Does using gripe water along with dentinox colic drops for babies have side effects? Sedative? Harmful?

Usually ok. Doctors usually don't give babies any medications, even over-the-counter items, unless there's good benefit. A mom can bring the items to the doctor to check the ingredients, but a little bit of a trusted brand of gas drops and gripe water drops are ok to try. They may or may not help any colicky symptoms. If they don't seem to help, then they shouldn't be used.
Dentinox/Gripe water. Gripe water is made of terpeneless dill seed oil and sodium hydrogen carbonate used for symptomatic relief of distress associated with gases in infants up to one year. Dentinox is dimethicone used for relief of gas and griping pains in infants. There are no known drug interactions between gripe water and dentinox. However, it is better to consult the pediatrician before making this combination.