Mrs Walker is a 57 year old lady who presented with difficulty sleeping 5 weeks ago. A detailed history excluded potential secondary causes. You both agreed that the likely cause was stress at work and poor sleep hygiene including falling asleep with the television on and drinking up to six cups of coffee a day. You gave Mrs Walker some information on sleep hygiene but she has returned today as she feels things are deteriorating. She is completely exhausted, unable to drive and has started to make mistakes at work as a retail manager.
She has followed all the guidance on sleep hygiene previously discussed. She agrees to a referral for Cognitive Behavioural Therapy for Insomnia (CBT-I) but is requesting a short course of medication to give her some respite whilst she is waiting to be seen. Mrs Walker has a history of mild Depression and Atrial Fibrillation for which she takes Warfarin. She does not smoke or drink any alcohol.
Which one of the following medications would be the most suitable for Mrs Walker?