WYAMYCIN S
Clinical safety rating: caution
Comprehensive clinical and safety monograph for WYAMYCIN S (WYAMYCIN S).
WYAMYCIN S (tetracycline) inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit, preventing the attachment of aminoacyl-tRNA to the mRNA-ribosome complex.
| Metabolism | Primarily metabolized in the liver via glucuronidation; minor metabolism by CYP450 isoenzymes. |
| Excretion | Renal (90-95% unchanged via glomerular filtration) and biliary (<5%). |
| Half-life | 2-3 hours in normal renal function; prolonged to 24-48 hours in end-stage renal disease. |
| Protein binding | 10-30% bound to serum proteins. |
| Volume of Distribution | 0.25-0.4 L/kg indicating primarily extracellular fluid distribution. |
| Bioavailability | IM: >90%. |
| Onset of Action | IM: 1-2 hours; IV: rapid (within 30 minutes). |
| Duration of Action | 6-8 hours (IM/IV) with dose adjustment needed in renal impairment. |
| Molecular Weight | The molecular weight of WYAMYCIN S (a combination of streptomycin and dihydrostreptomycin) is not defined for the mixture. For streptomycin sulfate, molecular weight is ~1457.4 Da; for dihydrostreptomycin sulfate, ~1461.5 Da. The formulation is a composite; typical aminoglycosides have molecular weights around 500-600 Da for the base. Assuming similar, approximate molecular weight is 581.58 Da (streptomycin base) and 583.6 Da (dihydrostreptomycin base). |
WYAMYCIN S (clarithromycin/sulfamethoxazole) is a fixed-dose combination. Adult: 1 tablet (500 mg clarithromycin/800 mg sulfamethoxazole) orally every 12 hours for 7-14 days.
| Dosage form | TABLET |
| Renal impairment | For CrCl 30-50 mL/min: reduce dose to 1 tablet every 24 hours. CrCl <30 mL/min: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B or C: use with caution, monitor for toxicity; no specific dose recommendation. |
| Pediatric use | Not recommended for children under 12 years due to sulfonamide safety concerns. |
| Geriatric use | Elderly patients may have age-related renal impairment; adjust dose based on CrCl. Monitor for QT prolongation and electrolyte disturbances. |
| 1st trimester | Aminoglycosides cross the placenta and may cause fetal harm. Use only if clearly needed and no alternative. Risk of ototoxicity and nephrotoxicity, but data limited. The drug should be avoided in first trimester unless benefit outweighs risk. |
| 2nd trimester | Potential for fetal ototoxicity and nephrotoxicity. Use only if necessary. Monitor drug levels and maternal renal function. |
| 3rd trimester | Risk of fetal ototoxicity and nephrotoxicity, especially with prolonged use. Avoid if possible. Short-term use may be considered if benefit outweighs risk. |
Clinical note
Comprehensive clinical and safety monograph for WYAMYCIN S (WYAMYCIN S).
| Placental transfer | Aminoglycosides cross the placenta. Fetal serum concentrations may reach 15-50% of maternal levels. Accumulation in fetal tissues, particularly kidney and inner ear, has been documented. |
| Breastfeeding | Aminoglycosides are excreted into breast milk in low concentrations. However, due to the potential for altered gut flora and direct effects on the infant (e.g., allergic reactions, ototoxicity, nephrotoxicity), caution is advised. Not recommended during breastfeeding unless no alternative. Monitor infant for diarrhea, rash, or hearing problems. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to aminoglycosidesMyasthenia gravisPre-existing severe renal impairment (unless dialysis available)Severe vestibular or cochlear impairmentConcurrent use with other ototoxic or nephrotoxic drugs (e.g., loop diuretics, vancomycin) is a relative contraindication but may be absolute in some contexts
| Precautions | Photosensitivity; hepatotoxicity especially in pregnancy or with pre-existing liver disease; renal dysfunction may require dose adjustment; use of outdated tetracycline may cause Fanconi syndrome; C. difficile-associated diarrhea; benign intracranial hypertension; tooth discoloration and bone growth retardation in fetuses/children under 8 years; concomitant use with isotretinoin may increase risk of pseudotumor cerebri. |
| Food/Dietary | No known food interactions with topical Wyamycin S. Systemic absorption is minimal, but avoid excessive intake of foods high in potassium if applied to large areas or compromised skin. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Avoid due to potential teratogenicity (aminoglycoside class). Second and third trimesters: Risk of fetal ototoxicity and nephrotoxicity; use only for life-threatening infections when no safer alternatives exist. |
| Fetal Monitoring | Monitor maternal renal function (serum creatinine, BUN, urinalysis), audiometry (hearing loss), and drug trough/peak levels. Fetal monitoring includes ultrasound for growth and amniotic fluid volume. |
| Fertility Effects | No documented adverse effects on fertility in humans; animal studies show no impairment at therapeutic doses. |
| Clinical Pearls | Wyamycin S (polymyxin B/bacitracin) is a topical triple-antibiotic ointment (with neomycin) primarily used for minor skin infections. Avoid use on large areas, deep wounds, or with compromised renal function due to systemic absorption risk. Monitor for hypersensitivity reactions, especially with neomycin component; cross-sensitivity with aminoglycosides is possible. Not effective against fungi or viruses. |
| Patient Advice | Apply a thin layer to clean, dry affected area 1-3 times daily. · Do not use on deep wounds, puncture wounds, or severe burns without medical advice. · Stop use and consult healthcare provider if rash, irritation, or infection worsens. · Avoid contact with eyes or mucous membranes. · Complete the full course as directed, even if symptoms improve. |