Intro & Sulfonamides - Walters Flashcards
What should you consider when choosing an antibiotic?
- Resistance
- Age
- Hepatic function
- Genetics
- Disease state
- Pregnancy
- Site of infection
- Route of administration
Sulfonamides
Broad spectrum STATIC antibiotics vs G+ and G- organisms
What is the rationale behind multiple Rx therapy?
- Decreased risk of selecting for resistant organisms
- Multiple organism infections not covered by a single Rx
- Synergism - when two drugs produce an effect greater than the sums of either drug alone
What is the mechanism of sulfonamides?
Structural analogs of PABA and as such, inhibit dihydroteropate synthase (the first step in synthesis of folic acid)
What is commonly used with sulfas for a synergistic effect?
DHFR inhibitor (this reduces FH2 back to FH4; inhibits thymidine synthesis; inhibits organismal DNA synthesis)
Trimethoprim
- Bacterial DHFRI
* Side effects: blood dyscrasias
Primethamine
- Protozoal DHFRI
* Antimalarial
Methrotrexate
- Mammalian, bacterial and protozoal DHFRI
* Used to treat psoriasis and various cancers
Pralatrexate
DHFRI used to treat T cell lymphomas
Sulfosoxazole
- Oral sulfonamide
* Used w/erythromycin for otitis media
Sulfamethoxazole
- Oral sulfonamide
- Used only w/trimethoprim for various urinary, respiratory and GI infections
- Aka Co-trimoxazole; TMP-SMZ
Sulfacetamide
- Topical sulfonamide
* Used for ulcerative blepharitis and bacterial conjunctivitis (eye stuff)
Silver sulfadiazine
- Topical sulfonamide
- Used for burns and to prevent sepsis
- Silver released is toxic to microorganisms
- CAUTION: potential for extensive systemic absorption
Mafenide
- Topical sulfonamide
- Used for burns
- Limited use because can cause metabolic acidosis by inhibiting carbonic anhydrase (leads to loss of HCO3 → loss of buffering capacity)
What are some general side effects of all sulfonamides?
- Crystalluria
- Kernicterus
- Blood dyscrasias
- Hypersensitivity
- Hyperkalemia
Crystalluria
- Crystal formation in nephrons of kidneys
* Incidence low but still recommend drinking lots of water with oral dosage forms to minimize risk of nephrotoxicity
Kernicterus
- Bilirubin encephalopathy
- A form of jaundice from displacement of bilirubin from plasma proteins
- Free bilirubin enters CNS & deposits in basal ganglia & other areas → generalized CNS depression
Blood dyscrasias
- Acute hemolytic anemia (most serious), agranulocytosis, aplastic anemia
- Rare but can be fatal
- Do not use topicals if there is a known Hx of blood dyscrasias
Hyperkalemia
- Too much potassium in blood
* Mainly if there is a co-morbidity
Who should NEVER take sulfonamides?
Pregnant ladies during the last months of pregnancy, newborns and infants < 2 years old
Erythema multiforme
- Hypersensitivity disorder
* Sudden onset of asymptomatic macules, papules & vesicles on extremities and face
Stevens-Johnson syndrome
- Hypersensitivity disorder
- Fever, headache, cough & conjunctivitis followed by macules on face, neck & other areas eventually forming bullous eruptions on skin & mucous membranes
Rx fever
- Hypersensitivity disorder
* Immune-mediated hypersensitivity phenomenon
Why should kids not be given tetracyclines?
Because it can permanently discolor teeth
Which drug is nephrotoxic and ototoxic?
Aminoglycosides
Which drugs have a higher risk of causing hemolysis if low levels of G6PD?
- Sulfonamides
- Nitrofurantoin
- Chloramphenicol
Which drugs can give you a false + for urine sugar?
- PCNs
- Cephalosporins
- Tetracyclines
Which antibiotics can be given orally for a local effect?
- Aminoglycosides
2. Vancomycin
What does a STATIC antibiotic do?
Inhibits metabolic pathway
What does a CIDAL antibiotic do?
Kills organism directly by lysis
What is the best way to use multiple antibiotic therapy?
Use two drugs that act by different mechanisms!
The more different steps in an organism’s life cycle you can disrupt, the more likely you’ll be to kill it
What are two examples of synergism?
- Sulfonamide + trimethoprim = inhibit sequential steps in synthesis of folate
- PCNs + gentamicin (or streptomycin) = PCN inhibits the uptake of the other 1 and is used in treating enterococcal endocarditis
What pregnancy category do sulfonamides fall into?
B (is for bitches)
What drug can sulfas displace?
Warfarin from albumin
