Voluntary medication to manage sexual arousal could be rolled out across England and Wales by December 2028, potentially reaching thousands of male prisoners, according to an expert evaluating the programme. Prof Belinda Winder, who has assessed the use of sex drive-suppressing drugs in prisons, estimates that approximately one in four sex offenders – around 3,750 current prisoners – would be considered eligible for the treatment.
The government is expanding a pilot scheme known as the medication to manage problematic sexual arousal treatment pathway (MMPSA) from 10 to 20 prisons in November. According to the Ministry of Justice, approximately 6,400 sex offenders could access the medication alongside psychological support under the expanded scheme. The next phase will extend from the south-west of England into two additional NHS regions: the north-west and north-east.
The expansion comes as the government seeks to address prison overcrowding while managing sexual offences. About 15,000 prisoners in England and Wales are currently serving sentences for sexual offences, and more than 850 men are arrested each month on suspicion of online child sexual abuse offences. Government sources have indicated that the administration is keen to expand the voluntary use of these drugs as part of efforts to ease the prison capacity crisis.
What medications are being used?
The scheme targets sex offenders who experience intrusive, persistent and intense sexual thoughts, persistent arousal, and unhealthy sexual urges and behaviours. Prisoners can be offered selective serotonin reuptake inhibitors (SSRIs), such as sertraline, which help limit invasive sexual thoughts, and anti-androgens, which reduce testosterone production and limit libido. In some cases, anti-androgens reduce testosterone to pre-pubescent levels. A 2009 pilot at HMP Whatton marked the first UK use of this approach on a limited voluntary basis, with around 100 prisoners participating within a few years.
When could a national rollout happen?
Winder said the Ministry of Justice could be ready to launch the programme across prisons and probation services within 28 months if the pilot continues to progress successfully.
They [the Ministry of Justice] could be ready in December 2028 to roll the programme out if the interim findings look useful,she said. Those participating would need to receive clinical support to commit to taking the medication consistently and to avoid reoffending.
Winder expressed optimism about a properly resourced, voluntary national pathway.
A good national service needs appropriately trained clinicians, clear referral routes, appropriate psychological support alongside medication,she said. The expansion is being framed by the government as part of wider sentencing reform and prison-population reduction efforts.
Why is mandatory treatment being reconsidered?
Ministers are re-evaluating whether to proceed with a previous pledge to explore mandatory chemical castration of serious sex offenders, such as paedophiles and rapists. Two experts have told sources that a mandatory approach would not be effective. Winder raised significant concerns about compulsory treatment, noting that it would require screening a very large prison population to identify the much smaller group for whom treatment might actually be appropriate.
A mandatory approach would require screening a very large prison population to identify the much smaller group for whom treatment might actually be appropriate. It would have substantial clinical and resource implications,she said. Winder also warned of potential consequences including a breakdown of trust with offenders and risks of abuse.
Trying to impose and monitor daily medication among people who do not necessarily want to take it could be extremely inefficient. It could also introduce a range of consequences that we simply do not yet understand, including effects on trust, disclosure, engagement and the therapeutic relationship.
Winder rejected characterising the drugs as
chemical castration.
People say that because some people like the idea of castrating people who commit sexual offences. But these drugs are not permanent, unlike castration, and must be taken consistently to work.
How does this fit with early release policy?
The government has announced that prisoners convicted of rape, grooming and serious child sexual offences will be excluded from an early release scheme due to begin in October. Other sex offenders serving sentences of less than four years remain eligible for early release. This exclusion follows earlier warnings that some child sex offenders could still be eligible for early release, and reflects concerns from probation chiefs about the risks of mass early prisoner release.
What do the reoffending statistics show?
Sexual offenders have comparatively low reoffending rates compared with other prisoner cohorts. According to government data, 11.7% of sex offenders reoffended in 2023, compared with 53.9% of those with an index offence for theft. This lower rate suggests that targeted interventions may have measurable impact, though experts caution that long-term data on medication-based approaches remains limited.
What are the concerns about this approach?
Prison campaigners have urged caution before expanding the programme nationally. Critics have previously highlighted that long-term testosterone suppression can cause osteoporosis and cardiovascular disease. There is limited data available because randomised controlled trials remain scarce in this area.
Andrew Neilson, director of campaigns at the Howard League for Penal Reform, said:
The history of prison-based treatment programmes in this area has proven troubled, which is both a reason for exploring alternatives but also a reason to exercise caution before expanding new approaches more widely. It's also important that nobody is forced into these chemical interventions and that participation is truly voluntary.
Mark Fairhurst, national chair of the prison officers' union the POA, said:
Anything that potentially protects the public is welcome but I would be cautious about the rollout until we are in receipt of evidence that proves success.
What is the government's position?
A Ministry of Justice spokesperson said:
This government is determined to tackle the root causes of sex offending, which is why we're working at pace to extend the existing pilot to a further two regions.The expansion reflects recommendations from an independent sentencing review, which suggested that chemical castration
may assist in management of suitable sex offenders both in prison and in the community.
Key Facts
- The MMPSA pilot is expanding from 10 to 20 prisons in November, with approximately 6,400 sex offenders potentially able to access medication and psychological support
- Participation is entirely voluntary, and experts warn that mandatory approaches could damage trust and therapeutic relationships with offenders
- Sexual offenders have a reoffending rate of 11.7%, significantly lower than other prisoner cohorts, suggesting targeted interventions may be effective
- A national rollout could be possible by December 2028 if interim findings prove successful, according to experts evaluating the programme
- Long-term health risks including osteoporosis and cardiovascular disease have been identified as concerns, though randomised controlled trials remain limited
