Exam 4 - Byrn Flashcards
What is important to know about hydrolysis?
It is a major reaction that involves water attacking the molecule.
Molecule will cleave and break into two fragments.
Water often reacts and degrades a drug which is why it is important to not store medicines in a humid environment. EX: aspirin will start to smell like vinegar
What is the relationship between concentration and time (in hrs)
There is an accelerated breakdown of a drug in aqueous solution at elevated temperatures.
When is a solution stable?
At a certain concentration, for a certain time, at a certain temperature, at a certain degree of light exposure.
When is a solid drug stable?
For a certain time, at a certain temperature, at a certain degree of light exposure
When is compactability a problem?
It is a problem for longer infusion times with piperacillin, tazobactam, azithromycin, ciprofloxacin, tobramycin, vancomycin, insulin and some vasopressors.
What are common problems with drugs due to temperature?
High temps speed up chemical reactions and break down drugs and proteins.
Majority of IV drugs are refrigerated for longer stability except furosemide and phenytoin.
There is a handful of IV drugs that can be kept at room temperature such as metronidazole, moxifloxacin acetaminophen, acyclovir, pentamidine and valproate.
What is important to know about light exposure?
Light exposure can cause photodegradation and in some cases, increase formulation toxicity.
Amber vials protect from light.
Vitamin K, nitroprusside, doxycycline must be protected throughout administration.
Important to check drugs for color changes or change in appearance.
What is the definition of stability?
(Shelf life) stability is the extent to which a product retains the same properties and characteristics throughout its period of storage and use.
Certain functional groups are more susceptible to degradation.
What are 3 chemical reactions that cause drug degradation?
Oxidation-reduction
Hydrolysis
Photolysis
How can you prevent oxidation?
Protection from changes in temp.
Control pH with buffers.
Amber bottles to protect from light.
Store in colder temperatures to slow reaction.
Chelating agents (EX: EDTA) remove metal ions that can cause oxidation.
Antioxidants can remove free radicals produced by oxidation
What compounds are likely to be hydrolyzed?
Carbonyl, amide and cyclic groups
Is there a way to prevent hydrolysis?
Remove moisture (no water, hydrolysis can’t take place).
Freeze dry to remove water (lyophilization).
Avoid solids that absorb water (non-hygroscopic compounds).
Control the temperature.
Control the pH.
What are some of the functions of dosage forms?
Provide and accurate dose.
Promote drug dissolution.
Promote delivery to the site of action.
Ensure drug stability.
Control drug delivery in the body.
Determine dosage interval.
What is important to know about ester hydrolysis under basic conditions?
The reaction starts with a nucleophilic attack by the hydroxide anion on the ester carbonyl group.
Resulting in carboxylic acid and alcohol as the products.
What will help prevent the hydrolysis of esters and lactones?
Protection from moisture.
Protection from heat.
Controlling the pH in solution formulations.
What is important to know about the amide hydrolysis under basic conditions?
The reaction starts with a nucleophilic attack by the hydroxide anion on the amide carbonyl group.
Resulting in carboxylic acid and amine as the products.
What will help prevent the hydrolysis of amides and lactams?
Protection from moisture.
Protection from heat.
Controlling the pH in solution formulations.
What is important to know about he auto-oxidation of captopril?
Captopril is an angiotensin converting enzyme (ACE) inhibitor used to treat hypertension and congestive heart failure.
First one created.
Oxidation is caused by metal ions.
What are the most important things to know about oxidation and photolysis?
Oxidation is common, it is complicated route of degradation. May functional groups are subject to oxidation.
Oxidation can be minimized through protection of light, air, metals and addition of excipients.
Photolysis is drug degradation due to light exposure.
What are zero-order kinetics?
The rate order is constant.
Drug degradation is constant, independent of the concentration.
What are the stability issues for biologics?
Biologics are more fragile than small molecules since they are larger and more bonds can break.
Biologics can lose activity if they unfold.
Biologics can aggregate resulting in increased/decreased potency and adversue immune responses.