Penicillin I Flashcards
What was the first penicillin with anti-pseudomonal properties?
carbenicillin
What is a popular penicillin combination drug in use in hospitals today (trade name Zosyn)?
piperacillin and tazobactam
Augmentin contains a combination of…
amoxicillin and clavulanic acid
What are six characteristics of the ideal penicillin?
stability at low pH (ie in the stomach), slower renal elimination, stability against beta lactamases, broader antimicrobial coverage, better penetration into CSF, no hypersensitivity reactions
What is the half-life of most penicillins?
2 hours
Which renal filtration method contributes more to the elimination of beta lactams, glomerular filtration or tubular secretion?
glomerular filtration
Penicillin G is mostly active against gram ______ organisms
positive
Penicillin G is also known as….
benzylpenicillin
What organisms does Penicillin G have good activity against?
group A streptococcus, group B streptococcus (ex.: S. agalactiae), S. viridans, S. pneumoniae (although resistance increasing)
What organisms does Penicillin G have moderate activity against?
enterococci gram negative aerobes
Penicillin G is a drug given _______
intravenously
Which aqueous salt form of Penicillin G is most commonly dispensed?
potassium (Penicillin GK)
How many milliequivalents of potassium are present per million units of Penicillin GK given?
1.7 mEq
Too much potassium can cause what major health problem?
cardiac arrest
How often must Penicillin GK be given for serious infections and why?
every 4 hours, because it is quickly eliminated
How many million units per day of Penicillin GK is considered a high dose?
24 MU
Which two formulations of Penicillin G are suspensions and only suitable for intramuscular injection?
Procaine Penicillin G, Benzathine Penicillin G
Which Penicillin G suspension is not used much anymore because of hypersensitivity issues?
Procaine Penicillin G
Which Penicillin G suspension is very long-acting?
Benzathine Penicillin G
Why is Benzathine Penicillin G so long acting?
it deposites a reservoir of drug in the muscle that must slowly diffuse into the blood, so only a little penicillin leaks into the blood at a time
What is Benzathine Penicillin G effective in treating?
all stages of syphillis, prophylaxis for rheumatic fever, sometimes Strep pharyngitis
What is the formulation of Penicillin G meant to be used as an oral dose?
Penicillin V
What makes Penicillin V effective as an oral dose?
it is designed to resist acid hydrolysis (like in the stomach), so oral bioavailability much higher
Is it better to take Pencillin V on an empty stomach (1 hour before or 2 hours after meals) or with food?
on an empty stomach
Which compound, although not a penicillin, is usually taken with penicillin V because it increases the bioavailability?
probenecid (benemid)
How does probenecid increase the bioavailability of Penicillin V?
it blocks selective tubular secretion of pencillins, increasing their half-lives
When should you take probenecid?
30 minutes before antibiotic
Where does selective tubular secretion take place in the kidneys?
peritubular capillaries
What percentage of people who take penicillins exhibit hypersensitivity reactions?
10%
What percentage of people “outgrow” their penicillin allergy (do not have a reaction after taking penicillin at least 10 years after their initial reaction)?
80%
What is the difference between hives and flat, blotchy rashes?
hives are raised bumps, happen almost immediately and progressively get worse; flat, blotchy rashes not raised, may not occur until several days after starting therapy (of less concern)
What Pregnancy Risk Factor are penicillins placed in and how does it affect therapy in pregnant patients?
Pregnancy category B, probably safe to use in pregancy (low risk)
What three pregnancy categories indicate drugs that should NOT be used in pregnant patients without very good reason?
pregnancy category C, D, X
Anti-staphylococcal penicillins are also called __________
penicillinase-resistant penicillins
What is the preferred anti-staphylococcal penicillin in use today (not active against MRSA)?
nafcillin
Why is methicillin no longer used in treatment?
issues with interstitial nephritis
Methicillin and Nafcillin are only useful as ________ agents because of their poor absorption from the GI tract.
parenteral
What is unique about the elimination of anti-staphylococcal penicillins?
they are eliminated primarily through the renal pathways but also through the biliary pathway, therefore the dose doesn’t need to be adjusted in patients with renal failure; the liver sends the drug into the biliary duct which drains into the intestine
What is the class of anti-staphylococcal penicillins designed for oral dosing?
isoxazolyl penicillins
Which anti-staphylococcal penicillin is available as an IV, IM, and oral dose?
oxacillin
Why can isoxazolyl penicillins be dosed orally?
they are specifically designed to resist acid hydrolysis
What differentiates cloxacillin and dicloxacillin from oxacillin?
cloxacillin/dicloxacillin only available as oral doses, have chlorine groups (1 in cloxacillin, 2 in dicloxacillin) added to them which dramatically increases bioavailability
What three additional organisms (besides those already covered by Penicillin G) does ampicillin cover?
escherichia coli, haemophilus influenzae, proteus mirabilis
What are two aminopenicillins?
ampicillin, amoxicillin
Of the aminopenicillins, _______ is available in IV, IM, and oral doses, while _________ is only available as an oral dose.
ampicillin, amoxicillin
