A 35-year-old woman presents to the emergency department with an acute asthma exacerbation. She is speaking in short phrases, respiratory rate is 28 breaths/min, heart rate 110 beats/min, oxygen saturation 93% on room air and PEFR is 45% of predicted. After initial inhaled salbutamol via spacer and oxygen, what systemic corticosteroid regimen is most appropriate according to Australian guidelines?