FAA guidance
Do not fly while taking it.
Wait
60 hours
after the last dose
Other FAA documents add more.
If used routinely
The examiner should defer
FAA label
DO NOT FLY
Diphenhydramine is on the FAA's Do Not Fly list, which says the wait time after diphenhydramine is 60 hours, and if the pilot uses it routinely, the FAA's table says the examiner should defer.
Track your medicationsCompare FAA documents: diphenhydramineWhat each of the three FAA documents says, in plain wordsOpen
Wait
- the FAA's Do Not Fly table gives the 60 hours, and its general No Fly wait times count from the last dose
- the allergy sheet's table does not say which of its times is diphenhydramine's
- the sheet's alternative is 5 times the half-life or maximal dosing interval after the last dose
Its general No Fly wait times say a pilot should not fly following the last dose of any medication until a time equal to 5 times the medication's maximum pharmacologic half-life has passed, or 5 times its maximum dose interval where the half-life is not known.
The FAA's allergy sheet lists it, taken orally, as conditionally acceptable — it may be used occasionally (one or two times a week) if other certification criteria are met, with the stipulation that the pilot not exercise the privileges of the airman certificate while taking it, and daily use is not acceptable — and says it is the most common medication seen on autopsy in aircraft accidents; its table lists diphenhydramine among the first-generation medicines, prints fewer times than names beside them, and does not say which time is whose; the sheet says an initial observation time is required to mitigate central nervous system risk, either as noted in the table or 5 times the half-life or maximal dosing interval after the last dose.
The FAA's over-the-counter guide gives a wait time of 60 hours for diphenhydramine and lists it as "No Go", among the sedating products to avoid, which it says can cause incapacitation. The guide says to wait at least five dosage intervals after the last dose before flying if the pilot takes any of its No Go medications or has previously had side effects from the medication. The guide notes that the wait times for sedating antihistamines are longer than noted in its Dosage Interval Wait Timetable, due to their longer half-life, and to consult the examiner. All three documents are quoted.
- 60 hours after the last dose: no flying
Show the FAA's words: diphenhydramineThe official FAA wording: six passages, each with its document and dateOpen
DO NOT FLY (DNF) MEDICATIONS
The following medications have aeromedically concerning safety profiles. All medications listed below may cause sedation or drowsiness, impairing cognitive function and seriously degrading pilot performance.
ALLERGY MEDICATIONS (1st GENERATION)
Sedating Antihistamines:
Found in many over-the-counter (OTC) allergy and other types of medications, as a single agent or in any combination product.
Applies to nasal, ophthalmic, AND oral formulations.
diphenhydramine (Benadryl)
chlorpheniramine (Coricidin; ChlorTrimeton)
SEDATIVES/SLEEP AIDS
Diphenhydramine (Benadryl) - Many OTC sleep aids contain diphenhydramine as the active ingredient (see sedating antihistamines above).
The wait time after diphenhydramine is 60 hours (based on maximum pharmacologic half-life)
DO NOT FLY (DNF) MEDICATIONS
AMEs should caution pilots on use and provide additional No Fly wait times where applicable. If applicant is using the following medications routinely, AMEs should DEFER.
GENERAL NO FLY WAIT TIMES
For Aviation safety, pilots should not fly following the last dose of any medications until a period of time has elapsed equal to:
A. 5-times the maximum pharmacologic half-life of the medication (preferred); or
B. 5-times the maximum hour dose interval if pharmacologic half-life information is not available.
Conditionally acceptable medications:
May be used occasionally (1-2 times a week) with the stipulation that the airman not exercise the privileges of airman certificate while taking the medication.
Daily use is NOT acceptable.
Initial observation time: Required to mitigate central nervous system risk, either as noted in the table below or 5x the half-life or maximal dosing interval after the last dose.
CONDITIONALLY ACCEPTABLE (Sedating) Antihistamine Medications
May be used occasionally (1-2 x per week) as a single agent or in any combination product if other certification criteria are met. NOT FOR DAILY USE.
Medication Drug Class Initial observation
Oral: All First-Generation Histamine-H1 receptor antagonist
diphenhydramine (Benadryl)**
doxylamine (Unisom)
brompheniramine
chlorpheniramine (Coricidin; ChlorTrimeton)
clemastine (No brand)
60 hours
60 hours
5 days
5 days
** Diphenhydramine is the most common medication seen on autopsy in aircraft accidents.
4. NO GO Medications:
If you take any of the NO GO medications listed in the OTC Medications Reference Table OR if you have previously had side effects from the medication, wait at least five (5) dosage intervals after the last dose before flying.
Caution: Sedating antihistamine medications have a long half-life so wait time is 60 hours for both diphenhydramine (Benadryl) and doxylamine (Unisom), 5 days for both chlorpheniramine and clemastine.
AVOID
These can cause incapacitation.
NO GO
Sedating products:
brompheniramine (Dimetapp)
cetirizine (Zyrtec)
chlorpheniramine (Chlor- Trimeton)
diphenhydramine (Benadryl)
levocetirizine Xyzal)
dimenhydrinate (Dramamine)
meclizine (Antivert)
Sedating antihistamines can cause drowsiness and impaired thinking and judgement.
NOTE: Sedating antihistamines are commonly found in autopsy after aircraft accidents. The wait times for these medications are longer than noted in the “Dosage Interval Wait Timetable” due to their longer half-life. Consult your AME.