Take ten drops every four hours.

每隔四小时喝十滴。

《新英汉大辞典》

Take one tablet every four hours.

隔四小时服一片。

youdao

Please take these pills every four hours.

请每隔四小时吃一次这些药片。

youdao

A new study found better results in four-year-olds who go to bed around the same time every night and sleep at least eleven hours.

VOA: special.2010.06.09

And for the space of four hours every night, I feel no boredom.

每晚四小时的学习，我一点也不觉得无聊。

耶鲁公开课 - 政治哲学导论课程节选

But,the turbo-prof will be somebody who is assigned to Reims, and who takes the train there every day, or to Tours; but to Lyon also since this is only two hours, this is four-hundred kilometers.

不过涡轮教授被派到兰斯教书,他每天都要坐火车往返,抑或是去图尔斯,从这里去里昂要用两小时,这有四百公里

耶鲁公开课 - 1871年后的法国课程节选

Should you eat a meal every four hours or just make sure to eat several small meals throughout the day?

CNN: Information overload: Finding fitness that works for you

Dr Katherine Astbury told the coroner that Mrs Halappanavar's vital signs were not checked every four hours after her membranes ruptured.

BBC: Savita Halappanavar

One aimed to insure that nurses observe patients for pain at least once every four hours and provide timely pain medication.

NEWYORKER: The Checklist