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Pharmacology -- Test #2 > Clindamycin and Tetracycline Antibiotics > Flashcards

Clindamycin and Tetracycline Antibiotics Flashcards

1
Q

Clindamycin is synthesized from…

A

naturally occuring Lincomycin by treatment with Chlorine and Triphenylphosphine

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2
Q

Why isn’t Lincomycin used anymore?

A

Toxicity

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3
Q

Clindamycin mechanism of action

A

Inhibition of protein synthesis by binding the 23S RNA part of the 50S ribosomal subunit.

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4
Q

Reason to expect antagonism/cross-resistance between clindamycin and erythromycin?

A

It has the same binding site on the ribosome

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5
Q

Clindamycin is most effective against

A

Aerobic G+ Cocci

Anerobic G- bacilli

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6
Q

Most common uses for Clindamycin

A 
S. aureus bone infection
Topically for severe acne
Cream for bacterial vaginosis. 
Lung abscess
MRSA
Toxoplasma gondii in AIDS patients
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7
Q

When Clindamycin is used to treat AIDS patients, what other drugs are added

A

Pyrimethamine and Leucovorin

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8
Q

What is an important limiter of Clindamycin use?

A

It increases the incidence of C Diff pseudomembranous colitis

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9
Q

Dosage form of Clindamycin

A

Oral administration
IV (Clindamycin phosphate)
Topical foams/solutions)

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10
Q

Clindamycin is metabolized extensively by…

A

Cytochrome P450 enzymes in liver

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11
Q

Breakdown products of Clindamycin?

A

Sulfoxide

N-Demethylated Derivative

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12
Q

Approx __% of Clindamycin is absorbed in the GI

What about Clindamycin’s PK makes it especially useful

A

90

Can get through the BBB

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13
Q

Adverse effects of Clindamycin

A

Diarrhea, pseudomembranous colitis, nausea, vomiting, cramps, rash
Possibly contact dermatitis

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14
Q

Effects of pseudomembranous Colitis?

Treatment?

A

Diarrhea, Colitis, Toxic Megacolon

Metronidazole or Vancomycin

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15
Q

Tetracycline is produced by

A

Streptomyces

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16
Q

What happens when tetracyclines are exposed to polyvalent ions? Examples of polyvalent ions?

A

Tetracyclines for stable chelates

Ca++, Al+++, Cu++, Mg++

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17
Q

Consequences of Tetracycline forming insoluble chelates?

A

Can’t be administered with high calcium foods, antacids with multivalent metals, hemainics containing irons.

Can’t give to kids or it will mess up their teeth

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18
Q

Preferred route of administration for Tetracycline

A

Oral

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19
Q

Why can’t little kids use Tetracycline?

A

Tetracyclines chelate Ca during formation of teeth, causing them to be permanently brown or gray.
Discoloration gets worse over time from photooxidation

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20
Q

Why does it hurt to inject Tetracyclines?

A

Formation of insoluble Calcium complexes

Minimize with EDTA to chelatate Ca and buffered to acidic pH

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21
Q

What happens as a result of the hydrogen on the amine-bearing Carbon of Tetracycline?

A

Enolization

Epimerization

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22
Q

In the epimerization reaction, Hydrogen coming in from above will generate _____ and below will generate ______

A

Tetracycline

Epitetracycline (Inactive)

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23
Q

Why should we care about the Tetracycline epimerization reaction?

A

This is how old Tetracycline products can lose approximately half of their potency.

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24
Q

When is epimerization of Tetracycline slow? fast?

A

Slow – Solid State

Fast – pH 4.0

25
Q

What side group is especially set up to cause the dehydration reaction to occur?

A

The tertiary benzylic hydroxyl group at C6

26
Q

End result of Tetracycline dehydration reactions

A

Anhydrotetracycline – Inactive
or
4-Epianhydrotetracycline – Inactive and Toxic

27
Q

Whats so bad about 4-Epianhydrotetracycline?

A

Toxic to Kidneys

Produces Fanconi-like syndrome (Failure of reabsorption in PCT)

28
Q

Perk of Tetracycline derivatives without a C6 group?

A

No risk of dehydration toxicity

29
Q

What happens to Tetracycline in pH 8.5 or above?

A

Generates a lactone product that is inactive.

30
Q

Tetracycline mechanism of action

A

Bind the 30S ribosomal subunit and inhibit bacterial protein synthesis. Block attachment to the A site.

31
Q

Do Tetracycline and Erythromycin interact competitively?

A

No, their binding sites do not overlap with eachother

32
Q

Why doesn’t Tetracycline trash the ribosomes of the host?

A

It can in super high doses, but usually won’t be dosed high enough to. Bacteris have an uptake mechanism that makes Tetracycline especially effective against them.

33
Q

Name the ribosomal site Tetracycline primarily binds to

A

Tet1

34
Q

Therapeutic use of Tetracyclines?

A

Broad Spectrum Antibiotics
Acne
Chlamydia, Rickettsia, Brucellosis, Spirochetal
Anthrax, Plague, Tularemia, Legionaire’s

35
Q

Tetracycline is made by _______
Perks?
Cons?

A

Streptomyces aureofaciens
Generic, inexpensive
Food and Milk drop absorption by 50%

36
Q

What is Dimeclocycline?

A

Tetracycline, but with a secondary hydroxyl at C6 instead of a tertiary hydroxyl.

37
Q

Benefit of Dimeclocycline’s change to a secondary hydroxyl?

A

It dehydrates more slowly because the secondary cation intermediate formed is less stable than the tertiary cation intermediate

38
Q

Con of Dimeclocycline?

A

Food and Milk lower absorption by about 50%

39
Q

What is Minocycline?

A

Dimeclocycline modified to lost the c6 hydroxyl group

40
Q

perks of Minocycline?

A

No C6-hydroxyl means no acid-catalyzed dehydration
No potential for 4epi…. toxicity
90-100% bioavailability

41
Q

Cons of Minocycline?

A 
Absorption down 20% when taken with food or milk
Vestibular toxicities (vertigo, ataxia, nausea)
42
Q

Oxytetracycline is made by

A

fermentation of Strep. rimosis

43
Q

Important details for Oxytetracycline?

A

It fuckin sucks.

pretty much replaced now.
Most hydrophillic tetracycline.

44
Q

Important structural details of Doxycycline?

A

It lacks a C-6 hydroxyl – no dehydration = no toxicity

45
Q

Bioavailability of Doxycycline?

With food/milk?

A

90-100%

Absorption lowered by approx. 20% when taken with food/milk

46
Q

Half life of Doxycycline?

A

18-22 hours

47
Q

First antibiotic to be manufactured synthetically on a large scale?

A

Chloramphenicol

48
Q

Why don’t people use Chloramphenicol so much anymore?

A

Toxicities

Still prevalent in the 3rd world because cheap

49
Q

How does Chloramphenicol work?

A

It binds reversibly to the 50S ribosomal subunit near the erythromycin and clindamycin spot (competitive interactions occur). Specifically, it blocks peptide bond formation btw the P and A sites

50
Q

Therapeutic use of Chloramphenicol?

A

Ointment/Eye drops

IV in severe disease states

51
Q

Indications for IV Chloramphenicol

A

Bacterial Meningitis
Typhoid Fever
Rickettsial infections
Intraoccular infections

52
Q

How does resistance to Chloramphenicol happen?

A

Reduced membrane permeability
50S Ribosome Mutation
Elaboration of Chloramphenicol acetyltransferase

53
Q

What does Chloramphenicol acetyltransferase do?

A

Acetylates one/both ydroxyl groups to form metabolites that can’t bind 50S

54
Q

Toxicity risks for Chloramphenicol?

A

Aplastic Anemia
Bone Marrow Suppression
Childhood Leukemia
Nausea, Vomiting, Diarrhea

55
Q

Why does it take months after Chloramphenicol treatment to see Aplastic Anemia symptoms?

A

RBC life is 3-4 months

Takes time for the loss of new blood cells to be apparent

56
Q

Highest risk way to use Chloramphenicol? Lowest?

A

Highest – Oral

Lowest – eye drops

57
Q

How is Chloramphenicol metabolized?

A

Metabolized to glucuronide in the liver

Pharmacologically inactive and readily excreted

58
Q

Mechanism for Chloramphenicol metabolism?

A

Nucleophilic attack of the less hindered primary alcohol of UDPGA, performed by glucuronyl transferase.

59
Q

Can babies have Chloramphenicol?

A

No. Neonates can’t metabolize it.

Pharmacology -- Test #2 (13 decks)

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