As I have already submitted a paper for on-site therapeutic drug monitoring of aminoglycosides in whole blood, it is included an ethical approval for collecting blood samples
Any study involves patients must has an ethical approval from Ministry of Health (Clinical Research Center) and from the ethical committee of university or institute which the researcher work or study in it.
The quesstion s not very clear to me. If you are asking about a retrospective chart or adverse reaction/safety review that depends. In any case, it is wise to consult with an ethics committee, as many journals will not publish without assurance that ethics clearance had been obtained. There is no uniform approach. It all depends on the Journal where this will be published and the country where you live and what is customary to do there. As with all ethical questions it is case by case and enough details are needed for a black and white yes or no answer