What the FDA labels say about taking them together
Guanfacine and phenylephrine
Phenylephrine's FDA label of August 19, 2026 names guanfacine in its drug interactions section; the guanfacine label PlainMeds reads does not name phenylephrine. The phenylephrine label: “… ACE inhibitors Centrally acting sympatholytic agents, such as reserpine, guanfacine”
Check it at the source: the guanfacine FDA label on DailyMed (effective June 23, 2025, Takeda Pharmaceuticals America, Inc.); the phenylephrine FDA label on DailyMed (effective August 19, 2026, Hikma Pharmaceuticals USA Inc.).
What does the guanfacine label say about phenylephrine?
Guanfacine's label (effective June 23, 2025) does not name phenylephrine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Intuniv), Takeda Pharmaceuticals America, Inc., effective June 23, 2025 (SPL set b972af81-3a37-40be-9fe1-3ddf59852528), via openFDA; the full label on DailyMed
What does the phenylephrine label say about guanfacine?
Phenylephrine label, drug interactionsThe pressor effect of phenylephrine hydrochloride is increased in patients receiving: Monoamine oxidase inhibitors (MAOI), such as selegiline. β-adrenergic blockers α-2 adrenergic agonists, such as clonidine Steroids Tricyclic antidepressants Norepinephrine transport inhibitors, such as atomoxetine Ergot alkaloids, such as methylergonovine maleate Centrally-acting sympatholytic agents, such as guanfacine or reserpine Atropine sulfate
Biorphen label (Dr. Reddy's Laboratories Inc., March 31, 2026), drug interactionsInteractions that Antagonize the Pressor Effect The increasing blood pressure effect of BIORPHEN is decreased in patients receiving: α-adrenergic antagonists Phosphodiesterase Type 5 inhibitors Mixed α- and β-receptor antagonists Calcium channel blockers, such as nifedipine Benzodiazepines ACE inhibitors Centrally acting sympatholytic agents, such as reserpine, guanfacine
Source: FDA drug label (Biorphen, NDA212909), Dr. Reddy's Laboratories Inc., effective March 31, 2026 (SPL set 2f715e4e-b269-b935-d2c9-003cb29770be), via openFDA
Source: FDA drug label (Phenylephrine Hydrochloride), Hikma Pharmaceuticals USA Inc., effective August 19, 2026 (SPL set e1a7ab4b-0afe-4463-a039-5be0323cf2f7), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Guanfacine | Phenylephrine | |
|---|---|---|
| Labeled for | ADHD, High blood pressure | Cough and cold, Allergies |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.147 per tablet 1 mg tablet | $5.24 per mL 10% eye drop |
| Shortage now | A presentation being discontinued | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once