As it stands, side effects indirectly influence the value of a drug by reducing its cure rating and giving you a penalty to its overall value. Positive/cure effects on the other hand, have a direct effect by adding to the value of a drug first, and then depending if you hit the sweet spot for the strength, giving you a bonus if its actually a good cure.
I think side/negative effects should actually provide a penalty during production too; with the more severe effects being more detrimental to the value of the drug, and remove or reduce the negative effect on the cure rating - which should be more about how well it cures the intended problem, rather than the other effects.
A reason why this could be a good change is that not only can you see easily what the cost of a negative effect is on your product, but it may also influence players to try and work out the bugs in their medicine - at the moment, I might tend to leave in some side effects because the worst that seems to happen is I get a 20% penalty, whereas if, for example, I created a drug that cured headaches and caused headaches at the same time/rate, I would expect them to 100% cancel each other out and make the drug pretty worthless.
Another way might be to have the base value for the effect and use the cure rating combined with the strength to modify that value; so if my drug cures headaches at optimum strength, but caused them in a very small minority of patients, it would have some value after all.
It would be interesting if certain combinations of effects were given specific treatment too; for example, my insomnia cure causing nightmares should be worse than if my migraine cure did the same thing, given that the first are two sleep related effects.
Another interesting mechanic might be upgradable negative effects… that make things worse and provide another thing to think about when designing production.