Neostigmine Tablet Availability and Dosing for Myasthenia Gravis in the UK
Yes, neostigmine is available in tablet form (neostigmine bromide) in the UK and can be used as an alternative or adjunct to pyridostigmine for myasthenia gravis, with typical oral dosing ranging from 15-480 mg per day divided into multiple doses. 1
Dosing and Administration
Standard Oral Dosing
- Neostigmine bromide tablets are administered orally 2-4 times daily, similar to pyridostigmine dosing schedules 2
- The typical dose range is 15-480 mg per day, though this represents a wide therapeutic window that must be individualized based on symptom control 1
- For conversion from pyridostigmine: 30 mg oral pyridostigmine is approximately equivalent to 0.75 mg neostigmine IM or 1 mg IV, though oral-to-oral conversion ratios are less precisely defined 3
Clinical Context
- Neostigmine is often employed alongside pyridostigmine to help control symptoms in myasthenia gravis patients, functioning as adjuvant therapy rather than sole treatment 4
- Pyridostigmine remains the first-line acetylcholinesterase inhibitor (30 mg orally three times daily, gradually increased to maximum 120 mg four times daily), with neostigmine serving as an alternative when pyridostigmine alone is insufficient 5
Important Pharmacokinetic Consideration
A critical caveat: neostigmine may interfere with pyridostigmine bioavailability when both drugs are administered concurrently. 1 Studies demonstrate that while there is a direct relationship between pyridostigmine dose and plasma levels when used alone (r = 0.95), this relationship disappears when neostigmine is co-administered, suggesting potential drug-drug interaction affecting absorption or metabolism 1
Alternative Routes When Oral Administration Fails
Subcutaneous Infusion
- Neostigmine can be administered as a continuous subcutaneous infusion when enteral administration is no longer possible, particularly in end-of-life care or when swallowing is severely compromised 6
- This route has been successfully used to prevent myasthenic crisis in patients unable to take oral medications 6
Intranasal Administration
- Intranasal neostigmine provides rapid effect in 5-15 minutes and has been shown equally efficacious to oral pyridostigmine when substituted for morning doses 7
- This route is particularly beneficial for patients with irregular oral absorption, early morning weakness, bulbar impairment, or emergencies 7
- No significant side effects were noted even with 1 year of intranasal use 7
Critical Medication Avoidance
Patients on neostigmine or any acetylcholinesterase inhibitor for myasthenia gravis must avoid: beta-blockers, IV magnesium (absolutely contraindicated), fluoroquinolones, aminoglycosides, and macrolide antibiotics, as these can precipitate myasthenic crisis 3, 5, 2
Monitoring Requirements
- Regular pulmonary function assessment with NIF and VC measurements is essential, particularly for patients with moderate to severe generalized weakness 3
- The "20/30/40 rule" identifies respiratory failure risk: vital capacity <20 ml/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O 3
- Approximately 50% of patients with ocular myasthenia show minimal response to acetylcholinesterase inhibitors alone and may require escalation to corticosteroids 5, 2