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
Talwin Nx Pharmacology, Pharmacokinetics, Studies, Metabolism - Pentazocine and Naloxone
Talwin Nx Pharmacology, Pharmacokinetics, Studies, Metabolism - Pentazocine and Naloxone
CLINICAL PHARMACOLOGY
Pentazocine is a potent
analgesic which when
administered orally in a 50 mg
dose appears equivalent
in analgesic effect
to 60 mg (1 grain) of codeine.
Onset of significant
analgesia usually
occurs between 15 and 30 minutes after oral
administration, and duration
of action is usually
three hours or longer. Onset and duration
of action and the degree
of pain relief are related both to dose
and the severity of pretreatment
pain. Pentazocine weakly antagonizes the analgesic
effects of morphine
and meperidine; in addition, it produces incomplete reversal
of cardiovascular,
respiratory, and behavioral depression
induced by morphine
and meperidine. Pentazocine has about 1/50 the antagonistic activity
of nalorphine. It also has sedative activity.
Pentazocine is well absorbed from the gastro-intestinal tract.
Concentrations in plasma
coincide closely with the onset, duration, and intensity
of analgesia; peak values occur 1 to 3 hours after oral
administration. The half-life in plasma
is 2 to 3 hours.
Pentazocine is metabolized in the liver
and excreted primarily in the urine. Pentazocine passes into the
fetal circulation.
Naloxone when administered orally at 0.5 mg
has no pharmacologic activity.
Naloxone hydrochloride
administered parenterally at the same dose
is an effective antagonist
to pentazocine and
a proof antagonist
to narcotic analgesics.
TALWIN Nx is a potent
analgesic when administered
orally. However, the presence of naloxone in TALWIN Nx will
prevent the effect of
pentazocine if the product
is misused by injection.
Studies in animals indicate that the presence of naloxone does
not affect pentazocine analgesia
when the combination is given orally. If the combination is given
by injection the action
of pentazocine is
neutralized.
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