Is tadalafil (phosphodiesterase type 5 inhibitor) safe to use in patients with ocular myasthenia gravis?

Safety of Tadalafil in Ocular Myasthenia Gravis

Tadalafil is generally safe for use in patients with ocular myasthenia gravis, but caution is warranted due to potential risks of worsening visual symptoms in some patients.

Mechanism and Safety Considerations

Tadalafil, a phosphodiesterase type 5 inhibitor (PDE5I), has no specific contraindication for use in myasthenia gravis according to current guidelines. However, several important safety considerations should guide its use:

Primary Safety Concerns

• Visual Effects: Tadalafil is contraindicated in patients who report sudden loss of vision due to anterior ischemic optic neuropathy after previous use of PDE5Is 1. This is particularly relevant for ocular myasthenia gravis patients who already have visual disturbances.

• Cardiovascular Considerations: The most important contraindication is concomitant use with nitrate medications due to risk of severe hypotension 1. Tadalafil should not be used in patients with:

  • Cardiac disease
  • Hypotension
  • Poorly controlled blood pressure
  • Recent stroke (within 6 months)
  • Significant hepatic or renal insufficiency 1

Specific to Myasthenia Gravis

• No direct evidence suggests tadalafil worsens myasthenic symptoms in ocular myasthenia gravis patients.

• The American Society of Clinical Oncology (ASCO) guidelines for immune-related adverse events mention myasthenia gravis management but do not list PDE5Is among medications that worsen myasthenia 1.

• The medications specifically noted to worsen myasthenia gravis include:

  • β-blockers
  • IV magnesium
  • Fluoroquinolones
  • Aminoglycosides
  • Macrolides 1

Clinical Approach

When considering tadalafil for a patient with ocular myasthenia gravis:

1. Assess disease stability: Ensure the myasthenia is well-controlled before initiating tadalafil.

2. Review current medications: Check for contraindicated medications, especially nitrates.

3. Monitor closely: After initiating tadalafil, monitor for:

   • Worsening of ocular symptoms (ptosis, diplopia, extraocular movement abnormalities)
   • Cardiovascular effects (blood pressure changes)
   • Common side effects: flushing, gastro-esophageal reflux, headache, dyspepsia, back pain, and nasal congestion 1

4. Discontinue if necessary: If worsening of myasthenic symptoms occurs, discontinue tadalafil and reassess.

Special Considerations

• Long half-life: Tadalafil has a half-life of 17.5 hours, which is significantly longer than other PDE5Is. Patients should avoid taking nitroglycerin for ≥48 hours after tadalafil use 1.

• Ocular symptoms: Since ocular myasthenia gravis primarily affects the extraocular muscles causing ptosis and diplopia 1, 2, any medication that could potentially impact vision should be used with caution.

• Treatment monitoring: Regular follow-up with both neurology and ophthalmology is recommended to monitor disease stability and medication effects.

Conclusion

While there is no specific contraindication to using tadalafil in patients with ocular myasthenia gravis, careful monitoring is essential, particularly for any worsening of ocular symptoms. The standard contraindications for tadalafil use still apply, with special attention to cardiovascular status and concomitant medications.