SYNALGOS-DC-A
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SYNALGOS-DC-A (SYNALGOS-DC-A).
SYNALGOS-DC-A contains dihydrocodeine, which is a semisynthetic opioid agonist; aspirin, a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX) enzymes; and caffeine, a central nervous system stimulant. Dihydrocodeine binds to mu-opioid receptors in the central nervous system to produce analgesia. Aspirin irreversibly acetylates COX-1 and COX-2, reducing prostaglandin synthesis. Caffeine enhances analgesia via adenosine receptor antagonism and possibly by increasing drug absorption.
| Metabolism | Dihydrocodeine is metabolized primarily via CYP2D6 to dihydromorphine (active) and through CYP3A4 to nordihydrocodeine (inactive). Aspirin is rapidly hydrolyzed to salicylate, which is further metabolized by conjugation and oxidation pathways, primarily hepatic. Caffeine is metabolized by CYP1A2 to paraxanthine and other metabolites. |
| Excretion | Renal: ~70-80% as free and conjugated propoxyphene; norpropoxyphene is renally eliminated; biliary: 10-20%; fecal: <10% |
| Half-life | Propoxyphene: 6-12 hours; norpropoxyphene: 30-36 hours; clinical context: prolonged with hepatic impairment, age >60 years, and renal dysfunction; accumulation of norpropoxyphene may cause cardiotoxicity |
| Protein binding | Propoxyphene: ~78% bound primarily to albumin; norpropoxyphene: ~60-70% bound |
| Volume of Distribution | Propoxyphene: 12-20 L/kg; indicates extensive tissue distribution |
| Bioavailability | Oral: ~30-60% due to extensive first-pass metabolism; rectal: not applicable; other routes: not applicable |
| Onset of Action | Oral: 30-60 minutes |
| Duration of Action | Oral: 4-6 hours; analgesic effect may persist longer due to active metabolite |
1-2 capsules orally every 4-6 hours as needed for pain; each capsule contains dihydrocodeine bitartrate 16 mg, acetaminophen 356.4 mg, and caffeine 30 mg.
| Dosage form | CAPSULE |
| Renal impairment | eGFR 30-59 mL/min: administer every 6 hours; eGFR 15-29 mL/min: administer every 8-12 hours; eGFR <15 mL/min: not recommended due to accumulation of dihydrocodeine and acetaminophen. |
| Liver impairment | Child-Pugh A: reduce dose by 50% or extend interval to every 6-8 hours; Child-Pugh B: use with caution, reduce dose by 75% or extend interval to every 8-12 hours; Child-Pugh C: contraindicated. |
| Pediatric use | Not recommended for children under 12 years; for children 12-18 years, dose based on weight: 0.5-1 mg/kg dihydrocodeine equivalent (max 60 mg dihydrocodeine per dose) every 4-6 hours as needed; avoid exceeding 4 doses in 24 hours. |
| Geriatric use | Initiate at lowest dose (1 capsule every 6 hours) and titrate slowly; monitor for respiratory depression and constipation; reduce dose by 25-50% in patients >65 years with renal or hepatic impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SYNALGOS-DC-A (SYNALGOS-DC-A).
| Breastfeeding | Codeine: M/P ratio ~2.6; potential for infant toxicity (CNS depression, apnea) especially in CYP2D6 ultrarapid metabolizers. Aspirin: M/P ratio ~0.03-0.09; risk of Reye syndrome and platelet dysfunction in infant. Discontinue breastfeeding or avoid drug; short-term use with infant monitoring if unavoidable. |
| Teratogenic Risk | First trimester: No adequate studies; potential for neural tube defects due to aspirin component at high doses. Second/third trimester: Aspirin increases risk of premature closure of ductus arteriosus, low birth weight, and peripartum hemorrhage; codeine may cause neonatal respiratory depression, withdrawal syndrome, and risk of persistent pulmonary hypertension. Avoid in third trimester unless essential. |
■ FDA Black Box Warning
Addiction, Abuse, and Misuse: SYNALGOS-DC-A exposes users to risks of opioid addiction, abuse, and misuse, which can lead to overdose and death. Assess each patient's risk before prescribing; monitor regularly. Life-Threatening Respiratory Depression: Serious, life-threatening, or fatal respiratory depression may occur. Monitor for respiratory depression, especially during initiation or after dose increase. Neonatal Opioid Withdrawal Syndrome: Prolonged use during pregnancy can result in neonatal opioid withdrawal syndrome, which may be life-threatening and requires management according to protocols developed by neonatology experts. Concomitant Use with Benzodiazepines or Other CNS Depressants: Concomitant use of opioids with benzodiazepines or other CNS depressants may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing for patients for whom alternative treatment options are inadequate; limit dosages and durations to the minimum required; follow patients for signs and symptoms of respiratory depression and sedation. Risks from Concomitant Use with CYP3A4 Inducers or Inhibitors: Concomitant use of SYNALGOS-DC-A with all CYP3A4 inducers or inhibitors may result in changes in dihydrocodeine exposure; follow patients for respiratory depression and sedation at frequent intervals.
| Serious Effects |
["Hypersensitivity to dihydrocodeine, aspirin, caffeine, or any component","Significant respiratory depression","Acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment","Known or suspected gastrointestinal obstruction, including paralytic ileus","Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of such therapy","Children with viral infections (due to aspirin component, risk of Reye's syndrome)","Hemophilia (due to aspirin component)","Peptic ulcer disease (active or history, due to aspirin component)"]
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| Fetal Monitoring | Monitor fetal growth and amniotic fluid index via ultrasound; fetal heart rate monitoring during third trimester for signs of ductus arteriosus constriction; monitor maternal bleeding time and platelet function if used near term; assess neonatal Apgar scores, respiratory status, and signs of opioid withdrawal postpartum. |
| Fertility Effects | Non-steroidal anti-inflammatory drugs (aspirin component) can inhibit ovulation by interfering with prostaglandin synthesis; codeine may impair male and female fertility via hormonal disruption. Reversible upon discontinuation. |
| Precautions | ["Addiction, Abuse, and Misuse","Life-Threatening Respiratory Depression","Neonatal Opioid Withdrawal Syndrome","Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants","Risks from Concomitant Use with CYP3A4 Inducers or Inhibitors","Adrenal Insufficiency","Severe Hypotension","Gastrointestinal Effects (risk of GI bleeding due to aspirin)","Reye's syndrome (aspirin use in children with viral infections)","Bleeding risk (aspirin)","Serotonin syndrome with concomitant serotonergic drugs","Anaphylaxis and hypersensitivity reactions"] |