tetracycline(out) + H(+)(in) => tetracycline(in) + H(+)(out)
tetracycline(out) + h(+)(in) => tetracycline(in) + h(+)(out)
tetracycline(out) + H(+)(in) => tetracycline(in) + H(+)(out)
tetracycline(out) + h(+)(in) => tetracycline(in) + h(+)(out)