My wife's sex drive seems to have disappeared. granted, we do have 4 kids together but we are also only 24. is there a medical solution?

Most likely: She should definitely see her doctor, but it is very likely that she is just tired from being a mom to 4 young children. If your relationship needs any work, then do that work. If there is any way her load can be lightened, see that that happens. Take a vacation (sans kids). Medical factors and treatments can be helpful, but most of the time the solution is not medical.

Usually personal: Interest is sex is a function of biology, alertness, mood and environment. It seems as if you have had four children in a short time span. Is your wife exhausted? Are you helping her raise the kids? Is she healthy otherwise? If there are no medical problems, it might help to surprise her with flowers or a desired gift or praise. Consider a weekend off in a romantic setting.