Leech therapy for postherpetic neuralgia: a single-blind pilot trial
Mueller IM, Stange R, Michalsen A (2012) · Schmerz (Berlin, Germany) · n=28
RCT evidence detailTrial reference
GRADE LowCohort / case series
Study Profile
- Design
- single-center, single-blind (outcome assessor) pilot RCT (Berlin)
- Sample size (n)
- 28
- Intervention
- Single session of 3-5 Hirudo medicinalis leeches along the affected dermatome
- Comparator
- Topical capsaicin 0.075% cream applied 4 times daily for 28 days
- Primary endpoint
- Brief Pain Inventory (BPI) at day 28
- Primary result
- BPI pain score reduction 3.4 points in leech vs 1.6 in capsaicin at day 28 (between-group difference 1.8, p=0.04)
- Effect size (Cohen's d)
- 0.68
- Follow-up duration
- 8 weeks
Key Findings
- Outcome assessor blinded — improves on the typical open-label design
- Modest effect size (Cohen's d ≈ 0.68) consistent with refractory chronic pain context
- Tolerability favored leech — capsaicin caused burning sensation in 80% of users
- Effect sustained through 8 weeks
- First RCT data for hirudotherapy in a primarily neuropathic pain condition
Limitations
- Small sample (n=28)
- Single-blind only — clinician unblinded
- Single center
- Postherpetic neuralgia has notoriously high placebo response — single comparison may not control adequately
- No mechanistic biomarkers
Clinical Implications
Mueller 2012 is the only RCT data for hirudotherapy in a primarily neuropathic pain syndrome. The single-blind design is a methodological improvement on the German naturopathy series. For clinicians, the trial suggests cautious consideration in postherpetic neuralgia patients who have failed first-line treatments (gabapentin, pregabalin, tricyclic antidepressants). The evidence base remains limited and further trials are warranted.