Not terribly uncommon, it is from the D part standing for
pseudoephedrine. It is stimulatory for the CNS which cause restlessness, tremors, heart beating out of your chest, increased blood pressure, etc. SOme people are more sensitive to it than others. If it is bothersome then maybe take a PE product which is phenylephrine and lower grade or less potent decongestant. This is why "D" products should not be take by people with uncontrolled high blood pressure.
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---I answer questions to the best of my ability, but with always limited knowledge of the patient's situation and obviously I can not see your chart or full medical history my advice is limited and should also be confirmed with your own doctor/pharmacist/etc. and I do not promote following my advice without proper approval from your doctor either--
Dr. B