Hello dear. welcome to HealthCareMagic. Thank you for trusting us. I have gone through your queries and understood your concerns. May I know how long have you been in Zyrtec? what medicines do you use for DVT, hypertension, cholesterol, reflux, asthma, and sleep apnea? Firstly, Zyrtec contains Cetirizine HCl, which is a 2nd generation antihistamine that reduces the effects of natural chemical histamine in the body to treat symptoms caused by allergic reaction such as sneezing, itching eyes/nose, hives, watery eyes, or runny nose. Common side effects of Zyrtec include: drowsiness, fatigue, tiredness, dizziness, dry mouth, sore throat or cough, nausea, constipation, or headache. it can also cause back pain, muscle weakness, chest pain, myalgia/muscle discomfort, leg cramps; but the incidences are few. the symptoms you felt above may be caused by the side effect of Zyrtec alone, but it also possibly can be the interactions of the drugs you d taken. it s better if I knew all your medicines so I could look for the interactions among them and their side effects. here some points to be your concerns: 1. Zyrtec may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert. 2. do not take higher or lower dosage without doctor s permission. 3. tell your doctor about all medical conditions and the drugs you take along with zyrtec. they may affect each other which can increase their toxicity. 4. Avoid drinking alcohol while taking Zyrtec, it can increase sedation. I hope these can be useful to clarify your queries. if you have something else to be discussed, feel free to ask me again in HCM. I hope you ll get better soon. Take care. regards, dr. Asti Yuliadha