More effective cough treatment options are needed, yet no new antitussive drugs have been developed in the last half century, according to Dicpinigaitis. With the discovery of TRPV1, however, pharmaceutical companies’ interest in these medications has surged. Numerous potential novel antitussive agents are now being studied, including antagonists to eosinophil, tachykinin receptor, 5-HT receptor, and TRPV1 receptor; agonists to the delta-opioid receptor, NOP receptor, and GABA-B; endogenous cannabinoids, and large conductance Ca+2-activated K+-channel openers.
Dexamethasone and betamethasone are the corticosteroids used for the purpose although the former is recommended over the latter based on its efficacy, safety, wide availability, and low cost  in spite of some counter-logic.  Betamethasone, on the other hand, is preferred over dexamethasone because it is thought to have better prophylaxis of brain softening of premature fetus.  They are used with the intention to help the lungs of a premature fetus develop before the fetus comes out.  They are given when the fetus is expected to be delivered within 24 to 48 hours. Treatment consists of 2 doses of 12 mg of betamethasone given intramuscularly 24 hours apart or 4 doses of 6 mg of dexamethasone given intramuscularly 12 hours apart. Optimal benefit begins 24 hours after initiation of therapy and lasts 7 days.   Antenatal steroids are currently used up to 36 weeks in some parts of the world obstetric practice. 
A meta-analysis of early randomized clinical trials suggested that the benefits of steroids seemed to stop at 34 weeks, 3 and, although one study has shown a maturing of weekly amniotic fluid lung indices when steroids were given between 34 and 37 weeks, 4 a recent randomized trial showed no difference in RDS when steroids were given, vs controls, during this period in gestation. 5 This is in contradiction to definite benefits of steroids that have been well demonstrated through the years of their use before 34 weeks for prevention of RDS. 3,6