  Planets are formed from collisional growth of small bodies in a
protoplanetary disk. Bodies much larger than approximately $1$\,m are mainly
controlled by the gravity of the host star and experience weak gas drag; their
orbits are mainly expressed by orbital elements: semimajor axes $a$,
eccentricities $e$, and inclinations $i$, which are modulated by gas drag. In a
previous study, $\dot a$, $\dot e$, and $\dot i$ were analytically derived for
$e \ll 1$ and $i \ll H/a$, where $H$ is the scale height of the disk. Their
formulae are valid in the early stage of planet formation. However, once
massive planets are formed, $e$ and $i$ increase greatly. Indeed, some small
bodies in the solar system have very large $e$ and $i$. Therefore, in this
paper, I analytically derive formulae for $\dot a$, $\dot e$, and $\dot i$ for
$1-e^2 \ll 1$ and $i \ll H/a$ and for $i \gg H/a$. The formulae combined from
these limited equations will represent the results of orbital integration
unless $e \geq 1$ or $i > \pi - H/a$. Since the derived formulae are applicable
for bodies not only in a protoplanetary disk but also in a circumplanetary
disk, I discuss the possibility of the capture of satellites in a
circumplanetary disk using the formulae.
