1. Clinical Overview
Drotaverine is a synthetic, non-anticholinergic, papaverine-like antispasmodic agent. It is a selective inhibitor of phosphodiesterase type 4 (PDE4) and a calcium channel modulator, leading to smooth muscle relaxation. It is widely used in India for the treatment of smooth muscle spasm associated with gastrointestinal, biliary, genitourinary, and gynecological conditions. It is particularly valued for its efficacy in renal and biliary colic, dysmenorrhea, and irritable bowel syndrome, with a favorable safety profile and minimal anticholinergic side effects.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: 30-45 minutes. Intramuscular: 10-15 minutes. | Approximately 4-6 hours. | Approximately 60-70% after oral administration. |
2. Mechanism of Action
Drotaverine exerts its antispasmodic effect through two primary, synergistic mechanisms: 1) Selective and potent inhibition of the enzyme phosphodiesterase type 4 (PDE4), leading to an intracellular accumulation of cyclic adenosine monophosphate (cAMP). Increased cAMP activates protein kinase A (PKA), which phosphorylates and inactivates myosin light-chain kinase (MLCK), resulting in smooth muscle relaxation. 2) Modulation of calcium ion (Ca2+) influx, possibly via inhibition of voltage-gated L-type calcium channels, reducing intracellular calcium concentration required for muscle contraction.
3. Indications & Uses
- Smooth muscle spasm in renal colic (ureteric colic)
- Smooth muscle spasm in biliary colic (gallbladder/bile duct spasm)
- Primary dysmenorrhea (menstrual cramps)
- Irritable Bowel Syndrome (IBS) with abdominal cramping and pain
4. Dosage & Administration
Adult Dosage: 40-80 mg orally, 2 to 3 times daily. Maximum daily dose: 240 mg. For acute colic: 80 mg initially, may repeat after 4-6 hours if needed.
Administration: Tablet should be swallowed whole with a glass of water, with or without food. Can be taken on an empty stomach for faster relief in acute pain. Do not crush or chew.
5. Side Effects
Common side effects may include:
- Nausea
- Headache
- Dizziness
- Constipation
- Dry mouth (rare compared to anticholinergics)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Levodopa | Potentiates hypotensive and bradycardic effects of Levodopa; risk of severe cardiovascular depression. | High |
| Other Antihypertensives (e.g., Beta-blockers, ACE inhibitors) | Additive hypotensive effect. | Moderate |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Clarithromycin, Ritonavir) | May increase drotaverine plasma levels, increasing risk of side effects. | Moderate |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin) | May decrease drotaverine plasma levels, reducing efficacy. | Moderate |
| Sedatives/Hypnotics (e.g., Alprazolam, Zolpidem) | Potential additive sedative effect with dizziness. | Low |
7. Patient Counselling
- Do take the tablet as prescribed, do not exceed the recommended dose.
- Do inform your doctor about all other medicines you are taking.
- Don't take it if you are allergic to drotaverine.
- Don't crush or chew the tablet.
- Don't use it for pain that is not colicky or spastic in nature.
8. Toxicology & Storage
Overdose: Symptoms may include severe hypotension, cardiac arrhythmias (bradycardia, tachycardia), dizziness, nausea, vomiting, sedation, and respiratory depression.
Storage: Store below 30°C in a cool, dry place, protected from light and moisture. Keep out of reach of children.