In the United States, you can purchase (which contains pseudoephedrine) up to the federal limits of 3.6 grams per day and 9 grams per 30-day period . Since one Zyrtec-D tablet typically contains 120 mg of pseudoephedrine, this equals roughly 30 tablets in a single day or 75 tablets every 30 days . Quick Purchase Guide CMEA General Information - DEA Diversion Control Division