The dissertation consists in the development of a model to evaluate the welfare effects of monetary policy in an economy where the government faces some restriction to debt financing. The government, in the model, is able to finance its expenditures by issuing public debt or levying two kinds of taxation: lump sum and distortionary taxes. The hypothesis adopted here is that the government cannot set a constant rate of distortionary taxation over time, and let either the debt stock or the lump sum taxation to adjust in response to shocks. Instead, the government will be forced to adjust the current distortionary taxation in response to variations of the debt service. The conclusion is that the optimal monetary policy rule that results from this model is quite different from the optimal rule in the absence of restrictions to debt financing.