(FDA approved in bold)

• Angina (vasospastic or effort associated)
  
• Essential hypertension
  
• Paroxysmal supraventricular tachycardia, atrial fibrillation/flutter (IV formulation)
  
• Migraine prophylaxis
  
• Cluster headache prophylaxis
  
• Peyronie’s disease, plantar fibromatosis, Dupuytren’s disease (gel)

• Migraine/cluster: Proposed prior mechanisms included inhibition of smooth muscle contraction preventing arterial spasm and hypoxia, prevention of vasoconstriction or platelet aggregation, and alterations of serotonin release and uptake. Prevention of cortical spreading depression may be the mechanism of action for all migraine preventives
  
• Voltage-gated L-calcium channels mediate calcium influx and are important in regulating neurotransmitter and hormone release

• Migraines – may decrease in as little as 2 weeks, but can take up to 3 months on a stable dose to see full effect
  
• Cluster – usually effective in weeks

• Migraine – goal is a 50% or greater reduction in migraine frequency or severity. Consider tapering or stopping if headaches remit for more than 6 months or if considering pregnancy
  
• Cluster – reduction in the severity or frequency of attacks

• Increase to highest tolerated dose
  
• Migraine/cluster: address other issues, such as medication-overuse, other coexisting medical disorders, such as anxiety, and consider changing to another agent or adding a second agent

• Migraine: For some patients with migraine, low-dose polytherapy with 2 or more drugs may be better tolerated and more effective than high-dose monotherapy. May use in combination with AEDs, antidepressants, natural products, and non-medication treatments, such as biofeedback, to improve headache control
  
• Cluster: At the start of the cycle can use a steroid slam and taper. Valproic acid, lithium, topiramate, and methysergide are effective for many cluster patients

• At higher doses, monitor ECG for PR interval