Guanfacine (Intuniv) is a non-stimulant medication licensed in the UK for treating ADHD in children and adolescents aged 6–17 years. Whilst erectile dysfunction is not listed as a common side effect in the UK Summary of Product Characteristics, some patients and clinicians have raised concerns about potential sexual side effects. This article examines the evidence on whether guanfacine causes erectile dysfunction, explores the mechanisms by which it might affect sexual function, and provides practical guidance on what to do if you experience sexual difficulties whilst taking this medication. Understanding the relationship between guanfacine and erectile function is important for informed treatment decisions and open discussions with your GP.

What Is Guanfacine and How Does It Work?

Guanfacine is a selective alpha-2A adrenergic receptor agonist licensed in the UK for the treatment of attention deficit hyperactivity disorder (ADHD) in children and adolescents aged 6–17 years, as part of a comprehensive treatment programme. It is marketed under the brand name Intuniv and is typically prescribed when stimulant medications are unsuitable, ineffective, or not tolerated, in line with NICE guidance (NG87). Guanfacine is not licensed for adults in the UK; any adult use is off-label and usually initiated by a specialist under shared-care arrangements.

The medication works by stimulating post-synaptic alpha-2A adrenergic receptors in the prefrontal cortex of the brain, an area crucial for attention, impulse control, and executive function. This action improves executive function and reduces sympathetic nervous system outflow, which can lower heart rate and blood pressure. Unlike stimulant medications such as methylphenidate, guanfacine does not increase dopamine levels directly, which accounts for its different side effect profile.

Guanfacine is administered as a modified-release tablet, usually taken once daily at the same time each day. Tablets should be swallowed whole and must not be crushed or chewed. The dose is typically started low and gradually increased under medical supervision to minimise adverse effects, particularly cardiovascular changes such as hypotension and bradycardia. Common side effects include somnolence, fatigue, headache, abdominal pain, and dry mouth. Because guanfacine affects the autonomic nervous system, it can influence various physiological processes beyond the central nervous system, including cardiovascular and sexual function.

Patients prescribed guanfacine should have their blood pressure and heart rate monitored at baseline, after each dose adjustment, and periodically thereafter, as recommended in the UK Summary of Product Characteristics (SmPC). Important interactions include strong or moderate CYP3A4 inhibitors and inducers, which can alter guanfacine levels; patients should also avoid grapefruit juice, which increases guanfacine exposure. It is important not to stop guanfacine abruptly, as this can lead to rebound hypertension and other withdrawal symptoms. If you experience any side effects, you can report them via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or through the Yellow Card app.

Why Might Guanfacine Affect Sexual Function?

Erectile dysfunction is not listed as a common or very common adverse reaction in the UK Summary of Product Characteristics (SmPC) for Intuniv. Evidence on sexual adverse effects with guanfacine is limited, in part because clinical trials have focused on paediatric populations; adult data are mainly derived from post-marketing surveillance and observational reports. Patients and clinicians should consult the current UK SmPC and European Medicines Agency (EMA) European Public Assessment Report (EPAR) for the most up-to-date safety information.

Nevertheless, there is a theoretical basis for why guanfacine might influence sexual function. As an alpha-2A adrenergic agonist, guanfacine reduces sympathetic nervous system activity, resulting in lowered blood pressure and heart rate. Erectile function depends on adequate blood flow to the penile tissues, which is regulated by a complex interplay between the sympathetic and parasympathetic nervous systems. Any medication that significantly alters cardiovascular dynamics or autonomic tone has the potential to affect erectile function, though the clinical significance of this effect with guanfacine remains uncertain and is not established in controlled trials.

Additionally, some of the more common side effects of guanfacine—such as fatigue, somnolence, and sedation—may indirectly impact sexual desire and performance. Reduced energy levels and persistent tiredness can diminish libido and make sexual activity less appealing or physically feasible. Psychological factors, including mood changes or anxiety related to ADHD or its treatment, may also contribute to sexual difficulties.

It is important to note that if erectile dysfunction occurs during guanfacine treatment, other contributing factors—such as underlying cardiovascular or metabolic conditions, psychological stress, or concomitant medications—should also be considered and assessed by your GP.

What to Do If You Experience Erectile Dysfunction on Guanfacine

If you develop erectile dysfunction or other sexual difficulties while taking guanfacine, it is essential to discuss this openly with your GP or prescribing clinician. Sexual health concerns are a legitimate medical issue and should be addressed without embarrassment or delay. Your doctor will take a thorough history to determine whether the symptom is likely related to guanfacine or may have alternative causes.

Key steps your clinician may take include:

• Reviewing your medication history: Your GP will assess all medications you are taking, as some drugs—including antihypertensives, antidepressants, and antipsychotics—are known to affect sexual function. Polypharmacy or drug interactions may contribute to erectile dysfunction.

• Assessing cardiovascular and metabolic health: Erectile dysfunction can be an early indicator of cardiovascular disease, diabetes, or other systemic conditions. Your doctor may check your blood pressure, fasting blood glucose or HbA1c, lipid profile, and, if features of hypogonadism are present, morning total testosterone levels, in line with NICE Clinical Knowledge Summaries (CKS) guidance on erectile dysfunction.

• Evaluating psychological factors: Stress, anxiety, depression, and relationship difficulties can all contribute to sexual dysfunction. ADHD itself is associated with higher rates of mood disorders, which may independently affect sexual health.

• Considering dose adjustment or medication review: If guanfacine is suspected to be contributing to erectile dysfunction, your doctor may consider adjusting the dose or exploring alternative ADHD treatments. However, you should never stop or alter your guanfacine dose without medical advice, as abrupt discontinuation can cause rebound hypertension and other withdrawal effects.

In some cases, your GP may refer you to a specialist, such as a urologist or sexual health clinic, for further assessment. Treatment options for erectile dysfunction—such as phosphodiesterase-5 (PDE5) inhibitors (e.g., sildenafil)—may be considered if appropriate. However, PDE5 inhibitors can lower blood pressure and, when combined with guanfacine, may increase the risk of dizziness or syncope. If a PDE5 inhibitor is prescribed, your doctor will start at the lowest effective dose and review your blood pressure carefully. PDE5 inhibitors must not be used if you are taking nitrates (e.g., glyceryl trinitrate) or riociguat, and caution is required if you are on alpha-blockers.

Seek urgent medical help (call 999 or attend A&E) if you experience:

• Chest pain, particularly on exertion

• Collapse or fainting (syncope)

• Severe breathlessness or palpitations

Alternative Treatments and When to Speak to Your GP

If erectile dysfunction persists or significantly affects your quality of life, discussing alternative ADHD treatments with your GP or psychiatrist may be appropriate. Several medication options are available in the UK, each with distinct mechanisms of action and side effect profiles.

Stimulant medications, such as methylphenidate (e.g., Concerta XL, Medikinet XL) and lisdexamfetamine (Elvanse), are first-line treatments for ADHD according to NICE guideline NG87. While stimulants can cause side effects such as appetite suppression, insomnia, and increased heart rate, sexual dysfunction is not commonly reported. However, individual responses vary, and some patients may experience reduced libido or other sexual side effects with stimulants.

Atomoxetine (Strattera) is a non-stimulant alternative that works as a selective noradrenaline reuptake inhibitor. It is licensed for ADHD in children, adolescents, and adults and is recommended by NICE as a second-line option. Sexual side effects, including erectile dysfunction and decreased libido, are recognised adverse reactions in the UK SmPC for atomoxetine, so this may not be a suitable alternative if sexual function is a primary concern.

Non-pharmacological interventions should also be considered as part of a comprehensive ADHD management plan. Cognitive behavioural therapy (CBT), psychoeducation, and organisational skills training can be effective adjuncts or alternatives to medication, particularly for adults with ADHD, as recommended by NICE.

When to contact your GP:

• If erectile dysfunction develops suddenly or worsens significantly

• If you experience other concerning symptoms, such as chest pain, severe dizziness, or fainting

• If sexual difficulties are affecting your mental health or relationships

• If you are considering stopping or changing your medication

Your GP can provide a holistic assessment, balancing the benefits of ADHD treatment with your overall health and quality of life. Open communication about sexual health is essential to ensure you receive appropriate, individualised care. Remember, you can report any suspected side effects via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or through the Yellow Card app.

Frequently Asked Questions