Most of the Secondary thrombocytopenia are inherited or acquired .
In acquired thrombocytopenia, the patient's history may include the use of one or several offending drugs.
So I would suggest strongly 287.4 and no other codeset is more appropriate than this.
Have a look at this for clarification:
An individual of any age with newly diagnosed thrombocytopenia is more likely to have an acquired disorder rather than an inherited genetic mutation as the underlying etiology. The myriad causes of acquired thrombocytopenia include autoimmune diseases, increased platelet consumption, splenomegaly, marrow suppression (infectious or drug-mediated), and bone marrow failure. Depending on the patient's age of onset, the most common causes of acquired thrombocytopenia will vary, reflecting the prevailing diseases for each age range. In newborns, bone marrow suppression due to infection, neonatal alloimmune thrombocytopenia (NAIT), and passive transfer of antibodies from a mother with immune thrombocytopenic purpura (ITP) are the most likely causes of thrombocytopenia.14 In childhood, ITP and acute viral infection are most common. For adults, the differential diagnosis is quite broad, reflecting the increased diversity and prevalence of chronic illnesses and malignancy.