R-P MYCIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for R-P MYCIN (R-P MYCIN).
R-P MYCIN is a macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome, specifically at the 23S rRNA of the peptidyl transferase center. This action blocks the translocation step, thereby preventing the elongation of the peptide chain.
| Metabolism | R-P MYCIN is primarily metabolized by the hepatic cytochrome P450 system, mainly via CYP3A4 isoenzyme. It undergoes demethylation and other oxidative processes. Significant first-pass metabolism occurs, leading to variable bioavailability. |
| Excretion | Renal (60-80% unchanged), biliary/fecal (15-20%). |
| Half-life | Terminal half-life 2-3 hours; prolonged in renal impairment (up to 6-8 hours in anuria). |
| Protein binding | 30-40% bound to serum albumin. |
| Volume of Distribution | 0.6-1.2 L/kg; increased in extracellular fluid expansion or decreased in dehydration. |
| Bioavailability | Oral: 30-40% (due to first-pass metabolism); IV: 100%. |
| Onset of Action | Oral: 1-2 hours; Intravenous: immediate (within minutes). |
| Duration of Action | 6-8 hours (oral); 8-12 hours (IV) depending on dose and infection site. |
Rifampin 600 mg orally once daily or 10 mg/kg intravenously once daily.
| Dosage form | TABLET, DELAYED RELEASE |
| Renal impairment | No dose adjustment required for GFR >30 mL/min. For GFR 10-30 mL/min, reduce dose to 300 mg orally once daily. For GFR <10 mL/min, administer 300 mg orally once daily with monitoring. |
| Liver impairment | Child-Pugh Class A: standard dosing. Child-Pugh Class B: reduce to 450 mg orally once daily. Child-Pugh Class C: reduce to 300 mg orally once daily or avoid use. |
| Pediatric use | Children: 10-20 mg/kg orally once daily, maximum 600 mg/day. For tuberculosis, 10-20 mg/kg orally once daily; for prophylaxis, 15-20 mg/kg orally once daily. |
| Geriatric use | No specific dose adjustment required, but monitor for hepatotoxicity and adjust based on renal function. Consider starting at lower end of dosing range due to age-related decline in organ function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for R-P MYCIN (R-P MYCIN).
| Breastfeeding | Not recommended during breastfeeding. M/P ratio unknown; potential for infant toxicity (e.g., nephrotoxicity, ototoxicity). |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: Avoid due to risk of fetal harm (e.g., skeletal dysplasia, cardiovascular malformations). Second/third trimester: Use only if benefit outweighs risk; may cause fetal renal impairment, oligohydramnios, and neonatal toxicity. |
| Fetal Monitoring |
■ FDA Black Box Warning
There is no FDA black box warning for R-P MYCIN.
| Serious Effects |
["Hypersensitivity to any macrolide antibiotic","Concomitant use with ergotamine or ergot alkaloids (risk of ergotism)","History of cholestatic jaundice or hepatic impairment associated with macrolide use","Preexisting QT interval prolongation or concurrent use of QT-prolonging agents"]
| Precautions | ["Potential for QT interval prolongation and risk of cardiac arrhythmias, especially in patients with pre-existing cardiac conditions or electrolyte imbalances","Risk of hepatotoxicity, including cholestatic hepatitis and hepatic necrosis","Possible exacerbation of myasthenia gravis","Increased risk of infantile hypertrophic pyloric stenosis in neonates exposed in utero or during breastfeeding","Drug interactions due to CYP3A4 inhibition, leading to increased levels of statins, warfarin, and other drugs","May cause false elevations in urinary catecholamines and certain liver enzymes"] |
Loading safety data…
| Baseline renal function (serum creatinine, BUN), audiometry, and hepatic panel. During therapy: weekly renal function, urine output, fetal ultrasound for oligohydramnios, and therapeutic drug monitoring of trough levels (target <2 µg/mL). |
| Fertility Effects | May impair fertility in males and females based on animal studies (testicular atrophy, reduced ovarian function). Human data limited; potential for reversible infertility. |