VIGOREX® (Sildenafil): A Guide to Erectile Dysfunction Treatment

MEDICAL INFORMATION: This is a prescription medication. The following is for educational purposes only and is not a substitute for professional medical advice. Do not use this product without a doctor’s prescription and an appropriate cardiovascular evaluation.

Manufacturer

SIGMA Pharmaceutical Industries, Egypt.

Category & Active Ingredient

• Category: Phosphodiesterase type 5 (PDE5) inhibitor; treatment for erectile dysfunction (ED).
• Active Ingredient: Sildenafil (as sildenafil citrate).

Summary

VIGOREX® contains sildenafil, a PDE5 inhibitor used to treat erectile dysfunction by enhancing the natural erectile response to sexual stimulation. It increases blood flow to the penis by sustaining levels of cyclic guanosine monophosphate (cGMP) in penile tissue. It does not increase sexual desire and works only in the presence of sexual arousal.

Available Forms & Strengths

Available in oral, film-coated tablets:

• VIGOREX 50 mg film-coated tablets.
• VIGOREX 100 mg film-coated tablets.

Mechanism of Action

1. Sexual stimulation triggers nitric oxide (NO) release in the corpus cavernosum.
2. NO activates guanylate cyclase → increases cGMP → smooth muscle relaxation → increased blood inflow → erection.
3. PDE5 breaks down cGMP, ending the erection.
4. Sildenafil selectively inhibits PDE5, slowing cGMP breakdown and supporting erection in response to sexual stimulation.

Indications for VIGOREX®

• Treatment of erectile dysfunction (inability to achieve/maintain an erection sufficient for satisfactory sexual activity).
• Can be effective across common comorbidities (e.g., diabetes, hypertension) when prescribed after appropriate medical evaluation.

Dosage and Administration

• Standard starting dose: 50 mg taken about 1 hour before anticipated sexual activity (effective window ~30 minutes to 4 hours).
• Titration: Adjust based on response and tolerability to 25 mg or 100 mg. Do not exceed one dose per day.
• Food: A high-fat meal may delay onset and lower peak effect; for faster onset, take on an empty stomach.
• Special populations (initial dose 25 mg): adults ≥65 years, severe renal impairment, or hepatic impairment.

⚠ Critical Contraindications

• All nitrates & nitric oxide donors: e.g., nitroglycerin (any form), isosorbide dinitrate/mononitrate, “poppers” (amyl nitrite). Combination can cause severe, potentially fatal hypotension. Avoid nitrates for at least 24 hours after sildenafil.
• Guanylate cyclase stimulators: e.g., riociguat — contraindicated due to marked hypotension risk.
• Known hypersensitivity to sildenafil or any excipients.

Other Precautions

• Cardiovascular assessment required: Use with caution in patients with recent MI or stroke, unstable angina, severe hypotension/uncontrolled hypertension, heart failure, or life-threatening arrhythmias.
• Priapism risk: Seek immediate care for erections >4 hours. Use cautiously in conditions predisposing to priapism (e.g., sickle cell disease, multiple myeloma, leukemia) or anatomical penile deformation (e.g., Peyronie’s disease).
• Vision/hearing: Rare cases of NAION (sudden vision loss) and sudden hearing decrease/loss have been reported; discontinue and seek urgent care if these occur.
• Bleeding risk: Use cautiously with active peptic ulcer disease or bleeding disorders.

Side Effects

Generally mild to moderate and transient:

• Headache, facial flushing, dizziness.
• Dyspepsia (indigestion), nasal congestion.
• Visual effects (e.g., blue/green tinge, increased light sensitivity, blurred vision).
• Less common: back pain, myalgia, nausea, rash. Rare: priapism, severe hypotension, sudden vision/hearing loss (seek urgent care).

Pharmacokinetics

• Absorption: Oral bioavailability ~40%. T_max ~30–120 min (median ~60 min). High-fat meals delay T_max by ~1 hour and reduce C_max (~25–30%).
• Distribution: Apparent volume of distribution ~105 L; ~96% protein bound.
• Metabolism: Hepatic via CYP3A4 (major) and CYP2C9 (minor) to N-desmethyl metabolite (≈50% PDE5 potency); metabolite exposure ≈40% of parent (contributes ~20–25% of overall effect).
• Elimination: Terminal half-life ~3–5 hours. Excreted largely as metabolites: feces (~80%), urine (~13%).
• Special populations: Exposure increases in elderly, severe renal impairment, and hepatic impairment — consider 25 mg starting dose.

Drug Interactions

• Absolute contraindications:
  • Nitrates / NO donors (e.g., nitroglycerin, isosorbide dinitrate/mononitrate, amyl nitrite).
  • Riociguat (guanylate cyclase stimulator).
• CYP3A4 inhibitors ↑ sildenafil levels:
  • Strong: ritonavir, saquinavir, ketoconazole, itraconazole, clarithromycin, cobicistat. Use lowest dose (25 mg); with ritonavir, do not exceed 25 mg within 48 hours.
  • Moderate: erythromycin, diltiazem, verapamil, fluconazole, grapefruit juice — consider 25 mg and monitor for hypotension/AE.
• CYP3A4 inducers ↓ sildenafil levels: rifampin, carbamazepine, phenytoin, bosentan, St John’s wort — may reduce efficacy.
• Alpha-blockers (e.g., doxazosin, tamsulosin): Risk of symptomatic hypotension. Ensure patient is hemodynamically stable on alpha-blocker before starting sildenafil; initiate sildenafil at 25 mg and separate dosing if possible.
• Antihypertensives: Additive BP-lowering possible (generally modest). Monitor symptoms (dizziness, light-headedness).
• Alcohol: Excess alcohol can worsen hypotension and impair erectile response.
• Other ED therapies/PDE5 inhibitors: Do not combine.
• Warfarin/aspirin: No clinically meaningful PK/PD interaction observed, but use caution in patients with bleeding risk.

Frequently Asked Questions (FAQ)

Will VIGOREX® give me an erection automatically?
No. It enhances the natural erectile response and works only with sexual stimulation.

How fast does it work and for how long?
Onset is typically 30–60 minutes (faster on an empty stomach). The effect window is about 4 hours, though this varies by individual.

Can I take it with food or alcohol?
Food, especially high-fat meals, can delay onset. Limit alcohol as it can increase dizziness and reduce erectile performance.

Is it safe to buy VIGOREX® online without a prescription?
No. Counterfeit products are common and potentially dangerous. Always use a licensed pharmacy with a valid prescription.

References

1. U.S. FDA Prescribing Information (Viagra – Sildenafil): Pharmacology, dosing, interactions, and safety (latest label).
2. European Medicines Agency (EMA) – Sildenafil SmPC: Summary of product characteristics and clinical pharmacology.
3. British National Formulary (BNF): Erectile dysfunction treatments, dosing guidance, cautions, and interactions.
4. Product Information: Internal leaflet from SIGMA (local brand details and pack strengths).