1. Clinical Overview
A topical combination formulation containing a local anesthetic (Lidocaine) and a calcium channel blocker (Nifedipine). It is primarily indicated for the treatment of chronic anal fissures and hemorrhoids, providing symptomatic relief from pain and spasm while promoting healing. The combination targets both neuropathic pain (via sodium channel blockade) and smooth muscle spasm of the internal anal sphincter (via calcium channel blockade).
| Onset | Duration | Bioavailability |
|---|---|---|
| Lidocaine: 2-5 minutes for topical anesthesia. Nifedipine: Reduction in anal sphincter pressure may begin within 30 minutes, with significant effect in 1-2 hours. | Lidocaine: 30 minutes to 2 hours (topical). Nifedipine: Effect on sphincter tone can last 4-6 hours post-application. | Topical absorption is low and variable. Systemic absorption of Lidocaine from intact skin is <3%. Nifedipine absorption via perianal mucosa is estimated to be <5-10%. |
2. Mechanism of Action
The combination works synergistically. Lidocaine blocks voltage-gated sodium channels in neuronal membranes, inhibiting the initiation and conduction of nerve impulses, thereby providing local anesthesia and pain relief. Nifedipine blocks L-type calcium channels in vascular and gastrointestinal smooth muscle cells, leading to a reduction in intracellular calcium. In the internal anal sphincter, this causes chemical sphincterotomy - reducing resting anal pressure and spasm, improving blood flow to the anal mucosa, and promoting healing of fissures.
3. Indications & Uses
- Chronic Anal Fissure (non-healing > 6 weeks)
- Acute Anal Fissure with severe pain and spasm
- Hemorrhoids (especially thrombosed or painful) for symptomatic relief
4. Dosage & Administration
Adult Dosage: Apply a pea-sized amount (approximately 0.5 to 1 gram) topically to the affected perianal area, 2-3 times daily, especially after bowel movements and at bedtime. Duration: Typically 6-8 weeks for chronic fissures.
Administration: 1. Wash hands before and after application. 2. Clean and dry the perianal area gently. 3. Apply a thin layer externally to the anal verge and, if possible, gently apply a small amount just inside the anal canal using a finger cot or applicator. 4. Avoid deep insertion. 5. Do not use with occlusive dressings.
5. Side Effects
Common side effects may include:
- Local burning or stinging sensation (usually transient)
- Itching (pruritus) at application site
- Skin dryness or erythema
- Headache (less frequent than with nitrates)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Beta-blockers (e.g., Propranolol, Atenolol) | Increased risk of hypotension, bradycardia, and heart failure. Potentiates negative inotropic effects. | Major |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Itraconazole, Erythromycin, Clarithromycin, Ritonavir) | Markedly increased systemic levels of Nifedipine, leading to severe hypotension and edema. | Major |
| Other Antiarrhythmics (e.g., Amiodarone) | Increased risk of cardiac arrhythmias with systemic Lidocaine. | Major |
| Other Local Anesthetics | Additive toxic effects if used concurrently on other body sites. | Moderate |
| Antihypertensives (Diuretics, ACE Inhibitors) | Additive hypotensive effect. | Moderate |
| CYP1A2 Inducers (e.g., Smoking) | May reduce Lidocaine efficacy. | Minor |
7. Patient Counselling
- DO wash hands before and after application.
- DO clean the area gently with water and pat dry before applying.
- DO use only a pea-sized amount.
- DON'T insert the tube or applicator deep into the rectum.
- DON'T apply to broken skin or open wounds unless directed by a doctor.
- DON'T use occlusive dressings (like plastic wraps) over the area.
- DON'T increase the dose or frequency without medical advice.
8. Toxicology & Storage
Overdose: Topical overdose (excessive amount/frequency): Systemic Lidocaine toxicity: Tinnitus, metallic taste, perioral numbness, dizziness, tremors, seizures, respiratory depression, cardiovascular collapse. Systemic Nifedipine toxicity: Severe hypotension, reflex tachycardia, palpitations, flushing, peripheral edema, syncope.
Storage: Store at room temperature (15-25°C), protected from light and moisture. Do not freeze. Keep the tube tightly closed. Keep out of reach of children. Do not use after the expiry date printed on the tube/carton.