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Pharm Exam 4 > Anti-Metabolites > Flashcards

Anti-Metabolites Flashcards

1
Q

What are the anti-metabolites ?

A

Folate Antagonists

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2
Q

What is Tetrahydrofolic acid?

A

Acid required for DNA/RNA synthesis (purine and pyrimidine synthesis)

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3
Q

What happens to the folic acid that humans receive from their diet?

A

It get converted to DHF

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4
Q

How do bacteria synthesize Folic acid?

A

They use paraminobenzoic acid (PABA) to synthesize DHF then DHF converts it to THF

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5
Q

Name the 6 PABA analogs inhibitors.

A
  1. Sulfamethazole–newer
  2. Sulfasalazine–GI
  3. Silver Sulfadiazine-topical
  4. Sulfisoxazole-ophthalmic
  5. Dapsone-leprosy
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6
Q

Name the 3 DHF reductase inhibitors.

A
  1. Trimethoprim
  2. Pyrimethamine
  3. Proguanil (Also Methotrexate)
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7
Q

Name the 2 combinations.

A
  1. Cotrimoxazole

2. Fansidar

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8
Q

What is Cotrimoxazole (Bactrim/Septra) a combination of?

A

Trimethoprim + Sulfamethoxazole

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9
Q

What is Fansidar a combination of?

A

Sulfadoxine + Pyrimethamine

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10
Q

Are the Sulfa PABA Analogs STATIC or CIDAL?

A

STATIC

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11
Q

What are the Sulfa PABA Analogs active against?

A

Gram (+) and gram (-)

  1. Selected enterobacteria (UTI)
  2. Chlamydia
  3. Pneumocystis
  4. Nocardia
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12
Q

If given topically, what are the Sulfa PABA drugs are used for?

A

prevent infections of burns

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13
Q

What can you treat newborns with prophylactically if there is a Trachoma (Chlamydial) inf?

A

Erythromycin ointment or silver nitrate solution

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14
Q

What is the most common cause of preventable blindness?

A

Chlamydia

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15
Q

How are Sulfa-PABA drugs absorbed?

A 
very well orally 
EXCEPT: 
Sulfasalazine (chronic bowel disease) 
and 
Succinylsulfathiazole (salmonella and shigella carriers)
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16
Q

Which Sulfa-PABA drug is given topically to decrease burn sepsis but has a superinfection risk with fungi?

A
  1. Silver sulfadiazine

2. Mafenide (sulfamylon) but this is painful

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17
Q

Do the Sulfa-PABA analog drugs penetrate the CSF?

A

yes; even without inflammation

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18
Q

Do the Sulfa-PABA analog drugs penetrate the placental barrier?

A

Yes

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19
Q

There are 2 other important places the Sulfa PABA analog drugs go into besides the CSF and placenta–what are they?

A
  1. Breast milk

2. Bound to serum albumin

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20
Q

Why should we be worried that the Sulfa-PABA analog drugs get bound to the serum albumin?

A

In a newborn, it can cause kernicterus by displacing the bilirubin

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21
Q

What 2 drugs do the Sulfa-PABA drugs interact with?

A
  1. Increase Warfarin

2. Methotrexate

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22
Q

Which drug can cause crystalluria? And how does this happen?

A

Sulfa PABA analog drugs

they can precipitate at neutral or acidic pH then that causes the cystalluria

23
Q

Since crystalluria is nephrotoxicity, what can you instruct the patient to do to prevent this?

A
  1. Adequate hydration

2. Alkalization of urine –> drug ionization

24
Q

Which Sulfa PABA analog drugs are more soluble at urinary pH and thus, have less chance of crystalluria?

A
  1. Sulfisoxazole

2. Sulfamethoxazole

25
What are some hypersensitivity reactions of the Sulfa PABA analog drugs?
1. Rashes 2. Photosensitivity 3. Angioedema (Urticaria and edematous areas)
26
What adverse effect will you expect from a longer acting Sulfa PABA drug?
Stevens-Johnson Syndrome
27
Which diuretics do the Sulfa PABA drugs have cross reactivity?
1. Acetazolamide 2. Thiazides 3. Furosemide Bumetanide
28
Which antihypertensive drugs have cross reactivity with the Sulfa PABA drugs?
Diazoxide
29
Which hypoglycemic agents have cross reactivity with Sulfa PABA drugs?
The Sulfonylureas: 1. Tolbutamide 2. Glyburide 3. Glipizide
30
Which classes of drugs have cross reactivity with the Sulfa PABA drugs?
1. Diuretics 2. Antihypertensive drugs 3. Sulfonylurea hypoglycemic drugs
31
What hemopoietic disturbances do the Sulfa PABA analog drugs have?
1. Hemolytic anemia G 6 PD deficiency 2. Granulocytopenia 3. Thrombocytopenia
32
What kind of drug potentiation do the Sulfa PABA analog drugs have on: 1. Tolbutamide: ? 2. ?: increases anticoagulation 3. ?: increases toxicity 4. Increased free bilirubin
1. increases hypoglycemic effect 2. Warfarin 3. Methotrexate 4. Kernicterus
33
What contraindications do the Sulfa PABA analog drugs have?
1. Pregnant and lactating women 2. Avoid Sulfa-PABA drugs in newborns 3. Pts taking Methamine
34
Why should Sulfa PABA analogs be avoided in newborns?
Because the bilirubin will get displaced by the drug, causing the bilirubin to enter the CNS causing mental dysfunction
35
Why would you not give a patient taking methamine a Sulfa PABA drug?
Because the Sulfonamides condense with formaldehyde
36
A mutated bacterial dihydropteroate synthetase is a resistance mechanism to which drug?
Sulfa PABA drugs
37
What is Trimethoprim?
Potent inhibitor of bacterial dihydrofolate reductase (DHFR) decreases folate coenzymes for dna/rna synthesis
38
T or F: Trimethoprim has an antibacterial spectrum similar to the sulfonamides but 2x as stronger
False: they are 20-50x stronger
39
What is the MOA of Trimethoprim?
Bacterial reductase
40
What is nice about Trimethoprim?
It has good selective toxicity
41
Which drug is Trimethoprim most often compounded with?
Sulfamethoxazole
42
An altered dihydrofolate reductase with decreased affinity for the drug is a resistance mechanism for which drug?
Trimethoprim
43
Which drug has increased concentrations in prostatic and vaginal fluid along with a folate deficiency?
Trimethoprim
44
What is an effect of the folate deficiency using the treatment of Trimethoprim?
Megaloblastic anemia
45
How do you treat the megaloblastic anemia caused by Trimethoprim?
reverse with concurrent folinic acid (leucovorin)
46
What is the benefit of treating a pt with Co-trimoxazole?
Synergism: inhibition of 2 sequential steps-- 1. competitive inhibition of folic acid synthesis (PABA analog) 2. Selective inhibition of bacterial dihydrofolic acid reductase
47
What combination is Fansidar?
Pyrimethamine + Sulfaxodine
48
Why would you need to use Fansidar?
Chloroquinine-resistant malaria
49
What is the benefit of Fansidar?
Synergism: inhibition of 2 sequential steps-- 1. competitive inhibition of folic acid synthesis (PABA analog) 2. Selective inhibition of bacterial dihydrofolic acid reductase
50
What are some adverse reactions to Fansidar?
1. Rash 2. N/V; glossitis, stomatitis 3. Megaloblastic anemia 4. G6PD-deficiency = hemolytic anemia 5. HIV + pneumocystitis + Bactrim = drug fever, rashes, diarrhea, maybe pancytopenia
51
What 3 drugs should you have caution with when prescribing Fansidar?
1. Warfarin 2. Phenytoin 3. Methotrexate ALL increase
52
What are some common therapeutic uses for Fansidar?
1. UTI 2. Bacterial Respiratory Tract inf 3. Pneumocystis carinii pneumonia (PCP) 4. GI inf 5. Mild burns, topically
53
If you are treating mild burns with Fansidar, HOW should it be administered?
Topically

Pharm Exam 4 (10 decks)

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