How long would it take for 10 pills of lorazepam 0.5mg to take effect ?

Ativan (lorazepam) onset: Ativan, or lorazepam, typically has onset of action between 20 - 40 minutes. This medication is a benzodiazepine, which may be used to treat acute anxiety. The medication is tolerance inducing & can therefore be habit forming. It is also a respiratory depressant. Be certain to take the med only exactly as prescribed by your doc.