Potassium Channel Activators
Examples
Nicorandil
Indications
Angina - prophylaxis and treatment
Contraindications
Contraindications:
- Left ventricular failure with low filling pressure
- Hypotension
- Acute Pulmonary Oedema
- Breast feeding
- Hypovolaemia / hypotension
- Diverticular disease
- Pregnancy
Mechanism
Potassium channel activators work through two mechanisms. Firstly, they activate ATP-sensitive potassium channels leading to vasodilation of coronary vessels. Secondly, they act in a similar manner to nitrates by activating guanylyl cyclase and producing an increase the cGMP levels in vascular smooth muscle cells. This leads to vasodilatation in coronary vessels and also in the venous and arterial systems, leading to a reduction in preload, afterload, and hence myocardial oxygen consumption.
Administration
Oral
Adverse Reactions
Common:
- Headache (usually temporary)
- Flushing
- Nausea and vomiting
- Dizziness
- Rectal bleeding
- Hypotension
- Tachycardia
- Oral ulceration
- Myalgia
- Hypersensitivity
- Specifically nicorandil can cause serious skin, eye and mucosal ulceration which can progress to perforation, haemorrhage, fistula or abscess,
Interactions
Phosphodiesterase type 5 inhibitors such as Sildenafil (treatment of erectile dysfunction) are contraindicated in patients taking potassium channel activators as this combination can cause profound hypotension.
When given alongside NSAIDs an increase the risk of gastrointestinal perforation.
When given alongside NSAIDs an increase the risk of gastrointestinal perforation.
Education
Ensure the patient knows that the treatment is for long term control rather than rapid relief from angina symptoms.
Pharmacokinetics
None
