Let \(R\) be a domain of integrity, \(d\) the differentiation on \(R\) and \(F\) a field of quotients of \(R\). Denote \(\ell\delta\) the logarithmic derivative on \(F\) defined by \(\ell\delta(f)= f^{-1} df\). The author states the problem of describing all irreducible \(p\in R\) such that \(\ell\delta(p)\in R\). He shows that the use of formal power series can bring a complete solution to the problem in some cases.