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
Darvon Pharmacology, Pharmacokinetics, Studies, Metabolism - Propoxyphene, Aspirin, and Caffeine
Darvon Pharmacology, Pharmacokinetics, Studies, Metabolism - Propoxyphene, Aspirin, and Caffeine
CLINICAL PHARMACOLOGY
Propoxyphene is a centrally acting narcotic
analgesic agent. Equimolar
doses of propoxyphene hydrochloride
or napsylate provide similar plasma concentrations. Following administration
of 65, 130 or 195 mg of propoxyphene
hydrochloride, the bioavailability
of propoxyphene is equivalent
to that of 100, 200, or 300 mg
respectively of propoxyphene napsylate. Peak plasma concentrations
of propoxyphene are reached in two to two and one-half hours. After
a 65 mg oral
dose of propoxyphene hydrochloride
peak plasma levels of
0.05 to 0.1 mcg/ml are achieved.
Repeated doses of propoxyphene at 6-hour intervals lead
to increasing plasma concentrations, with a plateau
after the ninth dose at
48 hours.
Propoxyphene is metabolized in the liver
to yield norpropoxyphene. Propoxyphene has a half-life
of 6 to 12 hours whereas that of norpropoxyphene is 30 to 36 hours.
Norpropoxyphene has substantially less central-nevous-system-depressant
effect than propoxyphene but a greater local
anesthetic effect,
which is similar to that of amitriptyline and antiarrhythmic
agents, such as lidocaine
and quinidine.
In animal studies in
which propoxyphene and norpropoxyphene were continuously infused
in large amounts, intracardiac
conduction time
(P-R and QRS intervals) was prolonged. Any intracardiac
conduction delay
attributable to high concentrations of norpropoxyphene may be of
relatively long duration.
Actions
Propoxyphene is a mild narcotic
analgesic structurally
related to methadone. The potency
of propoxyphene hydrochloride
is from two-thirds to equal that of codeine.
The combination of propoxyphene with a mixture
of aspirin and caffeine
produces greater analgesia
than that produced by either propoxyphene, aspirin, and caffeine
administered alone.
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