In view of the transdermal mode of delivery, an overdose of glyceryl trinitrate is unlikely to occur. However, in the unlikely event of an overdose, the symptoms could include the following:
• Fall in blood pressure ≤ 90 mmHg
• Collapse or syncope
• Paleness
• Sweating
• Weak pulse
• Reflex tachycardia
• Flushing
• Light-headedness on standing
• Headache
• Weakness
• Dizziness
• Nausea
• Vomiting
• Methaemoglobinaemia has been reported in patients receiving other organic nitrates. During glyceryl trinitrate biotransformation nitrite ions are released, which may induce methaemoglobinaemia and cyanosis with subsequent tachypnoea, anxiety, loss of consciousness and cardiac arrest. It can not be excluded that an overdose of glyceryl trinitrate may cause this adverse reaction
• In very high doses the intracranial pressure may be increased. This might lead to cerebral symptoms
General procedure:
• Since these patches are applied to the skin, removing the patch immediately stops delivery of the drug.
• General procedures in the event of nitrate-related hypotension
- Patient should be kept horizontal with the head lowered and legs raised or, if necessary, compression bandaging of the patient's legs.
- Supply oxygen
- Expand plasma volume
- For specific shock treatment admit patient to intensive care unit
Special procedure:
• Raising the blood pressure if the blood pressure is very low
• Treatment of methaemoglobinaemia
Treatment with intravenous methylene blue
- Initially 1 to 2 mg/kg, not exceeding 4 mg/kg of a 1% solution over 5 minutes.
- Repeat dose in 60 minutes if there is no response.
- Administer oxygen (if necessary)
- Initiate artificial ventilation
Treatment with methylene blue is contraindicated in patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency or methaemoglobin reductase deficiency. (see also section 4.4).
Where treatment with methylene blue is contraindicated or is not effective, exchange transfusion and / or transfusion of packed red blood cells is recommended.
Resuscitation measures:
In case of signs of respiratory and circulatory arrest, initiate resuscitation measures immediately.