BIAXIN XL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BIAXIN XL (BIAXIN XL).
Clarithromycin is a macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, blocking peptide chain elongation.
| Metabolism | Primarily metabolized by the cytochrome P450 system, mainly CYP3A4, to active metabolites such as 14-hydroxyclarithromycin. |
| Excretion | Approximately 20-30% of the dose is excreted unchanged in urine, with the remainder as metabolites (primarily via biliary/fecal elimination). Renal clearance accounts for about 12% of total clearance. |
| Half-life | Terminal elimination half-life is 5-7 hours in healthy adults; prolonged to 20-40 hours in patients with severe hepatic impairment (Child-Pugh Class C). |
| Protein binding | Approximately 70% bound to plasma proteins, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Volume of distribution is 3-4 L/kg, indicating extensive tissue penetration (e.g., lungs, sinuses, tonsils). |
| Bioavailability | Oral bioavailability is approximately 50% due to first-pass metabolism; food does not significantly affect the extended-release formulation. |
| Onset of Action | Oral: 1-2 hours for detectable serum concentrations; clinical effect typically within 24 hours. |
| Duration of Action | Duration approximately 12 hours based on dosing interval of every 12 hours for immediate-release; BIAXIN XL maintains therapeutic concentrations over 24 hours with once-daily dosing. |
500 mg orally once daily for 7 to 14 days
| Dosage form | TABLET |
| Renal impairment | CrCl <30 mL/min: 500 mg orally once daily or 250 mg twice daily. CrCl <30 mL/min not recommended for BIAXIN XL due to decreased clearance. |
| Liver impairment | Child-Pugh Class C: reduce dose by 50% or consider alternative therapy. Child-Pugh Class A or B: no adjustment necessary. |
| Pediatric use | Not approved for use in children less than 12 years of age. For children ≥12 years: same as adult dosing. |
| Geriatric use | Increased risk of QT prolongation. Monitor renal function and consider dose adjustment based on creatinine clearance. No specific dose adjustment is recommended solely for age. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BIAXIN XL (BIAXIN XL).
| Breastfeeding | Clarithromycin is excreted into breast milk. M/P ratio is approximately 1.0 (based on total drug). Consider the potential for infant gastrointestinal effects (diarrhea, candidiasis) and theoretical risk of antibiotic-associated colitis. Compatible with breastfeeding with monitoring for adverse effects in the infant. |
| Teratogenic Risk | Pregnancy Category C. First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses, but maternal toxicity at high doses produced fetal malformations. Second and third trimesters: No known fetal risks from limited human studies; however, due to rare reports of pyloric stenosis in infants exposed to macrolides late in pregnancy, consider risk-benefit. Overall, use only if clearly needed. |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
["Hypersensitivity to clarithromycin, erythromycin, or any macrolide antibiotic","Concomitant use with ergotamine or dihydroergotamine","Concomitant use with HMG-CoA reductase inhibitors that are extensively metabolized by CYP3A4 (e.g., lovastatin, simvastatin)","Concomitant use with pimozide","History of cholestatic jaundice or hepatic dysfunction associated with prior clarithromycin use","QTc prolongation or cardiac arrhythmia history (relative contraindication)"]
| Precautions | ["Increased risk of cardiac arrhythmias (QT prolongation, torsades de pointes) in patients with pre-existing cardiac conditions or electrolyte abnormalities","Hepatotoxicity, including hepatic failure and jaundice","Exacerbation of myasthenia gravis symptoms","Increased risk of colchicine toxicity when used with P-glycoprotein inhibitors","Potential for drug interactions due to CYP3A4 inhibition"] |
| Food/Dietary | Take with food to enhance absorption and reduce GI intolerance. Avoid grapefruit and grapefruit juice as they may alter drug metabolism. No other significant food interactions. |
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| Fetal Monitoring | Monitor liver function tests (LFTs) due to potential hepatotoxicity; auditory function in neonates if prolonged maternal use; signs of infant pyloric stenosis if used near term. Monitor for maternal QT prolongation if other risk factors present. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies showed no impairment of fertility at clinically relevant doses. |
| Clinical Pearls | BIAXIN XL (clarithromycin extended-release) is a macrolide antibiotic with a long half-life allowing once-daily dosing. It is a strong CYP3A4 inhibitor, increasing levels of many drugs including statins, warfarin, and oral contraceptives. Prolongs QT interval; avoid in patients with known QTc prolongation or concurrent use of other QT-prolonging agents. Common adverse effects include metallic taste and gastrointestinal upset. Monitor liver function in hepatic impairment. |
| Patient Advice | Take with food to reduce stomach upset. · Do not crush or chew the tablet; swallow whole. · Complete the full course even if you feel better. · Avoid alcohol during treatment. · Inform your doctor about all medications, including OTC and herbal supplements, due to drug interactions. · Report symptoms of arrhythmia (dizziness, palpitations, fainting) or severe diarrhea. · May cause metallic taste; this is temporary. · Use alternate contraception if on oral contraceptives due to interaction. |