You should not name your references bibitemn, but use a short but meaningful key, like author + year. There is no real nice way to avoid long \cite{...} calls in your text. There are no packages I know of for this case, because no one uses that naming scheme.
If you really want to do it you could use a for loop for it, e.g. the one provided by pgffor. It allows the use of ... to define ranges. See the pgf manual for the full syntax:
\documentclass{article}
\usepackage{pgffor}
\makeatletter
\newcommand*\rcite[1]{%
\def\@gtempa{}%
\foreach \n in {#1} {%
\edef\@tempa{,bibitem\n}%
\expandafter\g@addto@macro\expandafter\@gtempa
\expandafter{\@tempa}%
}%
\edef\@gtempa{{\expandafter\@gobble\@gtempa}}%
\expandafter\cite\@gtempa
}
\makeatother
\begin{document}
% 3-10
\rcite{3,...,10}
% 2, 5-10
\rcite{2,5,6,...,10}
% 3, 5, 7, 9
\rcite{3,5,...,10}
\end{document}