(3R,4R,5S)-4-acetylamino-5-amino-3-(1-ethylpropoxy)-1-cyclohexene-1-carboxylic acid ethyl ester

1. 本品為神經胺酶抑制劑，可直接作用到流行性感冒病毒。
2. 神經胺酸(neuraminidase)是流行性感冒病毒的一個重要的表面蛋白質，它促使新形成的病毒從宿主細胞釋出，而且幫助病毒穿過呼吸道黏膜細胞。
3. 抑制病毒神經胺酸��的作用可以阻止新形成的病毒從感染細胞釋出，降低流感病毒的散播。

治療用：
1.成人一天2次，每次1膠囊(75mg)，連續服用五天；CrC1 10∼30mL/ min：降低劑量至每天1膠囊，連續5天。
2.1歲以上兒童的建議劑量：≦15公斤，每次30mg，每天2次；>15-23公斤，每次45mg，每天2次；>23-40公斤，每次60mg，每天2次；>40公斤，每次75mg，每天2次。
3. 愈早服用，效果愈好。為了使本品的療效發揮至最大，病人應在症狀發生後48小時內服用此藥。

Absorption
Readily absorbed from GI tract. C max for oseltamivir is 65.2 ng/mL. C max for metabolite is 348 ng/mL. AUC (0-12h) for oseltamivir is 112 ng•h/mL. AUC (0-12h) for metabolite is 2,719 ng•h/mL.

Distribution
At least 75% of the dose reaches systemic circulation as oseltamivir carboxylate (bioavailability). The Vd is 23 to 26 L (metabolite); 3% is protein bound (metabolite); 42% is protein bound (parent drug).

Metabolism
Converted to active oseltamivir carboxylate by esterases located predominantly in the liver.

Elimination
The t ½ is 6 to 10 h for the metabolite. The t ½ for the parent drug is 1 to 3 h. More than 90% of oseltamivir is metabolized to oseltamivir carboxylate, which is entirely (more than 99%) eliminated by renal excretion. Less than 20% of the oral dose is eliminated through feces.

Special Populations
Children
Children 12 yr of age and younger clear the prodrug and active metabolite faster, resulting in a lower exposure for a given mg/kg dose.