercial products lab

Answer 35

• Mix 0.5 mL of each component in combination as shown in the table, using disposable needle/syringe and test tubes.
• Observe the tubes approximately 15 minutes after mixing and record your results.

Question 36

If a solution remains clear after mixing, is it reasonable to assume that no interaction has occurred?

Answer 36

No, not all reactions are visible so just because a solution remains clear after mixing doesn’t mean a reaction didn’t happen.

If no reaction is visible it doesn’t automatically mean they are compatible.