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. |
| Molecular Weight | 747.95 |
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 | Use only if clearly needed; no evidence of major malformations from human studies but caution advised due to limited data. |
| 2nd trimester | Safe with caution; no known increased risk of adverse fetal outcomes. |
| 3rd trimester | Avoid near term due to risk of infantile hypertrophic pyloric stenosis following postnatal exposure. |
Clinical note
Comprehensive clinical and safety monograph for BIAXIN XL (BIAXIN XL).
| Placental transfer | Crosses placenta; fetal serum levels approximately 1-10% of maternal concentrations. |
| Breastfeeding | Small amounts excreted into breast milk; not expected to cause adverse effects in term infants but caution with preterm or G6PD-deficient infants. Monitor for diarrhea and candidiasis. |
| Lactation Rating |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Hypersensitivity to clarithromycin or any macrolide antibioticConcurrent use with ergotamine or dihydroergotamineConcurrent use with cisapride, pimozide, astemizole, terfenadine (risk of QT prolongation)Concurrent use with HMG-CoA reductase inhibitors (statins) extensively metabolized by CYP3A4 (e.g., lovastatin, simvastatin)Concurrent use with colchicine in patients with hepatic or renal impairment
| 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. |
Loading safety data…
| L2 (or 'Safe' depending on system) |
| 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. |
| 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. |