MRCP2-0951

MRCP2-0951

A 25-year-old man presents to the Dermatology Clinic with severe acne and is feeling quite distressed about it. He has a history of asthma and has been treated with doxycycline in the past. He is currently using a topical retinoid and benzoyl peroxide. You are considering starting him on oral isotretinoin therapy.
What is the most crucial step to take before initiating isotretinoin in this patient?