Drug Comparison
For educational purposes only — a decision-support tool, not a substitute for clinical judgment.
Side-by-side rubric across 96 psychiatric medications. Every rating traces to a verbatim primary-source quote — click any cell to see it.
How to read this tool ▾
Rating scale
– Favorable / lower than class baseline
± Minimal / equivocal
+ Low / uncommon
++ Moderate / common
+++ High / very common
++++ Very high / class-outlier
Frequency vs severity
F = frequency, S = severity. Each gets its own pill colored on the same traffic-light scale: green → blue → yellow → orange → red. Click any cell for incidence percentages and NNH.
Evidence tier
A Network meta-analysis / RCT / FDA label
B Cohort / registry / pooled label data
C Expert review / textbook / case series
Sourcing
Click any cell to see the verbatim source quote and citation. Missing data shows n/a.
Data depth
++ Graded — frequency + severity, primary-source traces
+ FDA label — §6 frequency only (dashed border). Click for sub-types.
Blank — not yet checked (not “absent”)
–±++++++++++ABCF = frequency · S = severity · Dashed border = FDA label only · Click cell for details
1 drug selected — Diphenhydramine(click to collapse)
1/4 selected
Diphenhydramine
Benadryl · Dramamine
First-Generation H1 Antagonist with Anticholinergic Properties
FDA-approved indications
- Allergic reactions and anaphylaxis adjunct (after acute symptoms controlled with epinephrine)
- Motion sickness
- Parkinsonism and drug-induced parkinsonism when oral therapy impossible/contraindicated
- Drug-induced EPS from antipsychotics
Off-label uses
- Insomnia (OTC use — not FDA-approved as prescription hypnotic)
- Acute dystonia rescue (IM 50 mg)
- Motion sickness
MechanismH1 antagonist with strong anticholinergic and CNS-depressant properties
Half-life~2-7 hours (IV/IM data limited)
Decision GuideWhen to pick each / when to consider an alternative
Diphenhydramine
Consider when
- Acute drug-induced dystonia — first-line IM/IV rescue (25–50 mg); onset within minutes alongside benztropine
- EPS prophylaxis with high-risk antipsychotics — reduces EPS incidence (RR 0.61, meta-analysis n=1648) when co-administered
- Parenteral anticholinergic needed in psychiatric emergency — only first-gen H1 antihistamine routinely available IV/IM
- Broadest indication versatility — simultaneously FDA-approved for allergic reactions, EPS/parkinsonism, motion sickness, and OTC sleep
- +1 more
Consider an alternative when
- Elderly patient — highest anticholinergic burden among comparators (AE = 1.0 reference standard); Beers-listed; dementia risk
- Insomnia treatment — weakest evidence base; excluded from Lancet 2022 NMA; tolerance develops within days of continuous use
- Patient on CYP2D6 substrates — dual CYP2D6 substrate and inhibitor; reduces codeine→morphine conversion and tamoxifen activation
- Concurrent anticholinergic medications — additive burden; delirium risk multiplied in polypharmacy settings
- +1 more
| Axis | Diphenhydramine First-Generation Antihistamine |
|---|---|
| CNS | |
Sedation / somnolence | |
Cognitive dulling / anterograde amnesia | |
| Autonomic | |
Anticholinergic burden | |
Urinary retention / hesitancy | |
| Cardiac | |
QTc prolongation | |
| GI | |
Nausea / GI (general) | |
| Discontinuation | |
Withdrawal / discontinuation | |
| Drug-specific / distinctive axes | |
Tolerance (rapid — limits hypnotic utility) only in Diphenhydramine | |