PHRENILIN WITH CAFFEINE AND CODEINE
Clinical safety rating: avoid
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur especially in CYP2D6 ultra-rapid metabolizers.
Combination analgesic; butalbital is a barbiturate that potentiates GABA-A activity; acetaminophen inhibits cyclooxygenase (COX) and modulates cannabinoid receptors; caffeine is a nonselective adenosine receptor antagonist; codeine is a prodrug converted to morphine, a mu-opioid agonist.
| Metabolism | Butalbital: hepatic (CYP2C19); Acetaminophen: hepatic (CYP1A2, CYP2E1, conjugation); Caffeine: hepatic (CYP1A2); Codeine: hepatic via CYP2D6 to morphine; also metabolized by CYP3A4 to norcodeine. |
| Excretion | Renal: butalbital ~60% unchanged; codeine ~90% as metabolites (free and conjugated morphine, norcodeine); caffeine <2% unchanged, ~80% as metabolites (paraxanthine, theobromine, theophylline) via renal excretion. Biliary/fecal: minimal. |
| Half-life | Butalbital: 35–50 hours; codeine: 2.5–3.5 hours; caffeine: 4–6 hours (adults), prolonged in liver disease. Clinical context: butalbital's long half-life leads to accumulation with repeated dosing; codeine's short half-life requires frequent dosing. |
| Protein binding | Butalbital: ~45% (albumin); codeine: ~7–25% (albumin); caffeine: ~10–30% (albumin). |
| Volume of Distribution | Butalbital: 0.8 L/kg; codeine: 3–4 L/kg; caffeine: 0.5–0.7 L/kg. Clinical meaning: codeine's high Vd indicates extensive tissue distribution; butalbital and caffeine are more confined to extracellular water. |
| Bioavailability | Oral: butalbital ~90%; codeine ~90% (but extensive first-pass metabolism to morphine); caffeine ~100%. |
| Onset of Action | Oral: butalbital 30–60 min; codeine 30–60 min; caffeine 45–60 min. |
| Duration of Action | Butalbital: 4–6 hours (analgesia, sedation); codeine: 4–6 hours; caffeine: 4–6 hours. Clinical note: sedation from butalbital may persist longer than analgesia. |
| Molecular Weight | Codeine: 299.36 Da; Butalbital: 224.26 Da; Caffeine: 194.19 Da |
1-2 capsules orally every 4 hours as needed, not to exceed 8 capsules per day. Each capsule contains butalbital 50 mg, caffeine 40 mg, and codeine phosphate 30 mg.
| Dosage form | CAPSULE |
| Renal impairment | No specific guidelines available. Use with caution in renal impairment; consider reducing dose or extending interval. Monitor for CNS depression and constipation. For GFR < 30 mL/min, use is not recommended. |
| Liver impairment | Contraindicated in patients with severe hepatic impairment (Child-Pugh class C). In mild to moderate hepatic impairment (Child-Pugh A or B), use with caution; consider reducing dose or extending interval. Monitor for excessive sedation. |
| Pediatric use | Not recommended for use in children under 12 years of age. For children 12-18 years, weight-based dosing for codeine: 0.5-1 mg/kg codeine component every 4-6 hours as needed; maximum codeine dose 60 mg/dose. Butalbital and caffeine dosing not established in pediatrics; alternative therapy recommended. |
| Geriatric use | Start at the lower end of the dosing range (e.g., 1 capsule every 6 hours as needed). Monitor for increased sensitivity to CNS depressant effects, falls, confusion, and constipation. Consider reducing total daily dose. Avoid in frail elderly. |
| 1st trimester | Avoid; limited data but potential teratogenic risk from codeine and butalbital. Use only if benefit outweighs risk. |
| 2nd trimester | Caution; butalbital and codeine may cause fetal dependence and withdrawal. Use only if clearly needed. |
| 3rd trimester | Avoid; prolonged use may lead to neonatal withdrawal symptoms due to opioid and barbiturate exposure. Risk of respiratory depression in neonate if used near term. |
Clinical note
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur especially in CYP2D6 ultra-rapid metabolizers.
| FDA category | Positive |
| Placental transfer | Codeine, butalbital, and caffeine cross the placenta. Codeine and its active metabolite morphine are extensively transferred. Butalbital readily crosses the placental barrier. Caffeine also crosses. |
■ FDA Black Box Warning
Codeine is contraindicated in children younger than 12 years for pain relief, and contraindicated in children younger than 18 years for tonsillectomy/adenoidectomy due to risk of fatal respiratory depression.
| Common Effects | cough |
| Serious Effects |
Hypersensitivity to any componentAcute or severe bronchial asthma or respiratory depressionKnown CYP2D6 ultra-rapid metabolizerConcurrent use of MAO inhibitors or within 14 daysPorphyria (butalbital can precipitate attacks)Obstructive sleep apnea
| Precautions | Risk of respiratory depression; addiction and abuse potential; acetaminophen hepatotoxicity (dose-dependent); avoid in patients with severe hepatic impairment; CYP2D6 ultra-rapid metabolizers may experience toxicity with codeine; butalbital can cause dependence and withdrawal; avoid abrupt discontinuation; may impair mental/physical abilities. |
| Food/Dietary |
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| Breastfeeding | Codeine and butalbital are excreted into breast milk in low amounts. In mothers with CYP2D6 ultra-rapid metabolizer phenotype, codeine can produce high morphine levels, posing risk to infant. Butalbital may cause infant sedation. Generally, avoid during breastfeeding; if necessary, use lowest effective dose and monitor infant for drowsiness, respiratory depression, and feeding difficulties. |
| Lactation Rating | L4 (Possibly Hazardous) |
| Teratogenic Risk | First trimester: Codeine (FDA Category C) and butalbital (Category C/D near term) may be associated with increased risk of congenital malformations; caffeine (Category C) at high doses may increase risk of miscarriage. Second and third trimesters: Chronic use may lead to fetal dependence, neonatal withdrawal syndrome; butalbital near term may cause neonatal bleeding due to vitamin K deficiency; codeine may cause respiratory depression if used near delivery. |
| Fetal Monitoring | Monitor maternal blood pressure, respiratory rate, and pain scores. Assess for signs of sedation or respiratory depression. For fetus: ultrasonography for growth restriction if used chronically. At delivery, monitor neonatal respiratory status, Apgar scores, and signs of withdrawal (e.g., irritability, tremors, feeding problems). |
| Fertility Effects | Data limited. Codeine and butalbital may affect ovulation via CNS depressant effects; caffeine at high doses may impair fertility. No definitive evidence of long-term infertility. Discontinuation during pregnancy planning should be based on clinical need. |
| Avoid grapefruit juice (may increase butalbital levels); limit or avoid caffeine-containing foods/beverages (coffee, tea, chocolate, cola) to prevent additive stimulation. |
| Clinical Pearls | Monitor respiratory depression risk, especially in elderly or COPD patients; avoid concurrent use with other CNS depressants; assess liver function due to butalbital metabolism; caffeine may exacerbate anxiety or insomnia. |
| Patient Advice | Do not exceed prescribed dose; may cause drowsiness, avoid driving or operating machinery. · Avoid alcohol and other sedatives; risk of severe drowsiness or breathing problems. · Store securely; risk of abuse and dependence; do not share with others. · Report symptoms of withdrawal (e.g., anxiety, insomnia) when discontinuing. · Caffeine content may cause jitteriness, palpitations, or sleep disturbances. |