1. Clinical Overview
Drotaverine is a potent, selective, and direct-acting antispasmodic agent belonging to the isoquinoline class. It is a papaverine derivative but lacks opioid receptor activity. It is widely used in the Indian clinical setting for the treatment of smooth muscle spasm associated with various gastrointestinal, genitourinary, and obstetric/gynecological conditions. Its primary mechanism is the selective inhibition of phosphodiesterase-IV (PDE-IV), leading to increased intracellular cyclic adenosine monophosphate (cAMP) and subsequent smooth muscle relaxation without significant anticholinergic or cardiovascular side effects.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: 30-45 minutes. Intramuscular: 10-15 minutes. | Approximately 4-6 hours after oral administration. | Approximately 60-70% after oral administration. |
2. Mechanism of Action
Drotaverine exerts its antispasmodic effect through selective and potent inhibition of the enzyme phosphodiesterase type IV (PDE-IV). This inhibition prevents the breakdown of intracellular cyclic adenosine monophosphate (cAMP). The increased cAMP levels activate protein kinase A (PKA), which phosphorylates specific proteins, leading to a decrease in intracellular calcium ion (Ca2+) concentration. Lowered Ca2+ levels inhibit the activity of myosin light-chain kinase (MLCK), resulting in smooth muscle relaxation.
3. Indications & Uses
- Smooth muscle spasm associated with Irritable Bowel Syndrome (IBS)
- Renal colic (ureteric spasm)
- Biliary colic (spasm of Oddi's sphincter)
- Dysmenorrhea (primary spasmodic dysmenorrhea)
- Spasm during endoscopic procedures (e.g., ERCP)
4. Dosage & Administration
Adult Dosage: 40-80 mg (4 to 8 tablets of 10mg) 2-3 times daily. Usual dose is 40 mg (1 tablet of 40mg or 4 tablets of 10mg) three times a day.
Administration: Tablets should be swallowed whole with a glass of water, with or without food. Do not crush or chew. For acute colic, a loading dose may be administered as per physician's advice.
5. Side Effects
Common side effects may include:
- Headache
- Dizziness/lightheadedness
- Nausea
- Constipation or diarrhea
- Dry mouth (rare with this agent)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Levodopa | Drotaverine may reduce the bioavailability and efficacy of levodopa. | Moderate |
| Other Hypotensive Agents (e.g., ACE inhibitors, beta-blockers, nitrates) | Additive hypotensive effect; risk of dizziness and fainting. | Moderate |
| CYP450 Inhibitors (e.g., Cimetidine, Ketoconazole, Erythromycin) | May increase drotaverine plasma levels, increasing risk of side effects. | Moderate |
| CYP450 Inducers (e.g., Rifampicin, Phenobarbital, Carbamazepine) | May decrease drotaverine plasma levels, reducing efficacy. | Moderate |
| Papaverine | Additive pharmacological effect; increased risk of adverse reactions. | Moderate |
7. Patient Counselling
- Do take the tablet as prescribed, do not double the dose.
- Do inform your doctor about all other medicines you are taking.
- Don't consume alcohol while on this medication.
- Don't drive or operate heavy machinery if you feel dizzy.
- Do store the medicine in a cool, dry place away from children.
8. Toxicology & Storage
Overdose: Symptoms are extensions of pharmacological effects: severe hypotension, cardiac arrhythmias (tachycardia, ventricular extrasystoles), dizziness, nausea, vomiting, confusion, and potentially respiratory depression.
Storage: Store below 30°C. Protect from light and moisture. Keep the container tightly closed. Keep out of reach of children. Do not use after the expiry date printed on the pack.