A 32-year-old took Benadryl, Zyrtec, Codeine, Cyclobenzaprine, and Linzess – now feeling shaky and has blurred vision.

1. Possible Drug Interactions and Side Effects:

Diphenhydramine + Cyclobenzaprine + Codeine - These three are all central nervous system (CNS) depressants that have anticholinergic properties, so together they will enhance sedation, blurred vision, dry mouth, confusion, and tremors.

Cetirizine (Zyrtec): This is a second-generation antihistamine; it may be less sedating, but is likely also to increase CNS depression when added to the above combination.

Cyclobenzaprine - will cause sedation, dry mouth, blurred vision, and tremors; since the patient is taking other CNS depressants, the effects may be bigger.

Linzess - works locally in the gut; would not be expected to add to the CNS symptoms

2. Assessment:

The combination does not exceed toxic doses, but the symptoms seem to likely arise from the additive sedative and anticholinergic effects of a combination of Benadryl + Cyclobenzaprine + Codeine.

Blurred vision and shakiness are issues that will not go away.

3. Recommendations:

Immediate:

Stop taking any other sedating medications until a physician clears this up.

Start giving oral fluids, a small light snack

Ensure a safe environment (sitting or lying down to avoid falling).

Monitoring:

Watch for progression of sedation, level of confusion, or walking difficulty, or worsening vision.

Watch for signs of anticholinergic toxicity (flushed skin, dry mouth, urinary retention, and hallucinations).

Medical Advice:

Contact the Poison Center or a pharmacist to review drug interactions.

Come into the emergency department if the symptoms progress, or do not improve over the next few hours, or if any other new symptoms develop.

4. Conclusion:

The doses of medications taken are less than a toxic dose; however, they will increase the potential for CNS and anticholinergic side effects. If symptoms do not improve or worsen, a hospital medical assessment is warranted.