Musculoskeletal/Joint pharmacology: antibiotics

Question 1

What should be the AB treatment protocol for osteomyelitis, septic arthritis, and tenosynovitis

Answer 1

-Acute infection: ideally parenteral ABs, high doses for more than 3 weeks with bacteriocidal ABs
-Note: articular cartilage is avascular and alymphatic so difficult for systemically administered drug to reach

Question 2

What ABs should be chosen for osteomyelitis, septic arthritis, and tenosynovitis

Answer 2

-For infection caused by beta-lactamase producing staph: Cephalosporins, clindamycin, or amoxycillin-clavulanate
-In small animals: clindamycin and metronidazole for anaerobic infections

Question 3

What do non-systemic AB drug delivery systems provide and what methods can they be used

Answer 3

-Can provide sustained high local drug concentrations while minimizing systemic toxicity
-Methods include local injection and regional limb perfusion either by IV or IO routes, biodegradable or non-biodegradable implants, or CRI/in dwelling catheter

Question 4

What are the benefits of intra-articular injections and what drugs are most used

Answer 4

-Benefits: high synovial fluid and bone concentrations with low doses, single injection will result in synovial concentrations above MIC for more than 24 hours
-Drugs used: gentamicin, amikacin, ceftiocur (neeed to be non-irritating preps)

Question 5

When is regional limb perfusion used, how is it done, and which drugs are commonly used

Answer 5

-When: used for treating distal limb infection
-How: tourniquet proximal to target area with injection IV (cephalon, saphenous, and palmar digital veins)
-Drugs: aminoglycosides (amikacin and gentamicin) most commonly used

Question 6

What are the advantages and disadvantages of regional limb perfusion

Answer 6

-Advantages: reaches infected tissue/joints by diffusion, far greater concentration (>10 fold) than with systemic IV treatment, concentrations remain higher in affected region for longer than with systemic IV treatment
-Disadvantages: may not work if tourniquet incorrectly applied, risk of venous thrombosis, difficult to perform in a limb with cellulitis

Question 7

What is the difference between non-biodegradable and biodegradable implants

Answer 7

Non-biodegradable implants release drugs for months and need to be removed as they are not broken down. Biodegradable implants are broken down so they do not need to be removed, but they only release for weeks

Question 8

What biodegradable implants are available

Answer 8

-Collagen sponges: gentamicin impregnated collagen sponges, delivery for about 2 weeks, expensive and can cause hypersensitivity related reaction
-Plaster of Paris: liquid ABs (gentamicin, amikacin) molded into beads and sterilized before use, inexpensive