584 PROLONGED ISOLATED THROMBOCYTOSIS IN INFANTS OF POLYDRUG ABUSERS

Nineteen infants of mothers using methadone plus other drugs developed significant thrombocytosis for more than 16 weeks. These prospectively studied newborns had varying degrees of withdrawal during the first week of life; one had seizures. All were formula fed. As part of a study, 10 received paregoric, 3 phenobarbital and 6 no drugs. Complete blood counts were done every 3 to 7 days in hospital and weekly after discharge. Platelet counts in the first week were the same in both study (mean 258,000±18,000/mm3 S.E.M.) and control (255,000±40,000) infants. Maternal platelet counts were all normal. By the second week there was significant thrombocytosis in study (521,000±68,000) versus control (240,000±45,000) infants (p<.001). Thrombocytosis persisted with a further significant increase at 10 weeks of age (745,000±97,000) (p<.05), platelets exceeding 1,000,000 in 4/19. Thrombocytosis was comparable regardless of treatment. All serial blood counts aside from platelets were normal. Marrow hypermegakaryocytosis suggests overproduction as the mechanism. Thrombocytosis appears to be related to postnatal changes associated with withdrawal and not to treatment. Thrombocytosis may be a factor in the pathogenesis of focal infarcts, and subarachnoid plus germinal plate hemorrhages described in some infants of addicted mothers, and thus may relate to potential long term sequelae in survivors.