Proscriped Cefalexin for infected chest and urinary infection. After only 1 dose of 500 mg capsule (taken together with 2 tables of co-codamol) I experienced, nausea, dizziness, headache, tiredness, unable to focus eyes, weakness in arms and legs, tightness of chest and a one time only electric prickly feeling across top of breasts. The medication was in a plain brown bottle with no propriety packaging and no information regarding side-effects. My doctor has advised to stop taking rest of capsules and is proscribing an alternative antibiotic. Until I read other peoples feedback on this drug I was beginning to think I had been poisoned. The effects above lasted for 8 hours.