QUIBRON-T/SR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for QUIBRON-T/SR (QUIBRON-T/SR).
Theophylline is a methylxanthine that relaxes bronchial smooth muscle by inhibiting phosphodiesterase, increasing intracellular cAMP, and antagonizing adenosine receptors.
| Metabolism | Hepatic via CYP1A2, CYP2E1, and CYP3A4; undergoes N-demethylation and oxidation. Saturable kinetics. |
| Excretion | Renal: ~10% unchanged; Hepatic metabolism (CYP1A2, CYP3A4): 90% to inactive metabolites (1,3-dimethyluric acid, 3-methylxanthine, 1-methyluric acid). Biliary/fecal: minimal (<5%). |
| Half-life | Terminal t1/2: 3-12 hours (adults); 1-9 hours (children); prolonged in cirrhosis (up to 30 hours), heart failure, elderly. Clinical context: Narrow therapeutic index (5-15 mcg/mL); dosing interval adjusted based on t1/2. |
| Protein binding | ~40% bound to albumin. Binding is reversible and non-saturable. |
| Volume of Distribution | Vd: 0.3-0.7 L/kg (adults); approximates total body water. Increased Vd in premature infants and obesity; decreased in dehydration. |
| Bioavailability | Oral: 100% (immediate-release); 90-100% for SR formulations (dose-dependent slightly lower). |
| Onset of Action | Oral immediate-release: 30-60 min; Oral sustained-release (SR): 1-2 hours. Peak effect: immediate-release 1-2 hours; SR 4-6 hours. |
| Duration of Action | Immediate-release: 4-6 hours; SR: 8-12 hours (dosing every 8-12 hours). Note: Sustained-release maintains therapeutic levels for bronchodilation. |
200-400 mg orally every 12 hours; extended-release tablets. Initial dose 200 mg every 12 hours; may increase by 200 mg daily every 3-7 days based on serum theophylline levels (target 5-15 mcg/mL). Maximum 800 mg/day.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | GFR >50 mL/min: no adjustment. GFR 10-50 mL/min: use 75% of normal dose, monitor levels. GFR <10 mL/min: use 50% of normal dose, monitor levels. Dose frequency unchanged. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%, monitor levels. Child-Pugh C: reduce dose by 70%, monitor levels. Use immediate-release forms preferred. |
| Pediatric use | 6-12 years: 10-16 mg/kg/day in divided doses every 12 hours (extended-release). 12-16 years: 12-18 mg/kg/day; target serum theophylline 5-15 mcg/mL. Maximum 800 mg/day. |
| Geriatric use | Initiate at lower end of dosing (200-400 mg/day). Monitor serum concentrations due to decreased clearance. Avoid doses >400 mg/day without level monitoring. Titrate cautiously. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for QUIBRON-T/SR (QUIBRON-T/SR).
| Breastfeeding | Theophylline is excreted into breast milk with M/P ratio approximately 0.6-0.7. Relative infant dose is less than 10% of maternal weight-adjusted dose. Considered compatible with breastfeeding, but monitor infant for irritability or insomnia. Use lowest effective maternal dose. |
| Teratogenic Risk | Theophylline (active ingredient) is not teratogenic in humans. First trimester: No increased risk of major malformations from epidemiological studies. Second/third trimester: No specific fetal risks; however, high maternal serum levels may cause neonatal toxicity (jitteriness, tachycardia) if near term. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Hypersensitivity to theophylline or any component","History of seizure disorder (relative)","Active peptic ulcer disease (relative)"]
| Precautions | ["Seizures may occur at therapeutic levels","Use caution in patients with peptic ulcer, seizure disorders, cardiac arrhythmias","Monitor serum theophylline levels to avoid toxicity","Drug interactions with fluoroquinolones, cimetidine, macrolides, and allopurinol"] |
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| Fetal Monitoring | Monitor maternal serum theophylline levels (target 5-15 mcg/mL), respiratory status, and heart rate. Fetal monitoring includes nonstress test or biophysical profile if maternal condition unstable. Assess neonatal heart rate and respiratory pattern after delivery if mother received near term. |
| Fertility Effects | No known adverse effects on fertility in males or females based on available data. Theophylline does not impair reproductive function in animal studies. |