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Medical Biochemistry > Post Midterm Drugs > Flashcards

Post Midterm Drugs Flashcards

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USMLE® Step 1 flashcards
1
Q

Methotrexate

A

Folic acid analogue and competitive inhibitor of Dihydrofolate reductase. Inhibits reduction of dihydrofolate to tetrahydrofolate. Used to treat psoriasis, rheumatoid arthritis and neoplastic diseases.

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2
Q

Sulfanomides

A

PABA (p-aminobenzoate) analogue. Competitively inhibit the synthesis of folic acid in MICROORGANISMS and, thereby, decrease the synthesis of nucleotides needed for the replication of DNA

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3
Q

Trimethoprim

A

Inhibit dihydrofolate reductase thus preventing purine and pyrimidine biosynthesis. SPECIFIC FOR PROKARYOTES.

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4
Q

Aminopterin

A

Folic acid analogue and competitive inhibitor of Dihydrofolate reductase. Same as Methotrexate, except used less frequently. Folic acid analogues (in general) limit the amount of tetrahydrofolate available for use in purine synthesis and, thus, slow down DNA replication in mammalian cells. Therefore, useful for treating rapidly growing cells. Patients often experience anemia, scaly skin, GI and respiratory tract disturbances, and baldness.

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5
Q

Mycophenolic acid

A

A reversible, uncompetitive inhibitor of inosine monophosphate dehydrogenase. Mechanism: Deprives rapidly proliferating T and B cells of key components of nucleic acids.
Use: prevent graft rejection

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6
Q

Colchicine

A

Microtubule inhibitor.
Used for treatment of Gout. Does produce improvement but does not decrease serum uric acid levels. Probably inhibits migration of white cells to joints where uric acid crystals are phagocytized.

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7
Q

Allopurinol

A

A non-competitive inhibitor of xanthine oxidase. Causes excretion of hypoxanthine and xanthine (compounds more soluble than uric acid) instead of urate.

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8
Q

5-Fluorouracil

A

Converted to 5 fluorodeoxyridylic acid (dFUMP). Inhibits thymidylate synthase, thus preventing synthesis of dThymidine MP (dTMP) from dUMP.
Fluorine group on 5-fluorouracil is about the same size as a hydrogen atom, which makes this drug a uracil analogue.
Anti-cancer drug. In cancer cells, 5-fluorouracil is incorporated into RNA, which causes the RNA to be more detrimental or cancer cells than to normal cells.

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9
Q

Bromodeoxyuridine

A

Thymidine analogue. Anti-cancer

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10
Q

Trifluorothymidine

A

Thymidine analogue. Anti-cancer.

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11
Q

Heparin

A

Activates antithrombin III and inactivates thrombin

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12
Q

Warfarin

A
  • oral anticoagulant
  • blocks epoxide reductase in liver and prevents the regeneration of the active form of Vitamin K.
  • Inhibits the synthesis of the mature Vitamin K dependent clotting factors.
  • Slower acting than heparin
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13
Q

Streptokinase

A
  • Thrombolytic agent
  • Plasminogen activator
  • Converts plasminogen to plasmin enabling the dissolution of clots
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14
Q

Tamoxifen

A
  • Breast cancer treatment

- Needs activation by cytochromes in liver

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15
Q

Disulfiram

A

aka: Antabuse
1) Inhibits acetaldehyde dehydrogenase (therefore prevents Acetaldehyde conversion into acetate)
2) used for treatment of alcoholism
- meant to prevent alcohol consumption
3) Side effects: flushing, nausea

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16
Q

Celecoxib

A

Selective COX-2 inhibitor

  • could possibly increase the risk for platelet aggregation b/c when COX2 is specifically inhibited, less prostacylcin is produced, however COX1 is not inhibited and therefore thromboxane production continues. -> platelet aggregation.
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17
Q

Benoxaprofen

A

Inhibits 5-lipoxygenase (LOX)

  • 5-lipoxygenase catalyzes the rxn from aracidonic acid to 5-hyroperoxyeicosatetaeinoic acid (5-HPETE) which leads to the production of LH4 (Leukotriene).
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18
Q

Isoniazid

A

Anti-TB drug

-inactivates pyridoxine (PLP) which is required by ALA synthase (regulated enzyme in Heme formation)

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19
Q

Zileuton

A

Inhibits LOX (5-lipoxygenase) which converts arachidonic acid to HPETE in the formation of leukotrienes

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20
Q

What are examples of NSAIDs?

A

Aspirin (irreversible), indometriacin, phenylbutazone.

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21
Q

NSAIDs (non-steroidal anti-inflammatory drugs)

A

Reduce inflammation by inhibiting both COX-1 and COX-2. This decreases prostaglandins and thromboxanes.

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22
Q

Aspirin

A

Irreversible inhibitor of COX by acetylating serine residues.

Favors Prostacyclin by inhibiting thromboxane in platelets.

81mg

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23
Q

Name the two drugs that inhibit thromboxane synthase.

A

Dazoxiben and Dipyridamole. Used to prevent the synthesis of thromboxanes.

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24
Q

What is benzoic acid used for?

A

To treat hyperammonia by combining w/ glycine to form hippuric acid (excreted in urine-remove 1 nitrogen / molecule of benzoic acid

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25
Q

Significance of Phenylbutyrate

A

Used to treat hyperammonemia by removing 2 N/molecule.

Forms phenylacetate via B-oxidation which combines w/ glutamine to form pheylacetylglutamine (excreted)

26
Q

How is Lactulose used to treat acquired hyperammonia?

A

Lactulose forms a disaccharide that can only be digested by bacteria in the colon, forming lactic acid.

Lactic acid will be neautralized by NH4 therefore more N is excreted.

27
Q

How is Neomycin used to treat acquired hyperammonia?

A

Antibiotic; Reduces bacterial urease in gut so that less ammonia is formed in colon.

28
Q

Why is Sapropterin used to treat mild/ moderate forms of phenylketonuria (PKU)?

A

Synthetic form of tetrahydrobiopterin (BH4); given in massive doses to maintain association w/ mutant forms of phenylalanine hydroxylase that have decreased affinity for the BH4 cofactor.

29
Q

How are plant stanols/ sterols used to treat hypercholesterolemia?

A

They interfere w/ micelle formation in intestinal mucosal cells by displacing cholesterol thereby decreasing cholesterol intake / absorption. (found in some margarine)

30
Q

How does Ezetimbe treat hypercholesterolemia?

A

It decreases cholesterol absorption by blocking transporter protein.

31
Q

How are bile acids squestrants (resin) like cholestyrame used to treat hypercholesterolemia?

A

It blocks the enerohepatic uptake of bile acids by binding to bile acids/ salts so that they are excreted. Liver compensates by making more bile acids/ salts using cholesterol; this decreases overall serum LDL.

32
Q

Why are statins used to treat hypercholesterolemia?

A

It decreases cholesterol synthesis.

(Statins also decrease isoprenylation of proteins and synthesis of dolichol and CoQ bc these are all products of FPP (intermediate of cholesterol synthesis)

33
Q

What is the effect of Lead on heme synthesis?

A

Inhibits ALA dehydratase (porphobilinogen synthase) inhibiting heme formation. Also inhibits ferrochelatase, the last step of the heme synthesis pathway where iron is incorporated.

34
Q

What are examples of Statin drugs that treat hypercholesterolemia?

A
  1. Compactin
  2. Simvastatin (Zocar)
  3. Pravastatin (Pravachol)
  4. Lovastatin (Mevacor)
35
Q

What is Chenodiol (Chenodeoxycholic acid) and what does it treat?

A

It is a bile acid used to treat cholelithiasis, preventing the precipitation of of cholesterol in the gall bladder.

36
Q

Why is asparaginase used in treatment of some leukemia?

A

The enzyme will decrease serum asparagine levels which will starve the tumor.

37
Q

Why is L-DOPA given to pts w/ Parkinson’s disease?

A

Disease is due to loss of dopamine producing cells in basal ganglia. L-DOPA will be converted to dopamine in brain.

38
Q

How do anti-histamine drugs prevent adverse effects of allergic rxns?

A

They reduce the ability of histamine to function as a signal to other pathways (ex. receptor antagonist)

39
Q

What is Benodryl?

A

Anti-histamine drug that is a type of H1 (specific receptor) blocker.

40
Q

What is Zantac?

A

Anti-histamine drug that is a type of H2 (another specific receptor) blocker, also decreases production of HCl in stomach.

41
Q

Why is nitroglycerin used to treat MI/ angina pain?

A

It gets converted to nitric oxide which causes local vasodilation.

(Note: NO will also activate guanylate cyclase which will form cGMP which relaxes Bl vessels and increase Bl flow)

42
Q

How does aspirin lead to kernicterus in infants?

A

Aspirin pushes bilirubin from its binding site in albumin. This increase of bilirubin can’t be conjugated bc can’t be transported by albumin, resulting in jaundice in adults. Results in kernicterus / death in kids bc bilirubin can push thru Bl-brain barrier.

43
Q

Lifelong injection of intramuscular cyanocobalamin is given to pts w/ what condition and why?

A

To pts with pernicious anemia who can’t absorb B12 due to autoimmune destruction of partietal cells (hence no intrisic factor to absorb B12)

44
Q

What is phenytoin used for?

A

Inhibits intestinal conjugase causing foliate deficiency. Used to treat epilepsy

45
Q

Example and effect of sulfa drugs?

A

Sulfanilamide; inhibits folic acid synthesis.

46
Q

Why is phenobarbital given to pts w/ Crigler -Najjar II (Arias syndrome)?

A

Will induce enzyme bilirubin glucorunyl transferase which conjugates bilirubin.

enzyme only has 10-20% normal activity in this syndrome

(Note: syndrome causes inherited hyperbilirubinemia)

47
Q

How does benzodiazepine ( ex. Valium) decrease anxiety?

A

Acts like GABA by binding to GABA receptor

48
Q

What is Phenylclidine (PCP)?

A

Hallucinogen in people/ tranquilizer in animals by acting as antagonist of NMDA (glutamate) receptor.

49
Q

What is the effect of phenobarbital on CYP (cytochrome P450)?

A

it induces synthesis of CYP by 3-4 folds in 4-5 days and also stimulates heme synthesis for CYP.

(Note: Cyt P450 aka CYP metabolizes drugs making them more polar to be excreted, absorbed or inactivated)

50
Q

Why wouldn’t we give phenobarbital to pts with AIP (Acute intermediate porphyria?

A

Drug will stimulate Cyt P450 synthesis therefore stimulating heme synthesis. AIP due to deficiency HMB synthase therefore will cause buildup of intermediates of heme synthesis. Worsen symptoms of AIP and lead to death.

51
Q

Acetadote (N-acetyl cysteine) is used to treat what type of poisoning and why?

A

Injection of acetadote treats acetaminophen poisoning bc drug binds directly to NAPQ1 (toxic intermediate) of tylenol due to alcohol consumption. Helps it to be excreted.

52
Q

Why is disulfiram (antabuse) used in treatment for alcoholism?

A

Inhibits ALDH preventing formation of acetate, resulting in high levels of acetaldehyde. Pt experiences flushing/ nausea-prevent pt from consuming alcohol.

53
Q

What is Fomepizole?

A

Competitive inhibitor of ADH. Used to treat methanol, ethylene glycol (anti-freeze) and alcohol poisoning.

54
Q

What is the role of avidin and where is it found?

A

Found in raw egg whites; can inhibit absorption of biotin.

55
Q

What does hypoglycin A and where is it found?

A

In unripe ackee fruit; inhibits MCAD which results in decrease in B-oxidation. Associated with Japanese vomiting sickness (hypoglycemia, vomiting, coma, death)

56
Q

Why do diabetic patients take metformin?

A

Decreases glucose output of liver and increases glucose utilization by muscle. Overall effect: improve insulin resistance.

57
Q

What is the effect of Sulfonylurea on insulin?

A

It increases insulin secretion from pancreas by stimulating B cells release insulin.

58
Q

What occurs when a pt without Diabetes consumes Sulfonylurea?

A

Results in high levels of insulin, C-peptide, and proinsulin; pts will have factitious hypoglycemia (produced artificially)

59
Q

What does Sibutramine do?

A

Used to manage obesity by suppressing appetite

60
Q

What is the role of Orlistat?

A

Inhibits gastric and pancreatic lipase therefore inhibiting digestion / absorption of TAGs; used to manage obesity

61
Q

What is the fxn of pilocarpine?

A

Stimulates sweat glands; used in sweat chloride test to measure Cl concentration; used to diagnose cystic fibrosis

Medical Biochemistry (35 decks)

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