Tissue penetration of antimicrobials

Summary

Class	Antimicrobial	Blood	CNS	Vitreous	Urine	Prostate	Necrotic
Antibiotics: β-Lactams
Penicillins	β-lactamase inhibitors		–
	ampicillin		+				–
	piperacillin-tazobactam					+†
Cephalosporins	first-generation cephalosporins		–				–
	second-generation cephalosporins		–
	third-generation cephalosporins					+†
	cefepime						+
	ceftazidime		+				+
Cephamycins	cephamycins		–
	cefoxitin						–
Carbapenems	imipenem						+
Antibiotics: Non-β-Lactams
Aminoglycosides							–
Chloramphenicol	chloramphenicol						+
Fluoroquinolones			–?			+	+
Fosfomycin	fosfomycin					+
Lincosamides	clindamycin		–				+
Lipopeptides	daptomycin	+	–		+
Macrolides	macrolides		–			+
Nitrofurans	nitrofurantoin	–	–		+	–	–
Nitroimidazoles	metronidazole						+
Rifamycins	rifampin					+
Sulfonamides	trimethoprim-sulfamethoxazole					+
Tetracyclines	tetracyclines		–			+
	doxycycline					+	+
Antivirals
	acyclovir / valacyclovir			+
	ganciclovir			+
	foscarnet
Antifungals
Azoles	fluconazole						+
Echinocandins		+			–
Class	Antimicrobial	Blood	CNS		Urine	Prostate	Necrotic

• † if inflammation present

Specific Tissues

Prostate

• Poorly penetrated by most antibiotics
• Penetration is higher with a high concentration gradient, high lipid solubility, low degree of ionization, high dissociation constant, low protein binding, and small molecular size
• Fluoroquinolones are the mainstay of therapy, though there is increasing resistance
• TMP-SMX often used, though conflicting data about its penetration into the prostate
• Minocycline, doxycycline, and macrolides achieve high levels in the prostate but are rarely indicated for the causative organisms
• Third-generation cephalosporins and carbapenems can be used
• Piperacillin, aztreonam, imipenem, and some aminoglycosides are likely useful

Bone

• Essentially all antibiotics achieve similar bone-to-serum levels, with the exception of oral β-lactams which nevertheless have no worse outcomes1

Eye

• Ocular compartments include anterior and posterior
  • Anterior includes aqeous humour, and is best accessed using topical medications
  • Posterior includes vitreous humour, retina, and choroid, and is best accessed using intravitreal or systemic medications
• Penetration of systemic antimicrobials into retina and vitreous is poor (~0 to 2%), but is better with inflammation2

Class	Antimicrobial	Vitreal Penetration
penicillins	ampicillin	below MIC in non-inflamed rabbit eyes
	amoxicillin	2% (below MIC) in non-inflamed rabbit eyes
	piperacillin	undetectable in inflamed human eyes
cephalosporins	cefazolin	above MIC in inflamed rabbit eyes
	ceftriaxone	4% in non-inflamed human eyes
	ceftazidime	30% in inflamed rabbit eyes
	cefipime	8% in non-inflamed human eyes
carbapenems	imipenem	8 to 10% in non-inflamed human eyes
	meropenem	30% in non-inflamed human eyes
oxazolidinones	linezolid	30 to 80% in non-inflamed human eyes
	vancomycin	above MIC in inflamed rabbit eyes
	daptomycin	30% in inflamed human eyes
aminoglycosides	amikacin	below MIC in inflamed rabbit eyes
	gentamicin	below MIC in inflamed rabbit eyes
fluoroquinolones	ciprofloxacin	below MIC in non-inflamed human eyes
	levofloxacin	30% but below MIC in non-inflamed human eyes
	moxifloxacin	10 to 40% and above MIC in non-inflamed human eyes