|
1. |
C.N.S: It lowers the
body temperature by
resetting the thermostat
at a lower level. Heat
production is not
inhibited but heat loss
is augmented by
increasing peripheral
blood flow and sweating.
It has got depressant
action on C.N.S. It is
also probable that
salicylates work by
blocking the pain
centers in the
hypothalamus. It also
acts peripherally as an
anti inflamatory agent
and consequently removes
one of the sources of
stimulation of pain
center, thereby causing
analgesic effect. |
|
2. |
Respiration: it
stimulates the
respiratory centers
causing increased oxygen
consumption and CO2
production. |
|
3. |
Acid base balance and
electrolyte. |
|
4. |
C.V.S |
|
5. |
G.I.T |
|
6. |
On connective tissue
metabolism: The
mechanism of action
involved is the
non-specific effect of
the salicylate to reduce
the increased capillary
permeability by
inflammatory processes. |
|
7. |
Endocrine |
|
8. |
|
Side
effects:
|
a)Gastric
Irritation |
| |
b)Gastric
Intestinal
Bleeding |
| |
c)High
pitched
tinnitus |
| |
d)Vertigo,
Deafness |
| |
e)Hyperthermia |
| |
f)Behavioural
Changes |
| |
g)Respiratory
Alkalosis |
| |
h)Metabolic
Acidosis |
|
| |
|
The main aim in the treatment of
over dose toxicity consists in
gastric lavage and maintenance
of urinary output.
PARA AMINO PHENOL
DERIVATIVE (PARACETAMOL)
These were known as Coal Tar
Antipyretics. Acetanilid was
first introduced in medicine by
Cahn et al (1986) under the name
Antifabrin. Later on Smith
(1953) and Randall (1963)
reviewed the pharmacology and
toxicology of these products.
Pharmacological
action:
Antipyresia:
These drugs also act on the
central nervous system and reset
the thermostat which is set at a
higher level in the febrile
patients. It causes dissipation
of body heat through cutaneous
vasodilation.
Analgesic:
The mechanism of action for the
relief of pain is same as in
salicylates. The type of pain
relieved is that of moderate
intensity such as usually occurs
in headache, dsymmenorhoea and
in many muscles. Joint and
peripheral nerve affection.
Smith (1958) Randall (1963)
found that it raises the
threshold for pain. The
analgesic effect is over in
about 3 to 4 hours.
Other Effects:
Therapeutic dose of these groups
of drugs are benign to the
cardiovascular and respiratory
system. Acid base changes do not
occur. They do not impair renal
or hepatic function if given for
a short time. Neither depression
of the prochrombin level nor
production of haemorrhagical
manifestation is observed.
Acetaminophen appears to have
less over all toxicity and may
be a desired analgesic
antipyretic substitute for
salicylate in patient’s in whom
salicylates are contraindicated
for causes of troublesome side
effects.
Tolerance,
Habituation and Addiction:
Rarely a person may become
habituated to these groups if
taken even for a number of
years. It has been reported that
withdrawal symptoms of
restlessness and excitement may
appear for 3 to 4 days when
medicine is stopped but it is
extremely doubtful that
addiction occurs.
Absorption, Fate
and Excretion:
They are completely absorbed
from the GIT and plasma peak
levels are reached within 1.5 to
2 hours. Detectable levels are
present up-to 5 hours. The drugs
are metabolised by the
microsomal enzyme systems of the
liver and is excreted in the
urine.
Therapeutic use:
Analgesia and Antipyresis.
Toxicology:
Very large doses may cause
haemoglobicema,
sulfhaemoglobinemia and
cyanosis. Anemia may also be
found but it is not due to
depression of bone marrow as
reticulocytes count in
peripheral blood is increased.
This is due to the shortened
life span of RBC. The liver may
be damaged in very large doses,
resulting in jaundice. The
treatment of poisoning is
gastric lavage and according to
the complication.
