Sixmo – A Long-Acting Implant for Opioid Dependence

What Is Sixmo?

Sixmo is a buprenorphine hydrochloride implant designed as a long-lasting substitution treatment for opioid dependence. It is intended for clinically stable adult patients requiring a daily dose of no more than 8 mg of sublingual buprenorphine. The implant must be used alongside comprehensive medical, social, and psychological support.European Medicines Agency (EMA)European Pharmaceutical Review

How It Works

Sixmo comprises four small rods implanted under the skin of the upper arm under local anesthesia. These rods continuously release buprenorphine over six months, offering a steady dose while reducing the need for daily medication intake.European Pharmaceutical ReviewMedscape This sustained-delivery method helps improve treatment adherence, lower the risk of misuse, and prevents accidental ingestion, especially in household settings.European Pharmaceutical ReviewMedscape

Regulatory History

• CHMP Opinion Adopted: 26 April 2019European Medicines Agency (EMA)MDEdgeMedscape
• Marketing Authorisation Issued: 19 June 2019European Medicines Agency (EMA)efim.org
• Marketing Authorisation Withdrawn: 19 June 2025European Medicines Agency (EMA)

The centralised authorisation was held by L. Molteni & C. dei Fratelli Alitti Società di Esercizio S.p.A., based in Florence, Italy.European Medicines Agency (EMA)

Efficacy & Safety Profile

Clinical Trials & Effectiveness

Three pivotal trials involving 626 adult participants assessed Sixmo’s performance. In one key trial, 96.4% of patients responded to Sixmo compared to 87.6% on sublingual buprenorphine, demonstrating its potential superiority.MDEdgeEuropean Pharmaceutical Review Another study reported 96% of implant-treated patients remained free from illicit opioid use for at least four of the six months, compared to 88% treated with buprenorphine-naloxone sublingually (p=0.034).Scottish Medicines Consortium

Adverse Events

• Systemic side effects (typical of buprenorphine): headache, constipation, insomniaMDEdgeEuropean Pharmaceutical Review
• Implant-related reactions: pain, itching, hematoma at the insertion site; occasional breakages, infections, or expulsionsMDEdgeScottish Medicines ConsortiumEuropean Pharmaceutical Review
• Across trials, the rate of implant-site adverse events ranged from 14% to 58%, with fewer issues in later studies—likely due to improved implant techniques.Scottish Medicines Consortium

Long-term exposure (up to one year across continued trials) did not reveal new safety concerns.Scottish Medicines Consortium

Cost-Effectiveness & Health System Adoption

In Scotland, the Scottish Medicines Consortium (SMC) evaluated Sixmo and accepted its use within the NHS under a Patient Access Scheme (PAS)—which offered pricing concessions to improve cost-effectiveness.Scottish Medicines Consortium+1

Economic modeling indicated that Sixmo dominated (i.e., was both cheaper and more effective than) sublingual buprenorphine-naloxone in most base-case and sensitivity analyses. Notably:

• It reduced addiction clinic visits and pharmacy dispensing costs, contributing to overall savings.Scottish Medicines Consortium

However, the SMC cautioned that assumptions like reduced clinic visits might be overly optimistic, and the specific stable patient population and limited duration (up to one year) could restrict broader applicability.Scottish Medicines Consortium

Key Takeaways

Aspect	Details
Type of Treatment	Subcutaneous buprenorphine implant (4 rods), lasting 6 months
Indicated For	Clinically stable adults, ≤8 mg/day sublingual buprenorphine
Authorisation Timeline	CHMP opinion: 26 Apr 2019; EU approval: 19 Jun 2019; Withdrawal: 19 Jun 2025
Efficacy	96.4% response vs 87.6% (oral); 96% abstinence vs 88% control group
Side Effects	Implant site reactions; classic buprenorphine effects
Economic Insights	Cost-effective under specific pricing scheme; may reduce service utilization
Limitations	Narrow patient population; limited long-term data; surgical insert/remove

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