woman pouring medication from bottle to cup next to heart with BP Monitor


There is no interaction between losartan (brand name Cozaar) and DayQuil Severe, which contains four active ingredients:

They are considered to be safe to take together.

Phenylephrine And Blood Pressure

The only potential concern taking losartan with DayQuil Severe is that the DayQuil product contains phenylephrine, a nasal decongestant.

Although not as potent when taken by mouth as pseudoephedrine, it has been reported to cause temporary increases in blood pressure, especially in children.

One case study, published in the European Journal of Pediatrics, discussed a 5-year old child whose blood pressure increased from 109/66 mmHg to 135/80 mmHg after taking oral phenylephrine three times daily for 4 days. The blood pressure returned to normal after phenylephrine was discontinued and the authors of the study noted that no alternative causes of the increased blood pressure could be found.

This increase in blood pressure after phenylephrine administration has been noted in a few other case studies. Overall, however, notable changes in blood pressure after taking phenylephrine seem to be pretty uncommon or insignificant for most people.

One of the most extensive review studies on phenylephrine, published in the Annals of Pharmacotherapy, reported at recommended doses, it has no appreciable effect on blood pressure. While the focus of the study was to evaluate the overall effectiveness of phenylephrine as a decongestant, it did discuss side effects and stated:

"Phenylephrine showed no consistent effect on heart rate or blood pressure for doses of 25 mg or less."

Final Words

All in all, as long as your blood pressure is well controlled on losartan, it should be safe to take with the phenylephrine contained in DayQuil Severe. Nevertheless, as with any over-the-counter product, be sure to discuss its use with your doctor prior to use to make sure it is safe with your medical conditions and other medication you may be taking.

Answer Summary

There is no known interaction between losartan (Cozaar) and DayQuil Severe. Some studies show that the phenylephrine in DayQuil Severe can cause small, temporary increases in blood pressure but any change is often insignificant.
  • Elsevier ClinicalKey: Phenylephrine Monograph (Accessed 2/24/19)
  • Elsevier ClinicalKey: Losartan Monograph (Accessed 2/24/19)
  • Clinical Inquiry: Do oral decongestants have a clinically significant effect on BP in patients with hypertension? PubMed
  • Efficacy and safety of oral phenylephrine: systematic review and meta-analysis. PubMed
  • Are oral decongestants safe in hypertension? An evaluation of the evidence and a framework for assessing clinical trials. PubMed
  • Cold medication containing oral phenylephrine as a cause of hypertension in children. PubMed