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Salicylic acid derivatives (salicylates) belong to the group of non-steroidal anti-inflammatory drugs. Chronic poisoning with salicylates is frequent and then a small increase in the dose may lead to a significant increase in their concentration in the blood serum.
Salicylates are well absorbed in the stomach, but the process takes place mainly in the upper part of the small intestine. They are less absorbed from the rectum (administered in the form of suppositories). They penetrate most tissues and body fluids, including the placenta and breast milk, cerebrospinal fluid and synovial fluid. They bind mainly to albumin (50–80%), and the degree of protein binding depends on their concentration in blood serum. Reduction of binding sites due to cirrhosis, hypoalbuminemia, or the presence of other drugs that displace salicylates from protein binding sites, leads to an increase in the free fraction of salicylates and, consequently, to increased toxicity. The maximum concentration occurs within 2 hours of ingestion.
Salicylates readily cross the placental barrier and pass into breast milk. Taking them late in pregnancy may result in the birth of a child with disturbed hemostasis, acid-base balance, increased respiratory rate and hypoglycaemia.
Salicylates enhance oxidation processes, increasing the concentration of CO2, respiratory stimulation and hyperventilation. In higher doses, when the blood concentration reaches 350 mg / l, they stimulate the respiratory center directly, leading to an increase in the respiratory rate and, consequently, to respiratory alkalosis. The body protects itself against alkalosis by increasing the renal excretion of bicarbonate (sodium and potassium are simultaneously lost). The blood pH is lowered and the bicarbonate concentration is reduced. Additionally, as a result of stimulating the metabolism, metabolic products (acetoacetic acid, pyruvic acid, lactic acid) accumulate in the blood. This leads to metabolic acidosis, which occurs at blood salicylate levels of about 500 mg / l, which corresponds to mild intoxication.
In severe poisoning, the sensitivity of the respiratory center to CO is reduced2 and to the palsy of the vasomotor center.
The degree of severity of poisoning depending on the dose taken:
< 150 mg/kg – reakcja grandoksyczna
150–300 mg / kg – mild to moderate intoxication
300–500 mg / kg – severe poisoning
> 500 mg / kg – potentially fatal poisoning
Symptoms of poisoning
Mild poisoning most often affects people who take the drugs chronically and is characterized by symptoms such as: balance disorders, muscle tremors, tinnitus, hearing disorders – hearing loss, increased sweating, nausea, vomiting, headache, disturbance of consciousness, confusion.
The symptoms of severe poisoning include: hyperventilation, high fever (rhabdomyolysis secondary to hyperthermia), sweating, hypoglycaemia, convulsions, visual-auditory hallucinations, agitation, followed by depression of the central nervous system, paralysis of the respiratory center, and cardiovascular shock. Death is usually caused by respiratory failure accompanied by cardiovascular shock. Occasionally, the cause of death may be hyperthermia. The most common death occurs in chronic poisoning, in the elderly (over 70 years of age), whose mean serum salicylate concentration is 700–900 mg / l.
Treatment
It should be conducted in specialized poison centers.