tokens: Seventy - five human immunodeficiency virus ( HIV ) - infected patients with CD4 + cell counts < 500 / mm3 were randomized to receive either ZDV ( 500 mg daily ) alone ( group I , n = 38 ) or in combination with folinic acid ( 15 mg daily ) and intramascular vitamin B12 ( 1000 micrograms monthly ) ( group II , n = 37 ) .