Your physically fit patient asks for medicines. Should you prescribe them?

Your patient asks you for a prescription of antibiotic drugs because she is travelling abroad and wants to have medicines handy in case she falls ill.

Your patient asks you for a prescription of antibiotic drugs because she is travelling abroad and wants to have medicines handy in case she falls ill. But you refuse to write her one because you conduct a check-up and find her absolutely fit physically. Are you being too rigid here?