Metronidazole Suppository
Metronidazole suppositories provide localized delivery of this potent nitroimidazole antibiotic for treating vaginal and rectal infections. These pessaries offer targeted therapy with minimal systemic absorption, reducing side effects while maintaining high tissue concentrations. Clinically proven effective against bacterial vaginosis, trichomoniasis, and anaerobic rectal infections, the suppository form is ideal for patients who cannot tolerate oral metronidazole. The medication works by disrupting microbial DNA synthesis in susceptible organisms. Treatment typically involves once or twice-daily insertion for 5-7 days, with symptom relief often occurring within 48 hours.
Metronidazole suppositories deliver distinct advantages over oral formulations. They achieve 10-20x higher local drug concentrations with 90% lower systemic exposure, minimizing nausea and metallic taste side effects. The suppositories are first-line treatment for bacterial vaginosis (85-90% cure rates) and effective against trichomoniasis when oral therapy isn't feasible. Their rectal form treats anaerobic proctitis and prevents postoperative infections in colorectal surgery. Recent studies show efficacy in managing pelvic inflammatory disease when combined with other antibiotics. The localized action makes them particularly valuable for pregnant patients needing to minimize fetal drug exposure.
Vaginal suppositories should be inserted high in the vaginal vault using the provided applicator, ideally at bedtime to enhance retention. Rectal suppositories require insertion past the internal sphincter (about 1 inch in adults). Patients should remain recumbent for 30 minutes post-insertion. Standard dosing is 500mg once daily (vaginal) or 1g twice daily (rectal). Hands must be washed before and after administration. Concurrent use with vaginal products (tampons, douches) should be avoided. Treatment continues for the full prescribed duration even if symptoms resolve earlier to prevent recurrence and antibiotic resistance.
While oral metronidazole achieves systemic coverage for disseminated infections, suppositories offer superior local efficacy with fewer side effects. The suppository form avoids first-pass metabolism, requiring lower total doses for equivalent local effect. Patients report 60% fewer gastrointestinal complaints with vaginal suppositories versus oral tablets. However, suppositories don't treat extra-pelvic infections and may be less convenient for some users. Cost comparisons show similar pricing, though suppositories eliminate the need for alcohol avoidance required with oral therapy. The choice depends on infection location, patient preference, and tolerability factors.
Local reactions occur in 5-10% of users, including vaginal/rectal irritation, discharge, or mild burning. Systemic absorption may still cause headache (3% of patients) or dark urine (harmless metabolite). Rare but serious risks include allergic reactions and peripheral neuropathy with prolonged use. Contraindications include first-trimester pregnancy (vaginal form) and hypersensitivity to nitroimidazoles. Drug interactions include potentiation of warfarin effect and disulfiram-like reactions if alcohol is consumed (though risk is lower than with oral therapy). Patients should report severe irritation or neurological symptoms immediately.
Second/third-trimester pregnant patients may use vaginal suppositories when benefits outweigh risks. Nursing mothers should discard breast milk for 24 hours post-treatment. Pediatric use is limited to rectal form for anaerobic infections in children >12 years. Elderly patients require no dose adjustment but may need assistance with proper insertion. Immunocompromised patients should be monitored for secondary fungal infections. Those with hepatic impairment metabolize the small absorbed fraction more slowly, though dosage adjustment is rarely needed for suppository therapy.
Metronidazole suppositories work through intracellular reduction of their nitro group, creating cytotoxic compounds that disrupt microbial DNA and inhibit nucleic acid synthesis. The medication is selectively activated by anaerobic organisms and protozoa, explaining its potency against Gardnerella vaginalis (bacterial vaginosis), Trichomonas vaginalis, and Clostridial species. Vaginal epithelium absorbs 20-30% of the dose, maintaining tissue concentrations above MIC90 for 24 hours post-insertion. Rectal administration achieves effective luminal levels against anaerobic flora while minimizing systemic exposure. This targeted action preserves normal vaginal lactobacilli better than broad-spectrum alternatives.
Strongest evidence supports metronidazole suppositories for: bacterial vaginosis (7-day vaginal regimen achieves 88% cure rate), as adjuvant therapy for pelvic inflammatory disease, and prevention of postoperative anaerobic infections in colorectal surgery. The vaginal form shows 70-75% efficacy against trichomoniasis when oral therapy is contraindicated. Recent studies demonstrate value in managing radiation proctitis and antibiotic-associated pseudomembranous colitis via rectal administration. Off-label uses include treatment of vaginal aerobic vaginitis when combined with other agents. Treatment success is confirmed by resolution of symptoms and (when appropriate) follow-up pH testing or microscopy.
Metronidazole suppositories require refrigeration (2-8°C) to maintain stability, though some formulations tolerate room temperature for limited periods. Patients should check for melting or discoloration before use. The foil packaging protects from light degradation until administration. Unused suppositories remain potent until the expiration date if stored properly. Travelers may use insulated containers for short-term transport. Pharmacists should counsel patients on proper storage to ensure medication efficacy throughout the treatment course. Improperly stored suppositories may lose potency or become difficult to administer.
Generic metronidazole suppositories cost $30-$80 per treatment course, comparable to oral therapy. Most insurance plans cover FDA-approved indications, though prior authorization may be required for off-label uses. The vaginal form is included on the WHO Essential Medicines List, ensuring availability in public health systems globally. Some manufacturers offer patient assistance programs. Cost-effectiveness analyses favor suppositories over oral therapy for bacterial vaginosis due to reduced treatment failures and side effects. The rectal form proves particularly cost-effective for preventing expensive postoperative infections in colorectal surgery.
Patients require instruction on proper insertion technique, emphasizing hand hygiene and complete dosage administration. They should understand that vaginal discharge may temporarily increase and that sexual intercourse should be avoided during treatment. The importance of completing the full course despite symptom resolution must be stressed. Users should recognize signs of allergic reaction (itching, swelling) and potential drug interactions. Counseling should address proper storage and disposal of unused medication. Follow-up timing for test-of-cure (when applicable) should be clearly communicated to prevent recurrence or complications.
Current studies investigate: bioadhesive vaginal gels for extended release, combination suppositories with antifungals for mixed infections, and lower-dose regimens to further reduce systemic exposure. Phase III trials are evaluating a novel rectal foam formulation for ulcerative proctitis. Research continues on metronidazole's potential immunomodulatory effects in chronic pelvic inflammatory conditions. These advancements aim to enhance localized delivery while expanding therapeutic applications for this well-established antibiotic.
These 500mg vaginal/rectal suppositories treat: bacterial vaginosis (BV), trichomoniasis, anaerobic pelvic infections, and post-surgical prophylaxis. The local delivery provides high tissue concentrations with minimal systemic absorption.
• Vaginal use: Insert 1 suppository at bedtime for 5-7 consecutive days
• Rectal use: Insert 500mg every 8-12 hours for anaerobic infections
• Wash hands before/after insertion
• Use provided applicator or finger (with glove)
• Remain lying down for 30 minutes post-insertion
• Continue during menstruation
Suppositories offer:
• 90% lower systemic absorption (reduced side effects)
• Direct infection site targeting
• Bypass first-pass metabolism
• Safe for patients with GI intolerance
• No alcohol interaction risk at this dose
This high-concentration formulation:
• Achieves therapeutic levels in 2-3 doses
• Allows once-daily vaginal administration
• Maintains effective concentrations between doses
• Reduces treatment duration by 50% vs lower strengths
Category B: Vaginal suppositories are preferred over oral for BV in pregnancy (2nd/3rd trimester). Systemic absorption is minimal, avoiding fetal exposure. Rectal use requires risk-benefit assessment.
1. Discontinue if severe mucosal irritation occurs
2. May cause metallic taste (less common than oral)
3. Risk of vaginal candidiasis post-treatment
4. Temporary dark urine (harmless metabolite)
5. Avoid concurrent use with blood thinners
• BV symptom relief: 2-3 days
• Discharge normalization: 5-7 days
• Complete microbial eradication: 7-10 days
• Maximum efficacy requires completing full course
• Recurrence rate: 15-30% at 3 months
• Keep refrigerated (2-8°C) until use
• Brief room temperature storage (<1 week) acceptable
• Protect from moisture and heat
• Do not freeze
• Check for melting before insertion
• Warfarin: Increased bleeding risk
• Lithium: Elevated serum levels
• Disulfiram: Psychotic reactions
• Alcohol: Avoid excessive consumption (minimal risk with suppositories)
• CYP3A4 substrates: Altered metabolism
Intercourse can: dislodge the suppository, reintroduce pathogens, and increase irritation. Complete abstinence (including sex toys) until 24 hours after final dose optimizes cure rates.