Drug Incompatibilities Flashcards
What is phenytoin used for?
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
Phenytoin is available as a a variety of dosage forms for what types of administration ?
oral and IV admin
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
50
What is the recommended loading dose that the manufacturer recommends for phenytoin?
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)
What is the recommended maintenance rate that the manufacturer recommends for phenytoin?
100mg IV every 6-8 hours not to exceed 50 mg/minute
What should the rate of phenytoin be for elderly patients and those with CV disease?
Rate of admin should not exceed 25 mg/min
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
dilute
Phenytoin sodium injection USP (50mg/mL) contains phenytoin at a concentration that exceeds its _____ solubility
aqueous
What is the water solubility of phenytoin?
0.035 mg/mL
What co solvents are added to phenytoin?
alcohol 10%
propylene glycol 40%
Because phenytoin is an extremely ____ _____, the pH is adjusted to 12
weak acid
Primary
Use undiluted drug and administer by slow intravenous injection at a rate not exceeding 50 mg per minute
Package insert
The addition of phenytoin solution to intravenous infusion is not recommended due to lack of solubility and resultant precipitation
Secondary
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.
What was the purpose of this lab?
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.
Describe the process of activities that we did in this lab
- 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
Explain how the results should have been.
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.
Why was alcohol added?
Used as a preservative to prevent bacterial growth
Why was propylene glycol added?
Used as a surfactant to increase the solubility of the solute in the solvent\
List examples of aminoglycosides
- gentamycin
- tobramycin
- metilmicin
- amikacin
How do aminoglycosides work?
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.
What are aminoglycosides good at targeting ?
Aminoglycosides are useful primarily in treatment of infections involving aerobic, GN bacteria
How are aminoglycosides administered?
IV, in doses based on body weight
What are potential toxicities with aminoglycosides and how are they monitored?
Ototoxicity and renal toxicity
-blood drug levels and creatinine are monitored
What is included in B-lactam antibiotics ?
- penicillin derivatives
- cephalosporins
- monobactams
- carbapenems
- B lactase inhibitors
What are B-lactam antibiotics indicated for?
bacterial infections caused by GP bacteria
Some broad spectrum B-lactams are also active against various ______ ______ organisms
gram negative
How do B-lactam antibiotics work?
B-lactam antibiotics act by inhibiting synthesis of peptidoglycan layer of bacterial cell walls, subsequently leading to cell wall structural disintegration
When would you use combo of aminoglycosides and B-lactams?
in several very severe infections
ex. sub-acute bacterial endocarditis, the causative organism is frequently resistant to many antibiotics
In the case of sub-acute bacterial endocarditis, what is the bug?
often a group D streptococcus that is only moderately sensitive to aminoglycisdes and B-lactam groups.
What happens when you add aminoglycosides and B-lactams together?
SYNERGY
-causing the streptococcus to be very sensitive to the combination of these medications
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
incompatibility
Explain the procedure of this lab (aminoglycoside + B-lactam)
-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.
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.
convenience
Describe the incompatibilities - commercial products lab
- 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.
If a solution remains clear after mixing, is it reasonable to assume that no interaction has occurred?
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.
