Gatifloxacin promotes breakage of double-stranded DNA in susceptible organisms and inhibits DNA gyrase, which is essential in reproduction of bacterial DNA.

Absorption
Absorbed readily form the GI tract (oral); peak plasma concentrations after 1-2 hours. Bioavailability: 96%.

Distribution
Widely distributed into body tissues. Protein-binding: 20%.

Metabolism
Limited metabolism.

Excretion
Via the urine (as unchanged and 1% metabolite); via the faeces (5% as unchanged). Limited metabolism; 7-14 hours (elimination half-life).

Rapid heartbeat, mental confusion, hallucinations, agitation, nightmares, depression; photophobia; tendon rupture; headache, dizziness, insomnia, chills, fever; back pain, abdominal pain; constipation, nausea, vomiting, diarrhoea, inflammation of the tongue, mouth sores; abnormal vision, ringing in the ears, vaginitis.

Potentially Fatal: Hyperosmolar nonketotic hyperglycaemic coma, diabetic ketoacidosis, hypoglycaemic coma, convulsions and mental status changes.

Monitor
Ocular adverse reactions
Monitor patient for signs and symptoms of ocular adverse reactions (eg, burning, stinging pain, irritation) and improvement in conjunctivitis. Notify health care provider if conjunctivitis is not improving or is worsening or if intolerable adverse reactions occur.

May prolong QT interval; uncorrected hypokalaemia; known or suspected CNS disorders, renal and hepatic impairment. Elderly.

Antacids, ferrous salts, bismuth subsalicylate, sucralfate and zinc salts reduce bioavailability of gatifloxacin. May increase digoxin plasma levels. Probenecid, cimetidine and loop diuretics increase gatifloxacin levels. NSAIDs may increase the risk of CNS stimulation and convulsions. Concurrent use of bepridil, cisapride, erythromycin, pentamidine, phenothiazines, or TCAs may prolong QT interval. Concurrent corticosteroid therapy may increase the risk of tendon rupture. Increased risk of hypoglycaemia when used with oral antidiabetic agents. May enhance hypoprothrombinaemic effects of oral anticoagulants.

Potentially Fatal: Increased risk of adverse CV reactions when used with class IA or III antiarrhythmics e.g. disopyramide and amiodarone.

Oral
Respiratory tract infections
Adult: 400 mg once daily.

Renal impairment: Patients on haemodialysis or continuous peritoneal dialysis: Initially, 400 mg/day. Maintenance dose: 200 mg daily.
CrCl (ml/min)    Dosage Recommendation
<40                  Initially, 400 mg/day. Maintenance dose: 200 mg daily.

Oral
Urinary tract infections
Adult: 400 mg once daily.

Renal impairment: Patients on haemodialysis or continuous peritoneal dialysis: Initially, 400 mg/day. Maintenance dose: 200 mg daily.
CrCl (ml/min)    Dosage Recommendation
<40                  Initially, 400 mg/day. Maintenance dose: 200 mg daily.

Oral
Susceptible infections
Adult: 400 mg once daily.

Renal impairment: Patients on haemodialysis or continuous peritoneal dialysis: Initially, 400 mg/day. Maintenance dose: 200 mg daily.
CrCl (ml/min)    Dosage Recommendation
<40                  Initially, 400 mg/day. Maintenance dose: 200 mg daily.

Oral
Uncomplicated gonorrhoea
Adult: 400 mg as a single dose.

Oral
Uncomplicated urinary tract infections
Adult: 400 mg as a single dose or 200 mg daily for 3 days.

Renal impairment: Patients on haemodialysis or continuous peritoneal dialysis: Initially, 400 mg/day. Maintenance dose: 200 mg daily.
CrCl (ml/min)    Dosage Recommendation
<40                  Initially, 400 mg/day. Maintenance dose: 200 mg daily.

Intravenous
Respiratory tract infections
Adult: 400 mg once daily, infused as a 2 mg/ml solution over 60 minutes.

Renal impairment: Patients on haemodialysis or continuous peritoneal dialysis: Initially, 400 mg/day. Maintenance dose: 200 mg daily.
CrCl (ml/min)    Dosage Recommendation
<40                  Initially, 400 mg/day. Maintenance dose: 200 mg daily.

Intravenous
Urinary tract infections
Adult: 400 mg once daily, infused as a 2 mg/ml solution over 60 minutes.

Renal impairment: Patients on haemodialysis or continuous peritoneal dialysis: Initially, 400 mg/day. Maintenance dose: 200 mg daily.
CrCl (ml/min)    Dosage Recommendation
<40                  Initially, 400 mg/day. Maintenance dose: 200 mg daily.

Intravenous
Susceptible infections
Adult: 400 mg once daily, infused as a 2 mg/ml solution over 60 minutes.

Renal impairment: Patients on haemodialysis or continuous peritoneal dialysis: Initially, 400 mg/day. Maintenance dose: 200 mg daily.
CrCl (ml/min)    Dosage Recommendation
<40                  Initially, 400 mg/day. Maintenance dose: 200 mg daily.

Ophthalmic
Conjunctivitis
Adult: As a 0.3% solution: Instill 1 drop 2 hourly into affected eye(s) up to 8 times daily for the 1st 2 days, then reduce to 1 drop 4 times daily on days 3-7.

Contraindicated in pregnancy

 Contraindicated in lactation

PO/IV
Safety and efficacy not established in patients younger than 18 years of age.

Ophthalmic
Safety and efficacy not established in patients younger than 1 years of age.

Hypersensitivity; children <18 years; concurrent use of class IA or III antiarrhythmics, QT-prolongation drugs; diabetics; pregnancy, lactation.

Intravenous
Store at 25°C.

Ophthalmic
Store at 15-25°C.

Oral
Store at 25°C.