1. Clinical Overview
A fixed-dose combination analgesic and antispasmodic agent. Dicyclomine is an anticholinergic/antispasmodic that relieves smooth muscle spasms in the gastrointestinal tract. Dextropropoxyphene is a centrally-acting opioid analgesic (narcotic) used for mild to moderate pain. Paracetamol (Acetaminophen) is a centrally-acting analgesic and antipyretic. This combination is primarily used for the symptomatic relief of moderate to severe pain associated with smooth muscle spasm, such as in renal or biliary colic, dysmenorrhea, and post-operative pain. The combination is highly controversial and has been banned or restricted in many countries due to the risk profile of dextropropoxyphene, including fatal cardiac arrhythmias and its narrow therapeutic index.
| Onset | Duration | Bioavailability |
|---|---|---|
| Dicyclomine: 1-2 hours (oral). Dextropropoxyphene: 30-60 minutes. Paracetamol: 30-60 minutes. | Dicyclomine: 4-6 hours. Dextropropoxyphene: 4-6 hours. Paracetamol: 4-6 hours. | Dicyclomine: ~67% (oral). Dextropropoxyphene: ~30-70% (oral, high first-pass metabolism). Paracetamol: ~88% (oral). |
2. Mechanism of Action
The combination provides analgesia through two distinct central mechanisms (opioid and paracetamol) and relieves visceral smooth muscle spasm peripherally via anticholinergic action. Dicyclomine acts as a competitive antagonist at muscarinic (M1, M3) receptors in the gastrointestinal tract, inhibiting acetylcholine-induced smooth muscle contraction. Dextropropoxyphene is a weak mu-opioid receptor agonist in the central nervous system, altering the perception of and emotional response to pain. Paracetamol's exact mechanism is not fully elucidated but is believed to involve central inhibition of prostaglandin synthesis (COX-2 and COX-3 inhibition) and modulation of serotonergic and cannabinoid pathways.
3. Indications & Uses
- Moderate to severe pain associated with smooth muscle spasm
- Renal colic (pain due to kidney stones)
- Biliary colic (pain due to gallstones)
- Severe dysmenorrhea (menstrual cramps)
4. Dosage & Administration
Adult Dosage: One tablet (Dicyclomine 20mg + Dextropropoxyphene 500mg + Paracetamol 325/500mg) every 6-8 hours as needed for pain. Maximum: 3 tablets in 24 hours. Should be used at the lowest effective dose for the shortest duration possible.
Administration: Take with or after food to minimize gastrointestinal upset. Swallow whole with a full glass of water. Do not crush, chew, or break the tablet. Do not consume alcohol. Use only for acute, short-term pain management (typically 3-5 days).
5. Side Effects
Common side effects may include:
- Drowsiness, sedation, dizziness
- Dry mouth
- Constipation
- Nausea, vomiting
- Blurred vision
- Sweating
- Headache
- Lightheadedness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Alcohol, Benzodiazepines (e.g., Alprazolam), Barbiturates | Profound additive CNS and respiratory depression. Increased risk of fatal overdose. | Major |
| Other Opioids (e.g., Codeine, Tramadol), CNS Depressants | Additive sedation, respiratory depression, and risk of toxicity. | Major |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Clarithromycin, Ritonavir) | Increased dextropropoxyphene levels, leading to toxicity (CNS, cardiac). | Major |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin) | Decreased dextropropoxyphene efficacy. | Moderate |
| Anticholinergics (e.g., Atropine, Tricyclic Antidepressants, Antihistamines) | Additive anticholinergic side effects (dry mouth, constipation, urinary retention, confusion). | Major |
| Warfarin | Paracetamol may potentiate anticoagulant effect with high-dose/prolonged use; monitor INR. | Moderate |
| MAO Inhibitors (e.g., Phenelzine, Selegiline) | Risk of serotonin syndrome, hyperpyrexia, excitation. Contraindicated. | Major |
| SSRIs/SNRIs (e.g., Fluoxetine, Venlafaxine) | Increased risk of serotonin syndrome. | Moderate |
| Antiarrhythmics (e.g., Amiodarone, Sotalol), Antipsychotics (e.g., Haloperidol) | Additive risk of QT prolongation and fatal arrhythmias. | Major |
7. Patient Counselling
- DO take exactly as prescribed by the doctor. Do not increase dose or frequency.
- DO take with food if stomach upset occurs.
- DO inform all your doctors and dentists that you are taking this medicine.
- DO keep the medicine in a safe place, out of reach of children and others.
- DONT consume alcohol in any form while on this medication.
- DONT drive, operate machinery, or perform hazardous tasks.
- DONT share your medicine with anyone else.
- DONT stop suddenly after long-term use; consult doctor for tapering.
8. Toxicology & Storage
Overdose: TRIPLE OVERDOSE MANIFESTATION: 1) Opioid (Dextropropoxyphene): Pinpoint pupils, respiratory depression (can be rapid and severe), cyanosis, stupor, coma, circulatory collapse, pulmonary edema, convulsions. 2) Anticholinergic (Dicyclomine): Hyperthermia, flushed/hot/dry skin, dilated pupils, tachycardia, urinary retention, ileus, delirium, hallucinations. 3) Paracetamol: Early (0-24h): Nausea, vomiting, anorexia, malaise. Late (24-72h): RUQ pain, elevated LFTs, jaundice, coagulopathy, hepatic encephalopathy, acute liver failure. Cardiac toxicity (QT prolongation, ventricular arrhythmias) can be prominent and fatal.
Storage: Store below 30°C, in a cool, dry place, protected from light and moisture. Keep in the original container, tightly closed. Keep out of reach and sight of children and pets. Do not use after the expiry date printed on the pack. Dispose of unused tablets safely (return to pharmacy) to prevent misuse.