Walters - Penicillins Flashcards
what is a beta lactam
4 membered cyclic amide; essential for activity of Penicillins
what makes up Penicillin? is it static or cidal?
Thiazaolidine + beta lactam rings. It is cidal bc it disrupts cell wall synthesis causing lysis
what does the side chain determine
the properties and spectrums of activity
what is the mechanism of action of penicillin
inhibit transpeptidase (Pcn binding protein) which would normally help make cell wall of bacteria by removing D alanine
What is peptidoglycan composed of?
- N acetylglucosamine
- N acetylmuramic acid
* NAG and NAM
penicillins are only effective against organisms that synthesize peptidoglycan. They are ineffective against ____ and protozoa
fungi
what is the main mechanism of resistance
beta lactamase enzymes (Pcnases); break open the beta lactam ring which makes antibiotic ineffective
What is penicillin G aka Benzyl Penicillin and how is it given?
Given parenterally, (IV or IM) not orally. Will enter CNS if meninges inflamed.
What are the 3 forms of penicillin G?
- Aqueous: solution; given via IV
- Procaine: suspension; given via IM
- benzathine: suspension; given via IM
What is procaine
An ESTER that is a local anesthetic that combines with Penicillin and slows its absorption and helps numb the pain of injection. It is also available with benzathine as Bicillin C-R
This form of Penicillin G is the longest acting
Benzathine
How is pencillin eliminated
by tubular secretion.
Penicillin is the only antibiotic that is not given in mg but in _____. 1 unit = 0.6 micro grams. 1 million units = _____mg. If given 2.4 million units of benzathine penicillin, how many mg is this?
units; 600;
1440 mg. (2.4 x 600)
what organism causes syphillis?
Treponema pallidum
What are characteristics of Penicillin V aka Phenoxymethyl PCN
- given orally!
- less active
- acid stable
- dosed in mgs!
- Food will decrease absorption. need to give 1 hour before/1 hour after meal
What penicillins would you prescribe for microbes that don’t respond to penicillin G or V?
-Beta lactamase Resistance PCNs (DON)
- Dicloxacillin: given orally
- Oxacillin: given parenterally
- Nafcillin: given parenterally
How are beta lactamsae resistant pcn’s excreted
biliary and renal excretion
Staph. areus that resist “DON” are called:
methicillin resistant (MRSA); although the drug methicillin was discontinued years ago due to nephrotoxicity
What are aminopenicillins
extended spectrum PCN’s but with gram negative coverage. They are still susceptible to penicillinases. Strains that resist penicillin resist amino penicillins
what are the type of aminopenicillins
- Ampicillin
2. amoxicillin
Ampicillin is available with _____ as Unasyn for IM/IV use which is a preferable form for peritonitis due to ____ fragilis; a gram negative rod that is part of the normal flora and is a big producer of beta lactamases
sulbactam; bacteroides
what is a mechanism for sulbactam
inhibit beta lactamase and protects the drug from metabolism thus enhancing its activity.
What are characteristics of amoxicillin
only available orally; better oral absorption and longer half life. Not used for initial treatment of peritonitis bc it can undergo absorption unike ampicillin which is given via IV
what is amoxicillin available with
clavulanate; as augmentin
