A1,
A2,
B,
C1,
C2,
D,
E,
F,
G-H,
I-K,
L,
M,
N,
O,
P1,
P2,
Q-R,
S,
T,
U-V,
W-Z
Minipress Side Effects, and Drug Interactions - Prazosin HCl
Minipress Side Effects, and Drug Interactions - Prazosin HCl
SIDE EFFECTS
Clinical trials were conducted on more than 900 patients. During these
trials and subsequent marketing experience, the most frequent reactions
associated with prazosin HCl therapy are: dizziness 10.3%, headache 7.8%,
drowsiness 7.6%, lack of energy 6.9%, weakness 6.5%, palpitations 5.3%,
and nausea 4.9%. In most instances side effects have disappeared with
continued therapy or have been tolerated with no decrease in dose of drug.
Less frequent adverse reactions which are reported to occur in 1-4% of
patients are:
Gastrointestinal: vomiting, diarrhea, constipation.
Cardiovascular: edema, orthostatic hypotension, dyspnea,
syncope.
Central Nervous System: vertigo, depression, nervousness.
Dermatologic: rash.
Genitourinary: urinary frequency.
EENT: blurred vision, reddened sclera, epistaxis, dry mouth,
nasal congestion.
In addition, fewer than 1% of patients have reported the following (in
some instances, exact causal relationships have not been established):
Gastrointestinal: abdominal discomfort and/or pain, liver
function abnormalities, pancreatitis.
Cardiovascular: tachycardia.
Central Nervous System: paresthesia; hallucinations.
Dermatologic: pruritus, alopecia, lichen planus.
Genitourinary: incontinence, impotence, priapism.
EENT: tinnitus.
Other: diaphoresis, fever, positive ANA titer, arthralgia.
Single reports of pigmentary mottling and serous retinopathy, and a few
reports of cataract development or disappearance have been reported. In
these instances, the exact causal relationship has not been established
because the baseline observations were frequently inadequate.
In more specific slit-lamp and funduscopic studies, which included adequate
baseline examinations, no drug-related abnormal ophthalmological findings
have been reported. Literature reports exist associating prazosin therapy
with a worsening of pre-existing narcolepsy. A causal relationship is
uncertain in these cases.
DRUG INTERACTIONS
Prazosin has been administered without any adverse drug interaction in
limited clinical experience to date with the following: (1) cardiac glycosides
- digitalis and digoxin; (2) hypoglycemics - insulin, chlorpropamide,
phenformin, tolazamide, and tolbutamide; (3) tranquilizers and sedatives
- chlordiazepoxide, diazepam, and phenobarbital; (4) antigout - allopurinol,
colchicine, and probenecid; (5) antiarrhythmics - procainamide, propranolol
(see WARNINGS), and quinidine;
and (6) analgesics, antipyretics and anti-inflammatories - propoxyphene,
aspirin, indomethacin, and phenylbutazone.
Addition of a diuretic or other antihypertensive agent to prazosin HCl
has been shown to cause an additive hypotensive effect. This effect can
be minimized by reducing the prazosin dose to 1 to 2mg three times a day,
by introducing additional antihypertensive drugs cautiously and then by
retitrating prazosin based on clinical response.
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