ROBITET
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ROBITET (ROBITET).
Robitussin (Robitet) is a combination product containing the antitussive dextromethorphan and the expectorant guaifenesin. Dextromethorphan acts centrally on the cough center in the medulla oblongata by increasing the threshold for coughing, primarily through sigma-1 receptor agonism and NMDA receptor antagonism. Guaifenesin increases the hydration of respiratory tract secretions, reducing mucus viscosity and facilitating expectoration.
| Metabolism | Dextromethorphan is primarily metabolized by CYP2D6 to dextrorphan (active metabolite) and other metabolites; undergoes O-demethylation and N-demethylation. Guaifenesin is extensively metabolized via oxidation and conjugation, primarily to beta-(2-methoxyphenoxy)-lactic acid and other metabolites. |
| Excretion | Renal: 30% unchanged; biliary/fecal: 50% as metabolites; remainder metabolized |
| Half-life | Terminal elimination half-life: 3.5 hours (2.6–4.8 h) in adults; prolonged to 6–12 h in severe renal impairment |
| Protein binding | 92–96% bound to albumin and alpha-1-acid glycoprotein |
| Volume of Distribution | Vd = 0.6–0.8 L/kg, indicating moderate tissue distribution and extensive extravascular penetration |
| Bioavailability | Oral: 85–95% (first-pass effect <10%) |
| Onset of Action | Oral: 30–60 minutes; IV: 5–10 minutes; IM: 15–30 minutes |
| Duration of Action | Oral single dose: 6–8 hours; IV bolus: 4–6 hours; sustained-release forms: up to 12 hours |
Tetracycline hydrochloride: 250-500 mg orally every 6 hours; maximum 4 g/day.
| Dosage form | CAPSULE |
| Renal impairment | CrCl 50-80 mL/min: 250 mg every 8-12 hours; CrCl 10-50 mL/min: 250 mg every 12-24 hours; CrCl <10 mL/min: 250 mg every 24 hours or avoid use. |
| Liver impairment | Child-Pugh Class A: no adjustment; Class B: reduce dose by 50%; Class C: avoid use. |
| Pediatric use | Children ≥8 years: 25-50 mg/kg/day orally divided every 6 hours; maximum 3 g/day. |
| Geriatric use | Reduce dose by 50% or extend interval; monitor renal function and avoid if CrCl <30 mL/min. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ROBITET (ROBITET).
| Breastfeeding | Tetracyclines are excreted in breast milk with M/P ratio approximately 0.2-0.4. Not recommended due to potential for bone and tooth effects in infants. Consider alternative therapy. |
| Teratogenic Risk | ROBITET is not recommended during pregnancy as tetracyclines may cause fetal harm. First trimester: no increased risk of major malformations in human data, but animal studies show embryo-fetal toxicity. Second and third trimesters: risk of permanent tooth discoloration and enamel hypoplasia, and inhibition of bone growth. Avoid use after week 16. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to any component; concurrent use or within 14 days of MAO inhibitors; patients with poorly controlled asthma or chronic bronchitis; history of drug abuse (dextromethorphan).
| Precautions | Do not use for persistent or chronic cough (e.g., with smoking, asthma, emphysema). Avoid taking with MAOIs or for 2 weeks after stopping MAOIs; may cause serotonin syndrome. Use caution in patients with liver disease, renal impairment, or severe respiratory conditions. Dextromethorphan can cause dizziness, sedation, and abuse potential at high doses. Guaifenesin can cause urticaria or gastrointestinal upset. |
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| Fetal Monitoring |
| Monitor maternal hepatic and renal function. In fetus, monitor for bone growth and dental development if exposure occurs. Assess for opportunistic infections due to possible immunosuppression. |
| Fertility Effects | Tetracyclines may affect spermatogenesis and fertility in males; effects are reversible. In females, no significant impact on fertility reported. |