Sedation can wear off anywhere from one to six hours, depending on the type of drug used. Some medications are reported to retain their effects for more than eight hours.
Nitrous or laughing gas, for example, can show its effects rapidly, within one to two minutes. However, once the mask is removed, the effects disappear almost right away. As for IV sedation, it typically takes effect within 15 to 30 minutes, depending on the person and the potency of the drug. Once removed, the patient can wake up in about 20 minutes. Recovery from the sedative effects can take six hours.