It is generally possible to take pseudoephedrine with DayQuil, but caution is advised due to potential interactions and overlapping ingredients. DayQuil often contains phenylephrine, which is another decongestant, so taking pseudoephedrine (a nasal decongestant) together could increase the risk of side effects like elevated blood pressure and increased heart rate, since both are stimulants. Also, combining these should be done carefully to avoid excessive stimulation and other potential side effects like insomnia or nervousness. Many sources suggest that there is no direct severe interaction, but because both medications contain decongestants, taking them together may increase the side effects. It's important not to exceed the maximum recommended dosage of either medication and to monitor blood pressure and overall reaction. If there are underlying conditions like hypertension or heart problems, consulting a healthcare provider before combining these medications is highly recommended. Also, a gap of several hours between taking these medications might reduce risks. In summary:

• DayQuil contains phenylephrine, a decongestant.
• Pseudoephedrine is another nasal decongestant.
• Taking both simultaneously can raise blood pressure and heart rate.
• Use caution especially if you have high blood pressure or heart disease.
• Consult a doctor if unsure, and watch for side effects such as rapid heartbeat, dizziness, or insomnia.

This advice applies to healthy adults; those with specific health conditions should seek medical guidance before combining these drugs.