Pharm Topic 15: Sulfonamides, Trimethoprim, And Quinolones

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Sulfonimides pharmacokinetics (admin, distrib, elim, protein)

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Admin: Can be given orally. Can be given ophthomolically
Distrib: Can get to CNS and Cx placenta
Elim: Metabolized by liver via acetylation, excreted in urine.
Protein: Yes is bound.

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Sulfonamides Mech

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Static. Act as competitive inhibitors of PABA which is a substrate for dihydropterotate synthetase. This is an enzyme Folic Acid pathway, therefore inhibits folic acid synth which is necessary for DNA replication. (humans dont have enzyme, get folic acid from diet).

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Sulfonamides Side effects

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1) Allergic Rx - Can occur at all organ sites and lead to steven-johnson syndrome.
2) UT disorders - via crystalluria and possible occlusion by the granules
3) Hematopoetic disorders - Can get aplastic anemia, thombocytipenia, eosinophilia, and hemolytic anemia in g6pd deficient peeps)
4) Kernicterus - Brain damage in g6pd deficient fetuses.

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Sulfonimide Drug interactions

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Rxs with anti coags, anti convulsants, and hypoglycemic agents increase sulfonimides availability. Can be displaced from albumin. Coumadin is common interaction. Antacids can reduce absorbtion.

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Sulfonimide Resistance

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1) Altered enzyme with lower drug affinity
2) Overproduction of PABA
There is Cx resistance among sulfonimides.

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Sulfonimides Spectrum

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Broad spectrum, G+ and -. Only used when effectiveness is superior to other drugs. Used to treat:
UTIs
Burn victims
Used with Trimethoprim for lots of things

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Sulfadiazine

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Used to treat UTIs and Toxoplasma in immunocomprimised. Silver sulfadiazine is used as an ointment for burn patients.

Front 8

Sulfisoxazole

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Used for UTIs, otitis media, and as an amoxicillin alternative in kids.

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Sulfamethoxazole

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Used with trimethoprim, for UTIs, otis media, and bronchitis.

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Sulfacetamide

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Administered as eye drops for eye infections

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Sulfasalazine

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Used in treatment of ulcerative collitis and chrons disease. Absorbed poorly so active in lower bowel, while metabolite becomes an Ab, is not used as one.

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Trimethoprim-Sulfamethoxazole Mech

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Trimethoprim inhibits dihydrofolate reductase, inhibiting dihydrofolate synth. Along with Sulfamethoxazole, both block different steps in the folic acid pathway. Have a 4 fold synergism effect.

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Trimethoprim-Sulfamethoxazole Spectrum

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Works against G+/-, inactive against anaerobes.
-Combo used for:
MRSA (neither effective alone)
e.coli (obtains resistance much slower to combo)
Respiratory tract infections (influenza, pneumocystis)
Listeria

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Contrimoxazole

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Name for Trimethoprim-Sulfamethoxazole

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Prymethamine

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Dihydrofolate Inhibitor. An antimalarial

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Methotrextate

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Dihydrofolate Inhibitor. potent antimetabolite used to induce immunosuppression or treat cancer.

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Quinolones Pharmacokinetics (admin, distrib, elim, protein)

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Admin: Can be taken orally, antacids, metals, and divalent cations decrease absorbtion.
Distrib: Most Cx placental barrier and enter CNS
Elim: Levo, gati, and ofloxin are all excreted in urine unchancged. Nalidixic acid and cipro undergo metabolism and are urine excretion. Moxifloxin is all liver excretion.
Protein: Variable from 20-90%

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Quinolones Mech

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Cidal. Inhibit bacterial DNA gyrase. Flouroquinolones act by inhibiting DNA gyrase and Topoisomerase 4.

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Quinolone side effects

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Generally well tolerated.
CNS - headache, mood change, delirium, seizures.
Can cause tendonitis/tendon rupture.
Floroquinones can cause phototoxicity via UVA light.
Not for children <18 or pregnant women b/c can cause cartilage damage.
Prolongs QT, therefore contraindicated for peeps at risk for QT prolongation.

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Quinolone spectrum

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1st gen (nalidixic acid) is only useful for enterobacteria. Flouroquinolones have broad +/- spectrum. Used for UTIs, prostatis, GI infection, Staph infection, and respiratory infections.

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Quinolone Resistance

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Resistance to one usually means resistance to all:
1) Mutations to Gyrase or topoisomerase 4
2) Pump drug out of bacteria
3) Decrease outer membrane permeability preventing drug entrance.

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1st gen quinolones (ex and uses)

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Nalidixic acid. Only used for UITs, only effective against enterobacterea

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2nd gen flouroquinolones (ex and uses)

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Ciproflaxin and ofloxacin. Have increased G- and + activity. Can penetrate bone and treat pseudomonas. Used for GI, UTI, STD, and skin infections.
Not used for Streptococci or pneumonia

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3rd/4th gen flouroquinolones (ex and uses)

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Levofloxacin, gatifloxacin. More G+ coverage, work against strep, pneuomia, and bronchitis.
Moxifloxacin has added anaerobic coverage but poor pseudomonas coverage and no urine excretion therefore not for UTIs.