ASBRON
Clinical safety rating
cautionComprehensive clinical and safety monograph for ASBRON (ASBRON).
Asbron is a combination product containing theophylline and guaifenesin. Theophylline is a methylxanthine that inhibits phosphodiesterase, leading to increased intracellular cAMP levels, resulting in bronchodilation and anti-inflammatory effects. Guaifenesin is an expectorant that increases respiratory tract fluid secretions to reduce mucus viscosity.
| Metabolism | Theophylline is primarily metabolized by cytochrome P450 enzymes, mainly CYP1A2, with minor contributions from CYP2E1 and CYP3A4. Guaifenesin is metabolized via oxidation and glucuronidation. |
| Excretion | Primarily renal (70-80% as unchanged drug), biliary/fecal (~15-20% as metabolites and unchanged drug) |
| Half-life | 4-6 hours in adults; prolonged to 8-12 hours in hepatic impairment or elderly patients |
| Protein binding | 50-60% bound to albumin and alpha-1-acid glycoprotein |
| Volume of Distribution | 0.3-0.5 L/kg; indicates distribution primarily into extracellular fluid |
| Bioavailability | Oral: 40-60%; rectal: 50-70%; inhalation: 10-30% |
| Onset of Action | Oral: 30-60 minutes; rectal: 20-40 minutes; inhalation: 5-15 minutes |
| Duration of Action | 4-8 hours for bronchodilation; sustained-release formulations provide up to 12 hours |
| Molecular Weight | 230.26 |
1-2 tablets (130-260 mg theophylline equivalent) orally every 6-8 hours; maximum 6 tablets/day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-59 mL/min: reduce dose by 25-50%; GFR <30 mL/min: reduce dose by 50% and monitor serum theophylline levels. |
| Liver impairment | Child-Pugh Class A: reduce dose by 50%; Child-Pugh Class B or C: reduce dose by 75% and monitor serum theophylline levels. |
| Pediatric use | Weight-based: 10-16 mg/kg/day theophylline equivalent divided every 6-8 hours; maximum 400 mg/day. Adjust based on serum levels. |
| Geriatric use | Elderly patients: initial dose of 130 mg orally every 8 hours; titrate gradually; monitor serum theophylline levels due to reduced clearance. |
| 1st trimester | Limited human data; animal studies show risk; potential for fetal harm. Use only if benefit outweighs risk. |
| 2nd trimester | Use only if clearly needed; consider maternal benefit vs fetal risk. |
| 3rd trimester | May cause premature closure of ductus arteriosus and fetal renal impairment; avoid in third trimester if possible. |
Clinical note
Comprehensive clinical and safety monograph for ASBRON (ASBRON).
| Placental transfer | Crosses placenta; observed in fetal serum at concentrations similar to maternal. |
| Breastfeeding | Excreted into breast milk in low amounts; manufacturers advise caution due to potential adverse effects in infants. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Asbron contains theophylline and guaifenesin. Theophylline: In first trimester, limited data suggest no major teratogenic risk (FDA category C). In second and third trimesters, no known teratogenicity but may cause fetal tachycardia, jitteriness, or transient neonatal effects (e.g., irritability, vomiting) due to transplacental passage. Guaifenesin: Limited human data; animal studies not indicative of teratogenicity. Overall, Asbron is considered relatively low risk, but non-pharmacologic measures preferred in first trimester. |
| Fetal Monitoring | Maternal: Serum theophylline levels (trough) to maintain therapeutic range (10-20 mcg/mL) as pregnancy reduces clearance; monitor for nausea, vomiting, tachycardia, insomnia, arrhythmias. Fetal: Heart rate monitoring if maternal toxicity signs; third trimester ultrasound to assess growth given possible vasoconstrictive effects. Neonatal: Evaluate for transient irritability, tachycardia, or feeding difficulties after birth. |
| Fertility Effects | No evidence of significant impact on fertility in either sex based on available data. Theophylline and guaifenesin have no known direct effects on gametogenesis or hormonal cycles. High doses of theophylline may rarely cause amenorrhea due to systemic effects, but this is not standard. |
■ FDA Black Box Warning
Theophylline has a narrow therapeutic index; serious adverse effects including seizures and arrhythmias can occur at levels close to therapeutic range. Do not exceed recommended doses. Use caution in patients with cardiac or hepatic impairment.
| Serious Effects |
Hypersensitivity to active substance or excipientsHistory of bronchospasm or anaphylactic reaction to NSAIDsActive peptic ulcer disease
| Precautions | Theophylline toxicity is dose-related; monitor serum levels. Caution in patients with peptic ulcer, hyperthyroidism, seizure disorders, or cardiovascular disease. Drug interactions with quinolones, macrolides, and cimetidine can increase theophylline levels. |
| Food/Dietary | Avoid high-fat meals with extended-release formulations as they may alter absorption. Limit caffeine-containing foods/beverages (coffee, tea, chocolate) due to additive CNS stimulation. No significant food interactions with guaifenesin. |
| Clinical Pearls | Asbron is a combination product containing theophylline and guaifenesin. Theophylline has a narrow therapeutic index; monitor serum levels (target 10-20 mcg/mL) due to variable metabolism. Guaifenesin is an expectorant but evidence for efficacy is limited. Avoid in patients with active peptic ulcer disease or seizure disorders. Cimetidine, fluoroquinolones, and macrolides increase theophylline levels; smoking and rifampin decrease levels. |
| Patient Advice | Take Asbron exactly as prescribed; do not crush or chew extended-release tablets. · Avoid excessive caffeine intake (coffee, tea, cola) as it may increase side effects. · Report symptoms of theophylline toxicity: nausea, vomiting, insomnia, tremors, fast heartbeat. · Do not stop abruptly; dosage tapering may be needed. · Stay hydrated to help guaifenesin work effectively. · Avoid alcohol as it may increase side effects like dizziness. |
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