Tachycardia and tremor in hands. From?

Hello doctors, my sister (25 years old ), visited an ENT specialist for her recurrent cough to which she was prescribed antibiotics (Levoquin 500) and medicines which included Ascoril LS. After taking the medicine course for just one day, she felt severe tachycardia.  She visited a bank, but came back home halfway, complaining of light headedness and feeling like vomiting. Her heart rate went up to 145 bpm. We took her immediately to our nearest hospital and the physician there asked her to stop Levoquin and Ascoril and prescribed her Ciplar 10 and Allegra. Her ECG also showed a bit of irregularities. Her course is over for a few days now, but her heart rate is still around 90-100 and she sometimes experiences tremors in hands as well. Her Thyroid tests came normal as well. What would she be suffering from? Please help.