アラニジピン

The binding ratio of plasma proteins of aranidipine varies from 84-95%. This ratio of the drug is similar to the unchanged form and for the M-1 metabolite. Most of the binding happens towards serum albumin and a lower amount corresponds to the alpha1-acid glycoprotein.

Pre-clinical studies with aranidipine and its two metabolites have shown production of increases in femoral blood flow. It has been shown to present potent and long-lasting vasodilating actions. Aranidipine and its metabolites are shown to inhibit calcium-induced contraction in isolated rabbit arteries. Studies have shown that aranidipine is more potent to reduce blood pressure than other dihydropyridines. Aranidipine produce changes in renal blood flow, this effect may be explained by its effect on alpha-2-adrenoreceptor-mediated vasoconstriction.

The high potential of aranidipine is thought to be related to the additional calcium antagonistic activity of its metabolite. The mechanism is thought to be related to the capacity of aranidipine and its metabolites to vasodilate afferent and efferent arterioles. this action is performed through the inhibition of voltage-dependent calcium channels. The typical mechanism of action of aranidipine, as all dihydropyridines, is based on the inhibition of L-type calcium channels, decreasing calcium concentration and inducing smooth muscle relaxation. It is a selective alpha2-adrenoreceptor antagonist which inhibits vasoconstrictive responses.

After administration, aranidipine is rapidly absorbed from the gastrointestinal tract. After absorption, the AUC and Cmax increased linearly in a dose-dependent manner, the Cmax was attained in approximate 3.8-4.8 hours for aranidipine and 4.8-6 hours for the metabolite M-1. The bioavailability of aranidipine in rat, dog, and monkey was about 48%, 41% and 3% respectively.

Unchanged aranidipine is found in plasma but not in the urine after 1 hour of administration. Just a small amount of drug was found in the bile. These results indicate that the excretion profile of aranidipine is mainly driven by metabolism and not by excretion. When including the metabolites, 52-56% of the original dose is disposed in the urine, 34-45% in feces and 3-4% in expired air. The excretion in the bile was 59% of the administered dose and 63% of this portion is reabsorbed.