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