Chemical formula: C₁₉H₁₈CaN₂O₉ Molecular mass: 458.436 g/mol
Carbasalate calcium is a complex of calcium acetyl salicylic acid and urea. It is a thrombocyte aggregation inhibitor. The antithrombotic effect is due to the irreversible acetylating of the enzyme cyclo-oxygenase in the thrombocyte, through which the formation of the prostaglandin thromboxane A2 is inhibited.
Due to the irreversible nature of the binding, the effect persists for the lifespan of a thrombocyte (7-10 days) and the effect is cumulative after repeated dosing. As a result it is possible to achieve maximum thromboxane A2 inhibition after initially higher starting dose followed by lower maintenance doses to compensate for the creation of new thrombocytes.
After oral administration, acetyl salicylic acid is rapidly absorbed in the proximal part of the small bowel. The maximum plasma concentration is reached after 0.5-2 hours. However, a considerable part of the dose is hydrolysed in the gastric wall during absorption. Simultaneous ingestion of food delays the uptake of acetyl salicylic acid (lower peak plasma concentrations).
The volume of distribution of acetyl salicylic acid is approx. 0.20 l/kg bodyweight. The first conversion product formed from acetyl salicylic acid, anti-inflammatorily effective salicylic acid, is bound to plasma proteins, primarily albumin, to the 90% level. Salicylic acid diffuses slowly to the synovia and the synovial fluid. It penetrates the placenta and passes over into the maternal milk.
Acetyl salicylic acid is primarily converted into salicylic acid by hydrolysis. The half-life of acetyl salicylic acid is short, approx. 15-20 minutes.
Salicylic acid is then converted into glycine acid and glucuronic acid conjugates and traces of gentisic acid. At higher therapeutic doses the conversion capacity of salicylic acid is already exceeded and the pharmacokinetics is non-linear. This leads to a prolongation of the apparent elimination half-life of salicylic acid from a few hours to approximately 24 hours.
Excretion is primarily via the kidneys.
The tubular resorption of salicylic acid is pH-dependent. By alkalising the urine the proportion of unchanged salicylic acid in the excretion increases from approx. 10% to approx. 80%.
Mutagenic and carcinogenic potential.
The acetylsalicylic acid has been assessed in many in vitro and in vivo pre-clinical studies. Taken together the results didn’t reveal any mutagenic effect. Long term studies on rat and mouse didn’t reveal any carcinogenic effect.
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