SYNOPHYLATE
Clinical safety rating
cautionComprehensive clinical and safety monograph for SYNOPHYLATE (SYNOPHYLATE).
SYNOPHYLATE is a bronchodilator that inhibits phosphodiesterase, leading to increased intracellular cAMP. It also acts as an adenosine receptor antagonist and enhances histone deacetylase activity, causing relaxation of bronchial smooth muscle.
| Metabolism | Primarily hepatic via CYP1A2 and CYP3A4 isoenzymes. |
| Excretion | Renal excretion of unchanged drug accounts for approximately 10-20% of elimination; hepatic metabolism via CYP450 (primarily CYP1A2, CYP3A4) accounts for the remainder. Biliary/fecal excretion of metabolites is minor (<5%). |
| Half-life | Terminal elimination half-life is 3-4 hours in healthy adults, but can be prolonged to 6-8 hours in neonates, cirrhotic patients, or those with heart failure. Clinical context: Requires frequent dosing or extended-release formulations to maintain therapeutic levels. |
| Protein binding | Approximately 40-60% bound, primarily to albumin. |
| Volume of Distribution | Vd is approximately 0.3-0.7 L/kg, indicating distribution into total body water. Higher Vd in hyperthyroid states, lower in obesity. |
| Bioavailability | Oral: 80-100% for immediate-release; 90-100% for extended-release. Rectal: 80-90%. |
| Onset of Action | Oral immediate-release: 15-30 minutes. Intravenous: 1-5 minutes. Rectal: 20-30 minutes. |
| Duration of Action | Oral immediate-release: 4-6 hours. Extended-release: 8-12 hours. Intravenous: 2-4 hours after bolus. Clinical notes: Duration is dose-dependent and varies with metabolic rate. |
| Molecular Weight | 595.7 |
400-800 mg orally every 6-8 hours; maximum 3200 mg/day.
| Dosage form | ELIXIR |
| Renal impairment | GFR 30-50 mL/min: 50% of normal dose; GFR <30 mL/min: 25% of normal dose or extend interval to 12-24 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 50% of normal dose; Child-Pugh C: contraindicated or 25% of normal dose with monitoring. |
| Pediatric use | 10-15 mg/kg/dose orally every 6-8 hours; maximum 60 mg/kg/day. |
| Geriatric use | Start at 300 mg every 8 hours; titrate cautiously due to increased risk of accumulation and adverse effects. |
| 1st trimester | Avoid due to lack of safety data. May cause teratogenic effects (animal studies). |
| 2nd trimester | Use only if benefit > risk. Limited human data. May cause fetal tachycardia. |
| 3rd trimester | Use only if benefit > risk. May cause premature labor or fetal tachycardia. |
Clinical note
Comprehensive clinical and safety monograph for SYNOPHYLATE (SYNOPHYLATE).
| Placental transfer | Crosses placenta; degree proportional to maternal dose. Fetal plasma concentrations may reach 50% of maternal levels. |
| Breastfeeding | Excreted into breast milk in low concentrations. Monitor infant for signs of beta-2 agonist stimulation (tachycardia, irritability). Avoid or use with caution. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Increased risk of neural tube defects and cardiovascular malformations. Second and third trimesters: Risk of fetal growth restriction, oligohydramnios, and fetal nephrotoxicity. Late third trimester: Risk of premature closure of ductus arteriosus and persistent pulmonary hypertension of the newborn. |
| Fetal Monitoring | Maternal: Renal function, liver enzymes, blood pressure, and serum drug levels every 2 weeks. Fetal: Ultrasound for growth and amniotic fluid index monthly after viability, fetal echocardiography at 20-22 weeks due to cardiovascular risk. |
| Fertility Effects | Reversible impairment of spermatogenesis in males and ovulation inhibition in females due to interference with prostaglandin synthesis; effects resolve within 3 months of discontinuation. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to SYNOPHYLATE or any componentTachyarrhythmiasHypokalemiaPre-existing cardiac disease (e.g., hypertrophic obstructive cardiomyopathy)
| Precautions | Narrow therapeutic index; monitor serum levels. Dosage should be individualized. Avoid excessive caffeine intake. |
| Food/Dietary | Avoid excessive intake of caffeine (coffee, tea, cola, chocolate) and charcoal-grilled foods, which can reduce theophylline absorption. High-fat meals may increase absorption; take consistently with meals. |
| Clinical Pearls | SYNOPHYLATE (theophylline) has a narrow therapeutic index; serum levels should be monitored to maintain 5-15 mcg/mL. Use with caution in patients with heart failure, liver disease, or COPD, as clearance is reduced. Cimetidine, fluoroquinolones, and macrolides increase levels; smoking and carbamazepine decrease levels. Avoid in seizure disorders. |
| Patient Advice | Take exactly as prescribed; do not change dose without consulting your doctor. · Avoid caffeine-containing products (coffee, tea, cola, chocolate) as they may increase side effects. · Report symptoms of toxicity: persistent nausea, vomiting, insomnia, rapid heartbeat, or seizures. · Do not smoke or stop smoking without medical advice, as it affects drug levels. · Inform all healthcare providers you are taking this medication, especially if starting new drugs. |
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