Using density functional theory calculations, we have examined the interaction of interstitials with various arsenic-vacancy complexes and compared these events to interstitial-vacancy (I-V) interactions. We find that the vacancy of Asm V (m=1-4) and Asm V2 (m=2,3) complexes is easily annihilated by I-V recombination, with barriers of 0-0.08 eV and 0.16-0.21 eV, respectively, for the mono- and the di-vacancy associated complexes. The energy gain from the I-V recombination turns out to be significant (>1.3 eV), implying that As would remain more favorably as Asn (or AsmIn) complexes, rather than as AsmVn in the presence of a large amount of excess interstitials. This suggests that interstitials may play an important role in As transient enhanced diffusion and agglomeration, especially at the early stage of postimplantation thermal annealing. We present the reaction paths and bonding mechanisms for the vacancy annihilation of Vn and AsmVn clusters by I-V recombination.