He held various ministerial positions in the Dominican government, including minister of finance, interior and police, foreign affairs, and war and navy.

His father, Miguel Lavastida y Aguirre (1790–1830), was a captain of infantry militias during the España Boba, standing out as one of those who supported José Núñez de Cáceres in the ephemeral independence and died being a commissioner during the Haitian regime.

Miguel Antonio's grandfather, Francisco Lavastida y Valladares, died in Caracas in 1812, while his grandmother, María Manuela Aguirre y López del Pulgar (1753–1839), came from a distinguished family.

While serving as substitute judge of the Court of Appeals of Santo Domingo, he was appointed Minister Secretary of State for Finance and Commerce by President Báez in September 1851 and temporarily assumed the Ministry of Justice and Public Instruction between December 1851 and April 1852.

Under the second presidency of Pedro Santana, he established himself as a figure close to this leader and a member of his clique, occupying the post of minister of the interior and police on three occasions between 1853 and 1856, and also taking up again the portfolio of Finance and Commerce, where he was in charge of the Department of Development.

In July 1857, after learning of the uprising in Santiago against the Báez regime, Lavastida and others close to Santana, suspected of being involved in the revolution, sought refuge in the consulates of France and Great Britain.

He was one of the signatories of the National Manifesto of July 27, 1858, which proposed that Santana take charge of the Dominican State, giving the country its previous course and repealing the Constitution of Moca.

This idea was supported by the French and British consuls of Santo Domingo, who considered it a viable solution to ensure the economic survival and security of the country from Haiti.

In his role as improvised general, Lavastida traveled to the Cibao to verify that the pronouncements of the annexation were in order, since it was feared that that region was more prone to unrest.

[7][8] In September 1861, Francisco Serrano commented in a letter that, due to the total confidence that Santana had in Lavastida, the latter had amassed a considerable fortune, in contrast to the public misery, and that it was rumoured that he had obtained it by illicit means.