They can generally be used together in smaller than usual doses or in someone tolerant to one or both. But be careful, and start with a significantly lower dose of each than normal, because central nervous system and respiratory depressant effects may be additively or synergistically increased by taking these 2 drugs together. Taking them both together could also possibly increase the risk of other side effects. The drugs do have slightly different effects, but whether or not you would find it "pointless" is a very subjective question. Carisoprodol (Soma)'s effects are: analgesia, anxiolysis, muscle relaxation, sedation, drowsiness, mild euphoria. Gabapentin's effects are: analgesia (particularly for neuropathic pain), possibly some/limited anxiolysis, anticonvulsant, possibly some sedation/drowsiness, possibly limited/mild antidepressant. Also of course different people are affected differently by these drugs. I have never taken them together myself.