A pharmaceutical composition for use in reducing the level of a transcription product in a cell, comprising: a double-stranded nucleic acid complex comprising a first nucleic acid strand annealed to a second nucleic acid strand, wherein: (a) the first nucleic acid strand (i) comprises nucleotides and nucleotide analogs, and the total number of nucleotides and nucleotide analogs in the first nucleic acid strand is from 12 to 25, (ii) comprises at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H when the first nucleic acid strand is hybridized to the transcription product, (iii) hybridizes to the transcription product and (iv) comprises a 5' wing region of one or more nucleotide analogs located 5' to the at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H and/or a 3' wing region of one or more nucleotide analogs located 3' to the at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H; and (b) the second nucleic acid strand (i) comprises at least 4 consecutive RNA nucleotides, and (ii) further comprises a 5' wing region of one or more phosphorothioated nucleotides or phosphorothioated nucleotide analogs located 5' to the at least 4 consecutive RNA nucleotides and having an effect of suppressing decomposition by enzymes, wherein said nucleotide analogs are bridged nucleotides, and/or a 3' wing region of one or more phosphorothioated nucleotides or phosphorothioated nucleotide analogs located 3' to the at least 4 consecutive RNA nucleotides and having an effect of suppressing decomposition by enzymes, wherein said nucleotide analogs are bridged nucleotides, wherein the at least 4 consecutive RNA nucleotides are cleaved by RNase H when the second nucleic acid strand is annealed with the first nucleic acid strand, and wherein the second nucleic acid strand further comprises a functional moiety having a targeted delivery function. a double-stranded nucleic acid complex comprising a first nucleic acid strand annealed to a second nucleic acid strand, wherein: (a) the first nucleic acid strand (i) comprises nucleotides and nucleotide analogs, and the total number of nucleotides and nucleotide analogs in the first nucleic acid strand is from 12 to 25, (ii) comprises at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H when the first nucleic acid strand is hybridized to the transcription product, (iii) hybridizes to the transcription product and (iv) comprises a 5' wing region of one or more nucleotide analogs located 5' to the at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H and/or a 3' wing region of one or more nucleotide analogs located 3' to the at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H; and (b) the second nucleic acid strand (i) comprises at least 4 consecutive RNA nucleotides, and (ii) further comprises a 5' wing region of one or more phosphorothioated nucleotides or phosphorothioated nucleotide analogs located 5' to the at least 4 consecutive RNA nucleotides and having an effect of suppressing decomposition by enzymes, wherein said nucleotide analogs are bridged nucleotides, and/or a 3' wing region of one or more phosphorothioated nucleotides or phosphorothioated nucleotide analogs located 3' to the at least 4 consecutive RNA nucleotides and having an effect of suppressing decomposition by enzymes, wherein said nucleotide analogs are bridged nucleotides, wherein the at least 4 consecutive RNA nucleotides are cleaved by RNase H when the second nucleic acid strand is annealed with the first nucleic acid strand, and wherein the second nucleic acid strand further comprises a functional moiety having a targeted delivery function. (a) the first nucleic acid strand (i) comprises nucleotides and nucleotide analogs, and the total number of nucleotides and nucleotide analogs in the first nucleic acid strand is from 12 to 25, (ii) comprises at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H when the first nucleic acid strand is hybridized to the transcription product, (iii) hybridizes to the transcription product and (iv) comprises a 5' wing region of one or more nucleotide analogs located 5' to the at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H and/or a 3' wing region of one or more nucleotide analogs located 3' to the at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H; and (b) the second nucleic acid strand (i) comprises at least 4 consecutive RNA nucleotides, and (ii) further comprises a 5' wing region of one or more phosphorothioated nucleotides or phosphorothioated nucleotide analogs located 5' to the at least 4 consecutive RNA nucleotides and having an effect of suppressing decomposition by enzymes, wherein said nucleotide analogs are bridged nucleotides, and/or a 3' wing region of one or more phosphorothioated nucleotides or phosphorothioated nucleotide analogs located 3' to the at least 4 consecutive RNA nucleotides and having an effect of suppressing decomposition by enzymes, wherein said nucleotide analogs are bridged nucleotides, wherein the at least 4 consecutive RNA nucleotides are cleaved by RNase H when the second nucleic acid strand is annealed with the first nucleic acid strand, and wherein the second nucleic acid strand further comprises a functional moiety having a targeted delivery function.