Drug Interaction Report

Potassium Chloride and Diphenhydramine Injection: Interaction Details

Name: Potassium Chloride and Diphenhydramine Injection Interaction
Creator: Dr. Brian Staiger, PharmD, BCPS

A pharmacist-reviewed analysis of the Potassium Chloride and Diphenhydramine Injection interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Diphenhydramine Injection

Banophen Benadryl Calagel Reformulated Jun 2019 Compoz Dermamycin Diphedryl Diphenhist Dormin

Potassium Chloride

K-Tab Klor-Con Pokonza

Medically reviewed by

Dr. Brian Staiger, PharmD, BCPS

Updated Aug 8, 2026

Editorial policy · Data sources

Interaction severity

Contraindicated

These should generally not be used together.

Minor

Moderate

Major

Contraindicated

How we grade severity & evidence

Severity levels

Contraindicated: These should generally not be used together.
Major: Potentially serious — often needs a change or close monitoring.
Moderate: Can be significant — usually manageable with monitoring.
Minor: Usually limited clinical impact.

Evidence grades

Established: Well documented — supported by controlled studies or strong clinical data.
Probable: Good supporting evidence, though not definitively proven.
Suspected: Some evidence suggests this interaction, but it is not well established.
Possible: Limited or conflicting evidence; the interaction may occur.
Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 10 documented Potassium Chloride interactions, 10 are rated contraindicated — including this one.

Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.

Onset

unspecified

Evidence

theoretical

Severity

Contraindicated

What happens

Increased risk of gastrointestinal irritation

Interaction Deep Dive

Concomitant use of a solid oral dosage form of potassium chloride is contraindicated in patients receiving anticholinergic agents that may arrest or delay passage of potassium chloride through the gastrointestinal tract¹.

Why it happens (mechanism)

Delay in potassium chloride passage through the gastrointestinal tract

Common questions

Can I take Potassium Chloride and Diphenhydramine Injection together?

Increased risk of gastrointestinal irritation Always confirm with your pharmacist or prescriber before making any change.

How serious is the Potassium Chloride and Diphenhydramine Injection interaction?

It is rated contraindicated. These should generally not be used together.

How quickly could this interaction happen?

The documented onset is "unspecified". The timing of this interaction is not well characterized.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

From our Q&A

Real reader questions about these medications, each personally answered by our pharmacist:

Comparing Potassium Chloride To Potassium Gluconate

Questions for your pharmacist

Does my dose of Potassium Chloride or Diphenhydramine Injection need adjusting while I take them together?
What symptoms should prompt me to call you or my prescriber right away?
Does the timing of my doses matter for this combination?
Is there a safer alternative to one of these medications for me?

References (1)

Product Information: Potassium chloride oral extended-release capsules, potassium chloride oral extended-release capsules. BluePoint Laboratories (per DailyMed), Columbus, OH, 2019. DailyMed

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Diphenhydramine Injection

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All Diphenhydramine Injection interactions (123) Diphenhydramine Injection drug information

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Potassium Chloride

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All Potassium Chloride interactions (10) Potassium Chloride drug information

Also serious with: Amitriptyline Trospium / Xanomeline Aclidinium Oral Inhalation Atropine Ophthalmic

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About our interaction database: depth, not breadth

HelloPharmacist doesn't license one of the big commercial interaction databases, so what you'll find here is not a complete list of every known drug interaction. Instead, each entry is researched, analyzed, and written up individually — documented from the published literature, reviewed by a pharmacist, and cited so you can check every source yourself.

If a combination isn't listed here, it means we haven't documented it yet — never that it's safe. For screening a full medication list, we recommend pairing this site with a comprehensive tool like the Drugs.com Interaction Checker and, most importantly, a review by your own pharmacist. For a deep, plain-English, fully sourced explanation of a specific documented interaction — that's exactly what we built this for.

This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.