Editing Ciprofloxacin (section)

==Pharmacokinetics==
Ciprofloxacin for systemic administration is available as immediate-release tablets, extended-release tablets, an oral suspension, and as a solution for intravenous administration. When administered over one hour as an intravenous infusion,<ref name="Cipro FDA label" /> ciprofloxacin rapidly distributes into the tissues, with levels in some tissues exceeding those in the serum. Penetration into the central nervous system is relatively modest, with cerebrospinal fluid levels normally less than 10% of peak serum concentrations. The serum half-life of ciprofloxacin is about 4–6 hours, with 50–70% of an administered dose being excreted in the urine as unmetabolized drug. An additional 10% is excreted in urine as metabolites. Urinary excretion is virtually complete 24 hours after administration. Dose adjustment is required in the elderly and in those with renal impairment.<ref name="Cipro FDA label" />

Ciprofloxacin is weakly bound to serum proteins (20–40%). It is an inhibitor of the drug-metabolizing enzyme [[CYP1A2|cytochrome P450 1A2]], which leads to the potential for clinically important drug interactions with drugs metabolized by that enzyme.<ref name=AHFS2015 /> Ciprofloxacin is about 70% available when administered orally.<ref name="Cipro FDA label" />

The extended release tablets<ref>{{cite web |url=http://www.accessdata.fda.gov/drugsatfda_docs/label/2003/21554_ciproXR_lbl.pdf |title=Cipro XR Prescribing Information |publisher=U.S. [[Food and Drug Administration]] (FDA) |url-status=live |archive-url=https://web.archive.org/web/20131230232923/http://www.accessdata.fda.gov/drugsatfda_docs/label/2003/21554_ciproXR_lbl.pdf |archive-date=30 December 2013}}</ref> allow once-daily administration by releasing the drug more slowly in the gastrointestinal tract. These tablets contain 35% of the administered dose in an immediate-release form and 65% in a slow-release matrix. Maximum serum concentrations are achieved between 1 and 4 hours after administration. Compared to the 250- and 500-mg immediate-release tablets, the 500-mg and 1000-mg XR tablets provide higher C<sub>max</sub>, but the 24‑hour AUCs are equivalent.

Ciprofloxacin immediate-release tablets contain ciprofloxacin as the hydrochloride salt, and the XR tablets contain a mixture of the hydrochloride salt and the free base.<ref name="Cipro FDA label" />