DOSAGE & ADMINISTRATION
The dose of verapamil hydrochloride must be individualized by
titration. The usefulness and safety of dosages exceeding 480 mg/day have not
been established; therefore, this daily dosage should not be exceeded. Since the
half-life of verapamil increases during chronic dosing, maximum response may be
delayed.
Angina
Clinical trials show that the usual dose is 80 mg to 120 mg three
times a day. However, 40 mg three times a day may be warranted in patients who
may have an increased response to verapamil (e.g., decreased hepatic function,
elderly, etc.). Upward titration should be based on therapeutic efficacy and
safety evaluated approximately eight hours after dosing. Dosage may be increased
at daily (e.g., patients with unstable angina) or weekly intervals until optimum
clinical response is obtained.
Arrhythmias
The dosage in digitalized patients with chronic atrial
fibrillation (see PRECAUTIONS) ranges from
240 to 320 mg/day in divided (t.i.d. or q.i.d.) doses. The dosage for
prophylaxis of PSVT (non-digitalized patients) ranges from 240 to 480 mg/day in
divided (t.i.d. or q.i.d.) doses. In general, maximum effects for any given
dosage will be apparent during the first 48 hours of therapy.
Essential Hypertension
Dose should be individualized by titration. The usual initial
monotherapy dose in clinical trials was 80 mg three times a day (240 mg/day).
Daily dosages of 360 and 480 mg have been used but there is no evidence that
dosages beyond 360 mg provided added effect. Consideration should be given to
beginning titration at 40 mg three times per day in patients who might respond
to lower doses, such as the elderly or people of small stature. The
antihypertensive effects of verapamil are evident within the first week of
therapy. Upward titration should be based on therapeutic efficacy, assessed at
the end of the dosing interval.
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