RESPORAL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for RESPORAL (RESPORAL).
RESPORAL contains theophylline, a methylxanthine that inhibits phosphodiesterase (PDE) isoenzymes, leading to increased intracellular cAMP and cGMP levels. It also antagonizes adenosine receptors, resulting in bronchodilation and anti-inflammatory effects.
| Metabolism | Primarily hepatic via cytochrome P450 enzymes, including CYP1A2, CYP2E1, and CYP3A4. Approximately 90% of theophylline is metabolized in the liver. |
| Excretion | Renal excretion accounts for 70% of elimination (30% unchanged), biliary/fecal 20%, and 10% metabolized. |
| Half-life | Terminal half-life is 12 hours (range 10-14 h), supporting twice-daily dosing in most patients. |
| Protein binding | 95% bound to albumin. |
| Volume of Distribution | Vd 0.5 L/kg, indicating moderate tissue distribution. |
| Bioavailability | Oral: 80%; inhaled: 25% (due to local deposition and first-pass metabolism). |
| Onset of Action | Oral: 30-60 minutes; IV: immediate; inhaled: 5-15 minutes. |
| Duration of Action | Oral: 12 hours; IV: 6-8 hours; inhaled: 4-6 hours. |
2 mg orally twice daily
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | GFR 30-59 mL/min: 1 mg orally twice daily; GFR <30 mL/min: 1 mg orally once daily |
| Liver impairment | Child-Pugh Class A: 2 mg orally twice daily; Class B: 1 mg orally twice daily; Class C: not recommended |
| Pediatric use | Weight <30 kg: 1 mg orally twice daily; Weight ≥30 kg: 2 mg orally twice daily |
| Geriatric use | Age ≥65 years: 1 mg orally twice daily; monitor for renal function and adjust dose accordingly |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for RESPORAL (RESPORAL).
| Breastfeeding | Excreted in breast milk; M/P ratio unknown. Use with caution due to potential for infant respiratory depression and GI effects. Consider benefits of breastfeeding vs. risk. |
| Teratogenic Risk | First trimester: Limited data; animal studies show no teratogenicity at clinically relevant doses. Second/third trimesters: Associated with decreased uterine blood flow; avoid use unless benefit outweighs risk. Peripartum: May cause transient respiratory depression in neonates if used near term. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to theophylline or any component of the formulation.","Pre-existing arrhythmias (e.g., tachyarrhythmias, atrial fibrillation, ventricular arrhythmias) unless controlled.","Active seizure disorder unless on appropriate anticonvulsant therapy.","Uncontrolled peptic ulcer disease."]
| Precautions | ["Cardiovascular toxicity: arrhythmias, hypotension, tachycardia; risk increases with serum levels >20 mcg/mL.","Seizures: may occur at toxic concentrations, especially in patients with pre-existing seizure disorders or conditions that lower seizure threshold.","Gastrointestinal effects: nausea, vomiting, and diarrhea; may be signs of toxicity.","Drug interactions: caution with drugs that inhibit (e.g., cimetidine, ciprofloxacin, fluvoxamine) or induce (e.g., rifampin, phenobarbital, carbamazepine) CYP1A2.","Metabolic effects: hypokalemia, hyperglycemia, and metabolic acidosis in overdose.","Hepatic impairment: reduce dose in patients with hepatic insufficiency.","Pregnancy: use only if clearly needed; crosses placenta."] |
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| Monitor fetal heart rate and uterine activity during prolonged use. Assess neonatal respiratory status post-delivery if used near term. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment. |