My Dad Is Currently Being Treated For Cellulitis In His

My Dad is currently being treated for cellulitis in his foot and is being treated with oral antibiotics. He has early onset vascular dementia and since his cellulitis developed he has been very sleepy and his memory appears to have deteriorated. He is otherwise well in himself and does not have a temperature . Is it normal for him to feel and be so sleepy? His cellulitis is improving daily.