Antibiotics are only available by prescription.

抗生素只能凭处方购买。

《牛津词典》

SUTENT is available by prescription only.

索坦只能通过医生处方获得。

youdao

I believe they are toxic and should be used only by prescription.

我则认为，CDS有毒，只能按处方使用。

youdao

Two cholesterol-lowering drugs sold only by prescription were in lower doses considered for over-the-counter sale.

FORBES: FDA Rejects Over-The-Counter Cholesterol Drugs

Condoms and sponges, for example, are not deductible since they are available not by prescription but over the counter.

FORBES: Ask TheTaxgirl: Deducting The Cost Of Birth Control

The drug has been produced by the Swiss pharmaceutical company Novartis and is available by prescription for adult dogs.

BBC: News | Health | 'Prozac' for pooches