Pharm Test 1 Lectue 4

Front 1

Draw Pen G or benyzl penicillin.

Back 1

Remember the beta lactam ring, the beta lactam bond, ad the thiazolidine ring.

Front 2

What is the advantage of Penicillin V over Penicillin G?

Back 2

Pen V is more acid stable and adsorbs less into food than Pen G

Front 3

When given as a drug, Pen G can be given as 2 couterions. What are the two possibilities?

Back 3

(1) Sodium
(2) Potassium

Front 4

What is a contraindication for giving Pen G as a sodium salt?

Back 4

If you have to give high concentrations of Pen G, then you wouldn't want to give the sodium salt to someone with hypertension.

Front 5

What is a contraindication for giving Pen G as a potassium salt?

Back 5

you wouldn't want to give the potassium salt to someone on cardiac glycosides

Front 6

When administering pen G intramuscurarly what are two possible salts it is administered as?

Back 6

(1) Procaine
(2) Benzathine

Front 7

What charge does procaine and benzathine have?

Back 7

Positive.

Front 8

How is procaine's and benzathine's solubility?

Back 8

® these have low solubilities, so they are injected intramuscularly and form a depot

Front 9

How often must you inject procaine and benzathine to sustaine a low blood concentration?

Back 9

you can get a sustained blood level with daily injections of procaine or weekly injections of benzathine; these salts only give a low blood concentration, so the infection being treated must be fairly susceptible to Pen G; unfortunately, if you encounter a Pen G toxicity, then there is no way to stop administration of the drug b/c the depot is already in you

Front 10

With oral administration of pen G what is the peak level? what about intramuscular administration?

Back 10

-oral administration of Pen G: peak blood level at 1 hr
-intramuscular injection: peaks in 30 mins

Front 11

What is the half life of penicillin G?

Back 11

30 minutes. after an hour, you will have eliminated the majority of the dose and after 3 hrs, there is essentially none left; this does not allow for plateau to be achieved very easily; in a serious infection, Pen G would need to be given intravenousloyto be absorbed,

Front 12

What does pen G bind to and does metabolism occur?

Back 12

Pen binds to albumin; very little metabolism occurs;

Front 13

How is Pen G eliminated?

Back 13

§ It is eliminated via the kidney, but only 10% is eliminated by glomerular filtration; the other 90% is eliminated via tubular secretion

Front 14

What drug is given to maintain pen G's blood concentration and how does it work?

Back 14

Probenecide is used to inhibit tubular secretion and maintain the blood levels of Pen over a longer period of time.

Front 15

What is probenecide also used to treat?

Back 15

probenecide is also used to tx gout by inhibiting uric acid uptake (increases the amount that is eliminated via urine)

Front 16

What is the distribution of pen G? BBB? Placenta?

Back 16

fairly good;
Pen does cross placenta, but it usually does not cross the BBB very well;
when meninges are inflamed, then the Pen crosses the BBB better

Front 17

During a hypersensitivity reaction, what do the major determinants react with? minor determinants?

Back 17

- major determinants react at the beta-Lactam bond (in orange)
- minor determinants react elsewhere on the penicillin

Front 18

Describe immediate hypersensitivity.

Back 18

- rxns that occur immediately (20 mins - 1 hr) are the most serious;
- they are caused by minor determinants and the IgE antibodies;
- these reactions can cause anaphylaxis and is an EMERGENCY

Front 19

What drugs are used to treat hypersensitivity?

Back 19

- primary drug used to tx these rxns is repeated IM injections of epinephrine into thigh every 5-15 mins until situation is under control
secondarily, you can also give antihistamine and glucocorticoid

Front 20

Describe a non-immediate hypersensitivity.

Back 20

- 1 hr - weeks later)
- caused by major determinants
- mediated by IgG and IgM
- tx with antihistamine and glucocorticoid
- see rashes, hives, etc.

Front 21

Besides hypersensitivities, what other toxicities are possible from pen G?

Back 21

Neurotoxicities:
which only occurs in high doses (20-60 million units)
if Pen builds up in CSF, especially in newborns or in people with neurological problems, then convulsions can occur

Front 22

What are the uses of pen G?

Back 22

(1) Streptococcal infections: Groups A, B, C, and G
(2) Strep. pneumoniae (causes childhood middle ear infections, but resistance has begun to develop)
(3) Neisseria: gonorrhea and meningitis (but resistance has begun to develop)
(4) Treponema pallidum (causes syphilis); no resistance
(5) Borellia burgodorfiri (Lyme disease)
(6) Bacillus anthracus (anthrax)
(7) Anaerobes: clostridium perfringens, Clostridium tetanii
(8) it is not good for treatment of (9) Bacteroides: Oropharyngeal strains(is the most frequently encountered oral bacterial infection)
but not good for GI strains

Front 23

How are most strains of staph resistant to pen G?

Back 23

§ most staph infections are RESISTANT to Pen G b/c they make penicillinase, a type of beta-lactamase

Front 24

What penicillins are penicillinase-resistant?

Back 24

- methicillin and nafcillin which are both parenteral (nafcillin concentrates in bile)

- oral ones include oxacillin, cloxacillin, and dicloxacillin

Front 25

Are the penicillinase-resistant penicillinas used as a first line of defense?

Back 25

- these drugs are not used as a first-line because Pen G is 10x more potent when treating non-resistant strains of bacteria

Front 26

In a gram positive bacteria, how is resistance formed?

Back 26

n a Gram-positive bacterium, there is a cytoplasmic membrane and outside this is the cell wall; within the cell wall, you have penicillin binding proteins (PBPs) such as the transpeptidase; if the beta-lactamase is unsuccessful (as is the case with using methicillin), then the bacteria can mutate the shape of the PBP so that methicillin cannot bind (not something the bacteria actively does, just randomly happens)

Front 27

In a gram negative bacteria, how is resistance formed?

Back 27

§ in Gram-negative bacteria, there is an outer membrane outside the cell wall; the outer membrane has channels called porins; Pen derivatives that tx Gram-neg must enter through the porins; the bacteria can mutate the pore so that Pen cannot enter

Front 28

How does MRSA become resistant?

Back 28

by mutating transpeptidase.