Saxenda (liraglutide 3.0 mg) is a GLP-1 receptor agonist licensed in the UK for weight management in adults with obesity or overweight with comorbidities. Patients with myasthenia gravis—a chronic autoimmune neuromuscular disorder causing muscle weakness—require careful consideration when starting any new medication. Whilst Saxenda is not contraindicated in myasthenia gravis, limited clinical data exist regarding its safety in this population. This article examines the relationship between Saxenda and myasthenia gravis, exploring safety considerations, monitoring requirements, and alternative weight management strategies for patients with this neuromuscular condition.

Understanding Saxenda and Its Mechanism of Action

Saxenda (liraglutide 3.0 mg) is a prescription medicine licensed in the UK for weight management in adults with obesity (BMI ≥30 kg/m²) or overweight (BMI ≥27 kg/m²) with at least one weight-related comorbidity, such as type 2 diabetes, hypertension, dyslipidaemia, obstructive sleep apnoea or prediabetes. It is also licensed for weight management in adolescents aged 12-17 years with obesity and body weight above 60 kg. Saxenda is administered as a once-daily subcutaneous injection and is intended to be used alongside a reduced-calorie diet and increased physical activity.

Liraglutide belongs to a class of medications known as glucagon-like peptide-1 (GLP-1) receptor agonists. It works by mimicking the action of the naturally occurring hormone GLP-1, which is released from the intestine in response to food intake. The mechanism of action involves several pathways that contribute to weight loss. Firstly, liraglutide acts on receptors in the brain's appetite centres, particularly in the hypothalamus, to reduce hunger and increase feelings of fullness (satiety). Secondly, it slows gastric emptying, which prolongs the sensation of fullness after meals. Additionally, GLP-1 receptor agonists enhance glucose-dependent insulin secretion and suppress inappropriate glucagon release, which can help improve glycaemic control in patients with type 2 diabetes. It's important to note that Saxenda 3.0 mg is specifically licensed for weight management and not for the treatment of type 2 diabetes.

The medication is typically initiated at a low dose (0.6 mg daily) and gradually increased over several weeks to the maintenance dose of 3.0 mg daily, as detailed in the Summary of Product Characteristics (SmPC). This titration schedule helps minimise gastrointestinal side effects, which are among the most common adverse reactions. Saxenda is regulated by the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK and is available only on prescription. According to the SmPC, treatment should be discontinued if patients do not achieve at least 5% weight loss after 12 weeks on the 3.0 mg daily dose.

Myasthenia Gravis: Overview and Treatment Considerations

Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disorder characterised by weakness and rapid fatigue of voluntary muscles. The condition occurs when the immune system produces antibodies that block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction, preventing muscle contraction. In the UK, myasthenia gravis affects approximately 15 per 100,000 people, with women more commonly affected before age 40 and men more frequently diagnosed after age 60.

The hallmark symptoms of myasthenia gravis include fluctuating muscle weakness that typically worsens with activity and improves with rest. Commonly affected muscle groups include those controlling eye and eyelid movement (causing ptosis and diplopia), facial expression, chewing, swallowing, and speech. In more severe cases, weakness can affect the respiratory muscles, leading to myasthenic crisis—a life-threatening emergency requiring immediate medical intervention and mechanical ventilation.

Treatment of myasthenia gravis typically involves a combination of approaches. Acetylcholinesterase inhibitors (such as pyridostigmine) are often first-line symptomatic treatments that increase the availability of acetylcholine at the neuromuscular junction. Many patients also require immunosuppressive therapy, including corticosteroids, azathioprine, mycophenolate mofetil, or other agents to reduce antibody production. Thymectomy may be considered in selected patients, particularly those with thymoma or acetylcholine receptor antibody-positive generalised MG, with decisions made on an individualised basis by specialists.

Patients with myasthenia gravis require careful consideration when prescribing new medications, as certain drugs can exacerbate muscle weakness or precipitate myasthenic crisis. Medications known to worsen MG include some antibiotics (particularly aminoglycosides, fluoroquinolones, and macrolides), beta-blockers, certain anaesthetic agents, magnesium salts, quinine derivatives, antipsychotics, and neuromuscular blocking drugs. Healthcare professionals should consult reliable UK sources such as the BNF or specialist neurology guidance before prescribing any new medication for patients with MG.

Safety Profile of Saxenda in Patients with Myasthenia Gravis

The relationship between Saxenda and myasthenia gravis is not extensively documented in clinical literature, and there is no official established link between liraglutide use and worsening of myasthenia gravis symptoms. The Summary of Product Characteristics (SmPC) for Saxenda, as approved by the European Medicines Agency (EMA) and MHRA, does not list myasthenia gravis as a contraindication or specific precaution. However, this does not automatically mean the medication is entirely without risk in this patient population, as clinical trial data for Saxenda specifically in patients with myasthenia gravis are limited.

The most commonly reported adverse effects of Saxenda include gastrointestinal symptoms such as nausea, vomiting, diarrhoea, and constipation, which occur in a significant proportion of patients, particularly during dose escalation. Other notable side effects include injection site reactions, headache, dyspepsia, and fatigue. More serious adverse effects include pancreatitis, gallbladder disease, increased heart rate, and potential thyroid C-cell tumours (observed in rodent studies but not conclusively demonstrated in humans).

Important safety considerations from the SmPC include:

• Treatment should be stopped immediately if pancreatitis is suspected (persistent, severe abdominal pain, sometimes radiating to the back, with or without vomiting)

• Patients should be counselled about the risk of gallbladder disease and advised to report symptoms such as right upper quadrant pain, fever or jaundice

• Risk of acute kidney injury secondary to dehydration from severe gastrointestinal side effects

• Increased risk of hypoglycaemia when used with sulfonylureas or insulin in people with type 2 diabetes

• Potential effects on absorption of oral medicines due to delayed gastric emptying (e.g., warfarin may require additional INR monitoring)

• Saxenda is contraindicated in pregnancy and not recommended during breastfeeding

For patients with myasthenia gravis, particular attention should be paid to any medication-related effects that could indirectly impact their condition. For example, severe gastrointestinal side effects leading to dehydration or electrolyte imbalances could theoretically affect neuromuscular function. Additionally, fatigue—a common side effect of Saxenda—may be difficult to distinguish from myasthenia-related fatigue, potentially complicating symptom monitoring.

Given the absence of specific safety data, a cautious, individualised approach is warranted when considering Saxenda for weight management in patients with myasthenia gravis. Healthcare professionals should conduct a thorough risk-benefit assessment, considering the severity of the patient's MG, their current treatment regimen, disease stability, and the clinical need for weight management intervention. Patients should be advised to report any suspected side effects via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).

Clinical Considerations and Monitoring Requirements

When considering Saxenda for a patient with myasthenia gravis, several clinical considerations should guide decision-making. Firstly, the prescribing clinician should establish close communication with the patient's neurologist or specialist managing their myasthenia gravis. This multidisciplinary approach ensures that all healthcare providers are aware of the treatment plan and can monitor for any potential interactions or complications.

Before initiating Saxenda, a comprehensive baseline assessment should include documentation of the patient's current MG symptoms, disease severity (using standardised scales such as the Myasthenia Gravis Foundation of America classification), current medications (including immunosuppressants and acetylcholinesterase inhibitors), and recent disease stability. It is advisable to ensure that the patient's myasthenia gravis is well-controlled and stable before introducing a new medication that could potentially complicate symptom assessment.

Monitoring during treatment should be more frequent than in patients without myasthenia gravis. Patients should be advised to report any new or worsening muscle weakness, difficulty swallowing, breathing difficulties, or changes in their usual MG symptoms immediately. Regular follow-up appointments should assess both weight management progress and any changes in neuromuscular function. Monitoring should include weight, gastrointestinal tolerance, hydration status, heart rate, and renal function if significant gastrointestinal losses occur. For patients with type 2 diabetes, blood glucose monitoring is essential, especially if they are also taking insulin or sulfonylureas.

Healthcare professionals should maintain a low threshold for discontinuing Saxenda if there is any concern about worsening myasthenic symptoms, even if a direct causal relationship is uncertain. Treatment should also be stopped immediately if pancreatitis is suspected, and patients should be advised to report symptoms of gallbladder disease promptly.

Patients should be educated about the common side effects of Saxenda and how to distinguish these from potential MG-related symptoms. For instance, fatigue from Saxenda typically improves over time, whereas MG-related fatigue characteristically worsens with activity and improves with rest. Clear written information should be provided about when to seek urgent medical attention, particularly for signs of myasthenic crisis (severe weakness, respiratory difficulty, or choking). Patients should be explicitly advised to call 999 or attend A&E immediately if they experience severe breathing difficulty, rapidly worsening bulbar weakness, or suspected myasthenic crisis.

Additionally, attention should be paid to maintaining adequate hydration and nutrition, as gastrointestinal side effects from Saxenda could potentially affect the absorption or timing of MG medications, particularly pyridostigmine, which requires consistent dosing schedules for optimal symptom control.

Alternative Weight Management Options for Myasthenia Gravis Patients

For patients with myasthenia gravis who require weight management but for whom Saxenda may not be suitable, several alternative approaches should be considered. NICE guidance on obesity management (CG189) emphasises a multicomponent approach that does not rely solely on pharmacological intervention.

Dietary modification remains the cornerstone of weight management and can be safely implemented in patients with myasthenia gravis. Referral to a registered dietitian with experience in neuromuscular conditions is valuable, as they can develop an individualised eating plan that addresses both weight management goals and the specific challenges faced by MG patients, such as dysphagia or fatigue affecting meal preparation. A modest calorie deficit (typically 500-600 kcal/day) combined with adequate protein intake to preserve muscle mass is generally recommended. Patients with swallowing difficulties may benefit from texture-modified diets that are both safe and nutritionally adequate.

Physical activity should be carefully tailored to the individual's functional capacity and MG severity. Whilst exercise is beneficial for weight management and overall health, patients with myasthenia gravis must avoid overexertion, which can trigger or worsen symptoms. A physiotherapist experienced in neuromuscular conditions can design an appropriate exercise programme that respects the patient's limitations whilst promoting gradual fitness improvements. Low-impact activities such as swimming (with appropriate supervision), gentle cycling, or chair-based exercises may be suitable options. Activity should be planned for times when MG symptoms are typically better controlled (often earlier in the day or after medication doses).

Alternative pharmacological options may be considered in consultation with specialists. Semaglutide 2.4 mg (Wegovy) has been approved by NICE for weight management in adults with obesity or overweight with weight-related comorbidities, though similar cautions would apply as with Saxenda due to limited data in MG patients. Orlistat, a lipase inhibitor that reduces fat absorption, has a different mechanism of action to GLP-1 receptor agonists and may be appropriate for some patients, though gastrointestinal side effects should be considered. For patients with type 2 diabetes and myasthenia gravis, certain diabetes medications such as metformin or SGLT2 inhibitors may provide modest weight loss benefits alongside their primary indication for glycaemic control, though individual assessment is essential.

Psychological support through cognitive behavioural therapy or other evidence-based interventions can address emotional eating, motivation, and the psychological challenges of managing multiple chronic conditions. Tier 3 specialist weight management services, available through NHS referral pathways, can provide intensive multidisciplinary support tailored to complex patients.

In cases of severe obesity where conservative measures have been unsuccessful, bariatric surgery may be considered, though this requires particularly careful evaluation in patients with myasthenia gravis due to anaesthetic risks and the potential impact of rapid weight loss on muscle mass and overall condition stability. Such decisions should only be made within specialist multidisciplinary team settings with expertise in both bariatric surgery and neuromuscular disorders, following NHS Tier 4 weight management service pathways.

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