However, if one tricyclic is not helpful, other members of the family should be tried, i.e., desipramine, imipramine, doxepin, amitriptyline. Unfortunately, besides taking weeks to work, tricyclics work unevenly, so that good days and bad days are common. The leading reasons for failure are an inadequate dosage over too short a period of time or an intolerance of side effects. If the patient fails to improve after 3 months of therapy at a daily dosage of 100 to 150 mg, another agent should be tried. Tricyclics are contraindicated in patients with urinary retention and glaucoma.
Caution is advised in patients with cardiac arrhythmias.
They also are sun sensitizers. When the tricyclics are not helpful, anticonvulsants may be tried instead. Although carbamazepine and dilantin originally were used for VDY, the drug levels and monitoring of blood chemistries that are required make them less attractive alternatives. Gabapentin is preferred, starting at 100 mg at bedtime and increasing by 100 mg every 2 days. If the drug is tolerated without difficult side effects, doses up to 4 or 4.5 g may be used if necessary.