BIAXIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BIAXIN (BIAXIN).
Binds to the 50S ribosomal subunit, inhibiting bacterial protein synthesis by blocking peptide chain elongation.
| Metabolism | Primarily metabolized by CYP3A4 isoenzyme; clarithromycin undergoes first-pass metabolism to form 14-hydroxyclarithromycin (active metabolite). |
| Excretion | Approximately 20-30% of administered dose is excreted unchanged in urine; remainder is hepatically metabolized and excreted in bile and feces (~50% fecal elimination). |
| Half-life | Terminal elimination half-life: 3-7 hours (single dose, 250-500 mg); with multiple dosing, half-life may extend to 7-10 hours due to saturable metabolism. Clinical context: Shorter half-life requires twice-daily dosing; extended half-life (via 14-hydroxy metabolite, t1/2 ~11 h) contributes to antibacterial activity. |
| Protein binding | 65-75% bound, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd: 2.6-3.5 L/kg. Clinical meaning: Large Vd indicates extensive tissue penetration, including lungs, tonsils, and sinuses, exceeding serum concentrations. |
| Bioavailability | Oral bioavailability: 50-55% (250 mg tablet); may be increased to 60-70% when administered with food. Intravenous: 100%. |
| Onset of Action | Oral: Onset of bacteriostatic activity occurs within 1-4 hours after administration, corresponding to peak serum concentrations. Intravenous: Immediate clinical effect upon infusion completion. |
| Duration of Action | Duration of antibacterial effect: 12 hours, supporting twice-daily dosing. Clinical notes: Post-antibiotic effect (PAE) of 3-7 hours against susceptible organisms prolongs suppression of bacterial growth after serum levels decline. |
| Molecular Weight | 747.96 |
250-500 mg orally every 12 hours for 7-14 days; extended-release: 1000 mg orally every 24 hours for 7-14 days
| Dosage form | FOR SUSPENSION |
| Renal impairment | CrCl <30 mL/min: reduce dose by 50%; CrCl <10 mL/min: not recommended; no adjustment for CrCl >30 mL/min |
| Liver impairment | Child-Pugh Class C: reduce dose by 50% or consider alternative; mild to moderate hepatic impairment: no adjustment |
| Pediatric use | 15 mg/kg/day orally divided every 12 hours; maximum 500 mg/day for 10 days; for extended-release, not recommended for children <12 years |
| Geriatric use | No specific dose adjustment; monitor renal function and adjust per renal guidelines; increased risk of QT prolongation |
| 1st trimester | Clarithromycin (Biaxin) should be used during the first trimester only if clearly needed. Animal studies have shown embryotoxicity at high doses; however, human data are limited. Risk cannot be ruled out. |
| 2nd trimester | Clarithromycin crosses the placenta and has been associated with increased risk of spontaneous abortion and cardiovascular malformations in some epidemiological studies. Use only if benefit outweighs potential risk. |
| 3rd trimester | Use in the third trimester is generally avoided unless no alternative, as it may increase risk of infantile hypertrophic pyloric stenosis (IHPS) if used near term or during lactation. |
Clinical note
Comprehensive clinical and safety monograph for BIAXIN (BIAXIN).
| Placental transfer | Clarithromycin readily crosses the placenta with fetal serum concentrations reaching 15-40% of maternal serum levels. |
| Breastfeeding | Clarithromycin is excreted into breast milk in small amounts. The relative infant dose is estimated to be 1-2% of the maternal weight-adjusted dose. Monitor the infant for gastrointestinal disturbances (e.g., diarrhea, loose stools) or rash. Avoid use in breastfeeding mothers of infants with hepatic or renal impairment. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to clarithromycin, erythromycin, or any macrolide antibioticConcurrent use with cisapride, pimozide, astemizole, terfenadine, ergotamine, dihydroergotamine, or HMG-CoA reductase inhibitors (statins) extensively metabolized by CYP3A4 (e.g., lovastatin, simvastatin)History of cholestatic jaundice/hepatic dysfunction associated with prior clarithromycin useProlonged QT interval or concurrent use with drugs that prolong QT interval
| Precautions | Increased risk of cardiac arrhythmias, including QT prolongation and torsades de pointes; avoid in patients with known QT prolongation or concurrent use with QT-prolonging drugs., Potential for hepatotoxicity (elevated liver enzymes, hepatitis); monitor liver function., Exacerbation of myasthenia gravis symptoms., Clostridioides difficile-associated diarrhea (CDAD)., Drug interactions via CYP3A4 inhibition (e.g., statins, warfarin, colchicine, and other macrolides)., Pregnancy Category C; avoid use unless no alternative (clarithromycin associated with increased risk of miscarriage and fetal abnormalities in animal studies). |
| Food/Dietary |
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| Lactation Rating | L2 (Limited data - probably compatible) |
| Teratogenic Risk | FDA Pregnancy Category C. Animal studies have shown fetal harm (cleft palate, skeletal abnormalities) at doses 2-5 times the human clinical dose. No adequate human studies. First trimester: Avoid unless benefit justifies risk. Second and third trimesters: Limited data; use only if clearly needed. Monitor for potential maternal hepatotoxicity. |
| Fetal Monitoring | Monitor liver function tests (AST, ALT) and renal function in pregnant women receiving prolonged therapy. Assess for maternal gastrointestinal symptoms (e.g., pseudomembranous colitis). In neonates, monitor for signs of pyloric stenosis if breastfeeding. No specific fetal monitoring required but consider growth ultrasonography if used during first trimester. |
| Fertility Effects | Animal studies have shown no significant adverse effects on fertility at clinically relevant doses. In humans, clarithromycin is not known to impair male or female fertility. However, as with any antibiotic, disruption of the gut microbiome may theoretically affect hormonal regulation, but no direct evidence of fertility reduction exists. |
| Grapefruit and grapefruit juice should be avoided as they inhibit CYP3A4 and may increase clarithromycin levels, raising risk of QT prolongation. High-fat meals may delay absorption but do not significantly alter total exposure. Alcohol is not specifically contraindicated but may increase gastrointestinal irritation; avoid concurrent use of statins (especially simvastatin, lovastatin) due to increased myopathy risk. |
| Clinical Pearls | Biaxin (clarithromycin) is a macrolide antibiotic with activity against atypical pathogens (e.g., Legionella, Mycoplasma, Chlamydia). It is a potent CYP3A4 inhibitor, increasing levels of statins, warfarin, and colchicine. Use caution in myasthenia gravis; may exacerbate weakness. QT prolongation risk: avoid use with other QT-prolonging drugs, correct electrolyte abnormalities. For H. pylori eradication, combine with amoxicillin and a PPI as first-line. Renal dose adjustment required for CrCl <30 mL/min. |
| Patient Advice | Take with or without food, but taking with food may reduce stomach upset. · Complete the full course even if you feel better to prevent resistance. · Avoid grapefruit or grapefruit juice while on this medication. · Report any signs of liver problems: yellowing of skin/eyes, dark urine, severe nausea/vomiting. · May cause metallic or bitter taste in the mouth; this is usually temporary. · Tell your doctor if you have myasthenia gravis, as clarithromycin can worsen symptoms. · Avoid driving or operating heavy machinery if you experience dizziness or vision changes. · Use effective contraception if applicable; clarithromycin may reduce oral contraceptive efficacy. |