Hello Your wife is having strong cough from last 8 days in spite of treatment with doxycyclin 100 mg twice in day. Cough present as such . Your wife is also having headache . Doxycycline is a bacteriostatic drug used in susceptible infection, uncomplicated gonorrhea , relapsing fever & louse-borne typhus, prophylaxis of scub typhus . Since your wife is having cough , so there are so many reasons of such symptoms , these include. 1 Allergic bronchitis , usually I prescribe in such cases terbutalin+chlorapheniramine maleat + dextromethorphan syrup 2 TSF twice in a day. I also recommend levofloxacin 750 mg / day ( once in day ) . 2 Since 8 days passed and headache and cough still present , so this may be due to tuberculosis . Get in X RAY chest with blood for C B C & E S R ( if very high 80 mm of 1st hour then consider about some chronic infection like tuberculosis. 3 Asthmatic allergic bronchitis may be the another such cause in such cases . Some bronchodilator will help such as salbutamol tablet . In my opinion consult another physician and get his opinion. Good luck.