Rifaximin

XIFAXAN

What it isMinimally absorbed RNA-polymerase-inhibiting rifamycin; hepatic encephalopathy, IBS with diarrhea, and travelers' diarrhea.

Why this oneIt acts almost entirely in the gut, avoiding the systemic toxicity and enzyme induction associated with rifampin.

What limits itCost is the main barrier. For hepatic encephalopathy it is generally added to lactulose rather than replacing it.

FDA-approved for

FDA dosing	Population	Start	Target	Max
Travelers' diarrhea (noninvasive E. coli)	adults & ≥12 yr	200 mg TID x3 days	200 mg TID x3 days	200 mg TID x3 days
Hepatic encephalopathy (recurrence reduction)	adult	550 mg BID	550 mg BID	550 mg BID
Irritable bowel syndrome with diarrhea (IBS-D)	adult	550 mg TID x14 days	550 mg TID x14 days	550 mg TID x14 days

Renal Undefined (not studied)

Hepatic No dosage adjustment recommended; use with caution in severe (Child-Pugh C)

IBS-D: recurrence may be retreated up to two times with the same regimen

Not effective for travelers' diarrhea with fever/bloody stool or non-E. coli pathogens; discontinue if symptoms worsen or persist >24-48 h
C. difficile-associated diarrhea
Caution in severe (Child-Pugh C) hepatic impairment (increased exposure)
P-glycoprotein inhibitors (e.g., cyclosporine) substantially increase systemic exposure
Severe cutaneous adverse reactions (SJS, TEN) in cirrhosis

Pregnancy No human data; teratogenic in animals — advise of potential fetal risk

Lactation Undefined

NO BOXED WARNINGS

Principal riskLittle; minimal absorption

Cost, est. cash$200–$1,500/month

Generic entry2029 est.

Therapeutic safety burden1 / 4

Overdose danger0 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk0 / 4

Legacy pregnancy categoryC

Defining liabilityLocal irritation or hypersensitivity; systemic toxicity is minimal with correct local use.

no kinetic interactions