Assuming you are of about the same level, there are two major situations where this might occur. My advice varies depending on how he uses the shot.
Situation 1. 'Murray type' Your opponent plays 'normal shots' for most of the rally, but likes to hit a drop shot to finish the rally. In this case the drop shot is being used instead of a put away forehand, and can only be played when the player is already dictating a point. If this is happening consistently, then you are not pressuring your opponent. You need to take charge of the point and bully your opponent with one of the following: pace, spin, variety, depth, all court play or shot placement.
In this case I would try hugging the baseline and pin the opponent back with consistent, deep and spiny, 3/4 pace rallying shots. The court positioning will rob the opponent of time, allows a quick transition into attacking play and leaves less ground to cover for the dropshot. While the described shot will lead to a moderately fast, high ball which bounces half way between the service line and baseline, this shot will neutralise the drop shot and prevent the opponent dictating the rally, unless they also have an effective high flat shot.
Situation 2. 'Santoro type'. This opponent is a trick shot master, who struggles with regular shots. This player can hit incredible touch shots, but struggles hitting topspin shots. These are the players who can hit incredible drop shot winners off of neutral rally shots. In these cases the best play is to use whatever weapons you have to overwhelm them early in the point.
For instance, against this player I would attack the backhand early in the point, switching between very powerful flat forehands and very heavy topspin forehands. Even the ridiculously gifted cannot hit a successful drop shot off of a fast moving ball with a hard to guess spin and trajectory. In this case many of the attempted drop shots will go into the net or sit up on the service line for an easy put away.
Situation 3: Both are true. The opponent can hold their own in deep rallies, and is capable of hitting a ridiculous drop shot off of any shot you hit. In this case you are outclassed in this match up and you will need to develop stronger shots so that you can trouble your opponent.
A poor man's right handed Verdasco (Wilson Prostaff 95s /w SPPP@50lbs)