pharm of CNS infections Flashcards
What pharmokinetic parameter is most associated with a drug that will cross the BBB
Vd (volume of distribution)
What route of drug administration will reach the highest concentration in the CNS?
Intravenous (most common), CRIs
intrathecally (sub canal / subarachnoid space) is not practical
Ideal traits of a drug that will cross the BBB?
Lipophilic (higher diffusion & distribution abilities)
Protein-unbound and MW < 500 (higher diffusion ability)
Unionized (no charge -> higher distribution / lipophilicity)
What antibiotic drug classes are hydrophilic / won’t cross BBB?
Beta-lactams (cephalosporins & penicillins), aminoglycosides
Which tetracycline is the most lipophilic?
Minocyclines
(Doxy and oxy = most hydrophilic)
Initial antibiotic therapy for dog diagnosed with bacterial meningitis (seizures, pyrexia, rigid)? Describe antibiotic classes / spectrums, and route of administration. Benefits to using these drugs.
Unasyn and baytril
Unasyn = ampicillin & sulbactam (both beta-lactams) -> gram+ anaerobes
Baytril = enrofloxacin (floranquinolone) -> gram negatives, broad-spectrum
Both = bactericidal (rapidly kill bacteria); can give IV.
Both relatively lipophilic (within respective drug classes) -> broad-spectrum. Safe.
What bacteria cause bacterial meningitis?
diverse range of gram+, gram- & anaerobic species
What two factors greatly increase the effectiveness of an antibiotic crossing the BBB?
Safest, highest dose + intravenous administration
How come antibiotics’ efficacies decrease as CNS inflammation resolves?
BBB becomes more intact as inflammation resolves
Which drugs do not cross an intact BBB? Which do?
NSAIDs don’t
Steroids do! -> concern = immunosuppression!
4-year-old quarter horse male presents with asymmetric ataxia + muscle atrophy one day after returning from a show. Highest differential dx?
Equine Protozoal Myelitis / Myeloencephalitis
Which two antibacterial drug classes has activity against infectious agents and protozoa?
Potentiated sulfonamides & Nitromidazoles
Which drugs are used to treat EPM?
ponazurial or diclazuril; pyrimethamine/sulfadiazine
reach / cross the BBB -> effective at killing the protozoal parasites in the CNS
What strategy can be used to increase the concentrations of the drug used to treat EPM in the CNS?
administer a loading dose + with corn oil (latter is paste; increases solubility in stomach = increased absoprtion = more drug available to cross BBB)
2-year-old boer goat presents for suden onset of paraparesis & ataxia. dx? Tx?
Parelaphostrongylus tenius (meningeal worm)
Ivermectin tx
