Does lamictal cause erectile dysfunction? This question concerns many men prescribed lamotrigine (Lamictal) for epilepsy or bipolar disorder. Whilst the UK Summary of Product Characteristics lists decreased libido as an uncommon side effect, the evidence linking lamotrigine directly to erectile dysfunction remains limited. Unlike many psychotropic medications, lamotrigine does not significantly affect the hormonal or neurotransmitter pathways typically implicated in sexual dysfunction. However, the underlying conditions it treats—epilepsy and bipolar disorder—are themselves associated with higher rates of sexual difficulties. This article examines the evidence, explores potential mechanisms, and outlines practical management strategies for men experiencing erectile problems whilst taking lamotrigine.

What Is Lamictal and How Does It Work?

Lamotrigine (brand name Lamictal) is an anticonvulsant medication licensed in the UK for the treatment of epilepsy and bipolar disorder. It was initially developed to control seizures but has since become an important mood stabiliser, particularly for preventing depressive episodes in bipolar affective disorder. The Medicines and Healthcare products Regulatory Agency (MHRA) has approved lamotrigine for use in adults and children over the age of two for specific epilepsy types, and as maintenance treatment in bipolar disorder for patients aged 18 and over.

The mechanism of action of lamotrigine involves the stabilisation of neuronal membranes by blocking voltage-sensitive sodium channels. This action inhibits the release of excitatory neurotransmitters, particularly glutamate and aspartate, which play key roles in seizure generation and mood dysregulation. By dampening excessive neuronal firing, lamotrigine helps to prevent both seizures and mood episodes. Unlike many other mood stabilisers, lamotrigine has relatively minimal effects on other neurotransmitter systems, which contributes to its generally favourable side-effect profile.

Lamotrigine is typically initiated at a low dose and gradually titrated upwards over several weeks to reduce the risk of serious skin reactions, including Stevens-Johnson syndrome and drug reaction with eosinophilia and systemic symptoms (DRESS), which are most likely to occur within the first eight weeks of treatment. The maintenance dose varies depending on the indication and whether the patient is taking other medications that affect lamotrigine metabolism; for example, valproate inhibits lamotrigine metabolism (requiring lower doses), whilst enzyme-inducing drugs such as carbamazepine increase its clearance (requiring higher doses). Common side effects include headache, dizziness, drowsiness, insomnia, nausea, and skin rash. Serious adverse effects—including severe skin reactions, blood disorders, aseptic meningitis, haemophagocytic lymphohistiocytosis (HLH), and suicidal thoughts—are uncommon but require immediate medical attention. The drug is generally well-tolerated compared to older anticonvulsants and mood stabilisers.

For full prescribing information, see the MHRA/EMC Summary of Product Characteristics for lamotrigine, the BNF lamotrigine monograph, and the NHS medicines page for lamotrigine.

Why Might Lamictal Affect Sexual Function?

The relationship between lamotrigine and erectile dysfunction remains an area of clinical uncertainty. The UK Summary of Product Characteristics (SmPC) for lamotrigine lists decreased libido as an uncommon adverse effect, and some product documents include erectile dysfunction among post-marketing reports, though the frequency and causality are not well established. Unlike some other psychotropic medications—particularly selective serotonin reuptake inhibitors (SSRIs) and certain antipsychotics—lamotrigine does not significantly affect serotonergic, dopaminergic, or hormonal pathways typically implicated in sexual dysfunction. This pharmacological profile suggests that direct drug-induced erectile dysfunction would be uncommon, though it cannot be excluded.

Several indirect mechanisms may contribute to sexual difficulties in patients taking lamotrigine:

• Underlying psychiatric conditions: Both epilepsy and bipolar disorder are independently associated with higher rates of sexual dysfunction. Depression, in particular, commonly causes reduced libido, erectile difficulties, and anorgasmia. Anxiety about seizures or mood episodes can also impair sexual function.

• Polypharmacy effects: Many patients taking lamotrigine also receive other medications that are more clearly linked to erectile dysfunction, including antidepressants, antipsychotics, antihypertensives, and other anticonvulsants such as carbamazepine or valproate.

• Psychological factors: The stress of managing a chronic neurological or psychiatric condition, relationship difficulties, and concerns about medication side effects can all contribute to sexual problems.

• General side effects: Fatigue, dizziness, and cognitive effects occasionally reported with lamotrigine may indirectly affect sexual interest or performance.

Clinical studies specifically examining sexual function with lamotrigine monotherapy are limited. Some research suggests that lamotrigine may have a neutral or even potentially beneficial effect on sexual function compared to other mood stabilisers, particularly in women, though high-quality evidence is lacking. There is no robust evidence from controlled trials demonstrating a clear causal relationship between lamotrigine and erectile dysfunction in men.

For adverse effect information, see the MHRA/EMC SmPC for lamotrigine and the NHS medicines page for lamotrigine.

What to Do If You Experience Erectile Dysfunction on Lamictal

If you develop erectile dysfunction whilst taking lamotrigine, it is essential to discuss this with your GP or prescribing specialist rather than stopping the medication abruptly. Sudden discontinuation of lamotrigine can precipitate seizures in people with epilepsy or trigger mood episodes in those with bipolar disorder, potentially causing serious harm. Your healthcare provider can conduct a thorough assessment to identify the underlying cause and develop an appropriate management plan.

Initial assessment should include:

• A detailed medication review to identify other drugs that may contribute to erectile dysfunction

• Evaluation of the underlying psychiatric or neurological condition and its current control

• Assessment for other medical causes of erectile dysfunction, including cardiovascular disease, diabetes, hormonal imbalances (particularly testosterone deficiency), and lifestyle factors

• Discussion of psychological factors, relationship issues, and stress

• Physical examination and relevant investigations as indicated

Your doctor may arrange targeted blood tests based on your symptoms and risk factors, as recommended by NICE guidance. These may include HbA1c or fasting glucose, fasting lipid profile, and morning total testosterone (with repeat confirmation if borderline) if you have symptoms of low testosterone such as reduced libido, fatigue, or loss of muscle mass. Prolactin may be checked if clinically indicated. Cardiovascular risk assessment (for example, using QRISK) is particularly important, as erectile dysfunction can be an early marker of cardiovascular disease.

Management strategies may include:

• Optimising treatment of the underlying psychiatric or neurological condition, as improved mood and seizure control often enhance sexual function

• Reviewing and potentially adjusting other medications that may contribute to the problem

• Addressing modifiable lifestyle factors such as smoking, excessive alcohol consumption, obesity, and lack of physical activity

• Referral for psychological or relationship counselling if appropriate

• Consideration of specific treatments for erectile dysfunction, such as phosphodiesterase-5 (PDE5) inhibitors like sildenafil, which can be safely used alongside lamotrigine. Important: PDE5 inhibitors are contraindicated in men taking nitrates or riociguat and should be used with caution in those taking alpha-blockers (dose timing and monitoring may be required).

When to seek urgent medical advice: Contact your GP promptly if erectile dysfunction is accompanied by other concerning symptoms such as chest pain, severe mood changes, new neurological symptoms, or if you experience an erection lasting more than four hours (priapism, a medical emergency) or sudden loss of vision or hearing after taking erectile dysfunction medication.

Reporting side effects: If you suspect lamotrigine or any other medicine is causing side effects, you can report this via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or through the Yellow Card app.

For assessment and management guidance, see NICE Clinical Knowledge Summary: Erectile dysfunction, the BNF monographs for PDE5 inhibitors, and the NHS erectile dysfunction page.

Alternative Treatments and Management Options

If erectile dysfunction persists despite initial management strategies and is genuinely attributed to lamotrigine (after excluding other causes), your specialist may consider alternative mood stabilisers or anticonvulsants, though this decision must carefully balance the risks and benefits. Lamotrigine is often chosen specifically because of its favourable side-effect profile, and switching medications carries risks including loss of seizure control or mood destabilisation. Any change to antiepileptic or mood-stabilising medication must be undertaken under specialist supervision with careful cross-titration.

Alternative anticonvulsants for epilepsy include levetiracetam, which has a different mechanism of action and side-effect profile, or newer agents such as lacosamide or perampanel, depending on seizure type. For bipolar disorder, alternatives might include lithium (which requires regular blood monitoring), quetiapine, or in some cases, carefully monitored use of other anticonvulsants. Each alternative carries its own potential side effects, and some (particularly certain antipsychotics) may be more likely to cause sexual dysfunction than lamotrigine. Treatment choices should be guided by NICE guidance for epilepsy (NG217) and bipolar disorder (CG185).

Specific treatments for erectile dysfunction can often be used successfully alongside lamotrigine:

• PDE5 inhibitors (sildenafil, tadalafil, vardenafil) are first-line treatments for erectile dysfunction and have no known significant interactions with lamotrigine. Generic sildenafil is generally prescribable on the NHS; other PDE5 inhibitors may require Selected List Scheme (SLS) endorsement for NHS prescribing. Sildenafil 50 mg (Viagra Connect) is also available over the counter from pharmacies following a pharmacist assessment. Important: These medications are contraindicated in men taking nitrates or riociguat and should be used with caution in those taking alpha-blockers. Cardiovascular assessment may be required before treatment.

• Vacuum erection devices provide a non-pharmacological option and may be suitable for some patients.

• Intracavernosal injections or urethral suppositories may be considered for men who cannot use or do not respond to oral medications.

• Psychological interventions, including cognitive behavioural therapy (CBT) and sex therapy, can be highly effective, particularly when psychological factors contribute to the problem.

Lifestyle modifications remain important:

• Regular physical exercise improves cardiovascular health and erectile function

• Maintaining a healthy weight and managing conditions such as diabetes and hypertension

• Reducing alcohol intake and stopping smoking

• Stress management and adequate sleep

NICE guidance emphasises a holistic approach to managing erectile dysfunction, addressing physical, psychological, and relationship factors. Your GP can refer you to specialist services, including urology or sexual health clinics, if first-line treatments are unsuccessful. It is important to maintain open communication with your healthcare team and to continue your prescribed lamotrigine unless specifically advised otherwise by your doctor, as the benefits of seizure control or mood stabilisation typically outweigh potential sexual side effects that can often be managed effectively.

For treatment guidance, see NICE Clinical Knowledge Summary: Erectile dysfunction, BNF monographs for PDE5 inhibitors (including NHS prescribing status), NICE CG185 (Bipolar disorder), and NICE NG217 (Epilepsies in children, young people and adults).

Frequently Asked Questions