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Diphenhydramine Hcl

Detailed information about Diphenhydramine Hcl

Official label facts Owner quick guide first Marketing clearly labeled
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Reviewed / Updated / Sources

Reviewed: Not available

Updated: February 12, 2026, 10:44 PM UTC

Sources:

Pet Owner Quick Guide

Start here first for the simple next-step summary.

Used for:

Your vet decides this. Here's what owners typically ask/watch for.

What to watch for:

  • Vomiting (1 reports)
  • Loss of appetite (1 reports)
  • Injection site bruising (1 reports)

When to call the vet:

  • Repeated vomiting or diarrhea.
  • Severe lethargy (hard to wake, very low energy).
  • Collapse or fainting.
  • Trouble breathing.
  • Facial swelling or hives.
  • Blood in vomit or stool.

What to ask your vet today:

  • Is this medicine the right fit for my pet’s current symptoms?
  • Which warning signs mean I should call back right away?
  • How should I handle missed doses or refusal to take the medicine?
Safety & side effects

What to watch:

  • Vomiting
  • Loss of appetite
  • Injection site bruising

Most reported reactions:

  • Vomiting (1 reports)
  • Loss of appetite (1 reports)
  • Injection site bruising (1 reports)

When to call your vet:

  • Repeated vomiting or diarrhea.
  • Severe lethargy (hard to wake, very low energy).
  • Collapse or fainting.
  • Trouble breathing.
Talk to a Vet / Find a Vet Near You Start Symptom Intake

Data freshness: source data appears current.

Latest refresh: Mar 21, 2026, 10:01 a.m.

Data freshness
  • Medication catalog: Source Roxee | Refreshed Feb 12, 2026, 10:44 PM UTC
  • Animal Drug Product Listing Directory (NDC): Source FDA | Refreshed Mar 21, 2026, 10:01 AM UTC
    Package/product NDCs from FDA’s electronic listing directory (XLS).
  • openFDA reaction terms: Source FDA openFDA | Refreshed Feb 9, 2026, 3:14 AM UTC
  • openFDA case summaries: Source FDA openFDA | Refreshed Feb 9, 2026, 3:21 AM UTC
Image coming soon
Diphenhydramine Hcl

Diphenhydramine Hcl

Drug type: Generic ingredient • Generic profile • No FDA branded products linked

Species: Both

Manufacturer: Not available (source)

Quick Facts

Official label facts first, then secondary summaries. Marketing content is separated below.

Species: Both
Manufacturer: Not available

Adverse Reactions

Snapshot first, detailed rows second. This section summarizes signal data and is not a diagnosis.

Tap or hover a reaction to see what it means in plain language.

Tracked signals
32
Reported cases
32
Serious reports
30
Species represented
2
Grouped by Body System
Digestive (5) · Vomiting, Loss of appetite, Diarrhea Skin & allergy (1) · Application site hair loss Behavior (1) · Anxiety Other (25) · Injection site bruising, Immune mediated haemolytic anaemia, Icterus
Most Reported Reactions
Reaction Body system Cases Species Serious cases
Digestive 1 Dog 1
Digestive 1 Cat 1
Other 1 Dog 1
Other 1 Dog 1
Other 1 Dog 1
Other 1 Dog 1
Other 1 Cat 1
Other 1 Cat 1

Species coverage: Cat (17) Dog (15)

View detailed reaction table
Reaction Body system Species Seriousness Frequency Reports
Digestive Dog Serious - 1
Digestive Cat Serious - 1
Other Dog Serious - 1
Other Dog Serious - 1
Other Dog Serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Digestive Dog Serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Other Dog Non-serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Digestive Cat Serious - 1
Digestive Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Skin & allergy Cat Serious - 1
Behavior Dog Non-serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Source metadata:
Veterinary reference (advanced)

Canonical medication sections are above. This legacy block remains available for deeper cross-reference without cluttering the primary workflow.

At a Glance

Quick facts and links to official labeling and safety signals.

Data freshness
  • Medication catalog: Source Roxee | Refreshed Feb 12, 2026, 10:44 PM UTC
  • Animal Drug Product Listing Directory (NDC): Source FDA | Refreshed Mar 21, 2026, 10:01 AM UTC
    Package/product NDCs from FDA’s electronic listing directory (XLS).
  • openFDA reaction terms: Source FDA openFDA | Refreshed Feb 9, 2026, 3:14 AM UTC
  • openFDA case summaries: Source FDA openFDA | Refreshed Feb 9, 2026, 3:21 AM UTC
Official (FDA)
Identity: Generic ingredient • No FDA branded products linked
No official FDA brand rows linked yet for this ingredient.
Case-reported brands (openFDA): MSK
Catalog species: Both
Safety (openFDA)
Top reactions: Dog 8 • Cat 8 • View
Case summaries: 10 (showing 8) • View
openFDA reports are unverified and do not prove causation.
Diagnosis Codes

Diagnosis-code mappings are not available for this medication yet.

Counseling and Monitoring Highlights

Global Pet owner/Vet mode is controlled in the header. This section avoids duplicate in-page persona tabs.

Top reaction signals
Vomiting (1) Loss of appetite (1) Injection site bruising (1) Immune mediated haemolytic anaemia (1) Icterus (1) Hypothermia (1) Hyperglycaemia (1) High pancreatic-specific lipase (1)

Data Sources & Change Log

Every non-trivial field is expected to include provenance and update timestamps.

Official 1 Clinical 0 Manufacturer 0 Marketing 0
Current Field Facts
  • side_effects: Top reported reactions (openFDA): Vomiting, Lethargy (see also Central nervous system depression in 'Neurological'), Facial swelling (see also 'Skin'), Hives (… (Official, 2026-02-12)
Recent Revisions
  • side_effects updated 2026-02-12 22:44 by etl_backfill • Backfilled from existing medication fields

Top Reported Reactions (openFDA)

De-duplicated reaction terms grouped by body system from FDA openFDA reports (not verified; does not prove causation).

Digestive
Vomiting (1) • Dog Loss of appetite (1) • Cat Diarrhea (1) • Dog Bloody diarrhoea (1) • Cat Blood in vomit (1) • Cat

Showing top 5 for Digestive.

Skin & allergy
Application site hair loss (1) • Cat

Showing top 5 for Skin & allergy.

Behavior
Anxiety (1) • Dog

Showing top 5 for Behavior.

Other
Injection site bruising (1) • Dog Immune mediated haemolytic anaemia (1) • Dog Icterus (1) • Dog Hypothermia (1) • Dog Hyperglycaemia (1) • Cat
Show more (20)
High pancreatic-specific lipase (1) • Cat Heart murmur (1) • Dog Fever (1) • Cat Elevated total bilirubin (1) • Cat Dysphoria (1) • Dog Dermatitis (1) • Cat Dehydration (1) • Dog Death by euthanasia (1) • Dog Death (1) • Cat Cough (1) • Dog Corneal ulcer (1) • Cat Constipation (1) • Dog Blepharospasm (1) • Cat Bilirubinuria (1) • Cat Application site irritation (1) • Cat Anaphylaxis (1) • Cat Anaemia NOS (1) • Dog Adipsia (1) • Cat Active urine sediment (1) • Dog Abnormal cytology (1) • Cat

Showing top 5 for Other.

Data source: FDA openFDA Animal & Veterinary adverse event reports.

Adverse Event Case Summaries (openFDA)

These are individual FDA adverse event reports. They are unverified and do not prove the medication caused the reaction.

Dog, Terrier - Yorkshire, Female, 11 year, 2.57 kilogram • Drug: MSK, Unknown • Reactions: Tiredness (lethargy), Not eating, Diarrhea, Constipation, Jaundice… • Outcome: Euthanized

  • Report ID: USA-USFDACVM-2024-US-050996
  • Serious AE: Yes
  • Treated For AE: No
  • Sex: Female
  • Age: 11.00 Year
  • Weight: 2.570 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
Reactions Reported:
Tiredness (lethargy) Not eating Diarrhea Constipation Jaundice Dehydration Tense abdomen Vomiting Hypothermia Heart murmur Death by euthanasia Intentional misuse
Outcomes: Euthanized

Dog, Terrier - Yorkshire, Female, 10 year, 4.6 kilogram • Drug: MSK, Unknown • Reactions: Cough, Anxiety • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2024-US-029316
  • Serious AE: No
  • Treated For AE: Yes
  • Sex: Female
  • Age: 10.00 Year
  • Weight: 4.600 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
Reactions Reported:
Cough Anxiety
Outcomes: Ongoing

Dog, Pit Bull, Female, 6.5 year, 43 kilogram • Drug: MSK, Injection, Intramuscular, Dose: 1 dose per animal, Frequency: 1 per day • Reactions: Death by euthanasia, Lateral recumbency, Injection site bruising, Injection site swelling, Injection site serosanguinous discharge… • Outcome: Euthanized

  • Report ID: USA-USFDACVM-2023-US-014852
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Female
  • Age: 6.50 Year
  • Weight: 43.000 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Intramuscular
  • Form: Injection
  • Dose: 1 dose per animal
  • Frequency: 1 per day
Reactions Reported:
Death by euthanasia Lateral recumbency Injection site bruising Injection site swelling Injection site serosanguinous discharge Unable to rise Dysphoria Swollen limb
Outcomes: Euthanized

Dog, Maltese, Female, 5 year, 4.218 kilogram • Drug: MSK, Solution, Intramuscular • Reactions: Tiredness (lethargy), Other abnormal test result NOS, Anaemia NOS, Immune mediated haemolytic anaemia, Active urine sediment • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2022-US-060159
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Female
  • Age: 5.00 Year
  • Weight: 4.218 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Intramuscular
  • Form: Solution
Reactions Reported:
Tiredness (lethargy) Other abnormal test result NOS Anaemia NOS Immune mediated haemolytic anaemia Active urine sediment
Outcomes: Ongoing

Dog, Crossbred Canine/dog, Male, 10 year, 31.751 kilogram • Drug: MSK, Injection, solution, Intravenous, Dose: 1.75 mL per animal • Reactions: Anaemia NOS, Weight loss, Icterus, Saline slide agglutination test, positive, Immune mediated haemolytic anaemia… • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2022-US-035613
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Male
  • Age: 10.00 Year
  • Weight: 31.751 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Intravenous
  • Form: Injection, solution
  • Dose: 1.75 mL per animal
Reactions Reported:
Anaemia NOS Weight loss Icterus Saline slide agglutination test, positive Immune mediated haemolytic anaemia Thrombocytopenia
Outcomes: Ongoing

Cat, Domestic Shorthair, Female, 19 month, 4.468 kilogram • Drug: MSK, Unassigned, Unknown • Reactions: Vomiting, Fever, Diarrhea • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2021-US-057884
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Female
  • Age: 19.00 Month
  • Weight: 4.468 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
  • Form: Unassigned
Reactions Reported:
Vomiting Fever Diarrhea
Outcomes: Ongoing

Cat, Domestic Shorthair, Male, 3 year • Drug: MSK, Injection, solution, Unknown • Reactions: Anaphylaxis, Bloody diarrhoea, Vomiting, Fever, Tachycardia… • Outcome: Recovered/Normal

  • Report ID: USA-USFDACVM-2021-US-057809
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Male
  • Age: 3.00 Year
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
  • Form: Injection, solution
Reactions Reported:
Anaphylaxis Bloody diarrhoea Vomiting Fever Tachycardia Tachypnoea Tiredness (lethargy) Seizure NOS
Outcomes: Recovered/Normal

Cat, Domestic Shorthair, Female, 13.5 year, 5.67 kilogram • Drug: MSK, Liquid, Unknown • Reactions: Vomiting, Blood in vomit, Weight loss, Loss of appetite, Elevated total bilirubin… • Outcome: Died

  • Report ID: USA-USFDACVM-2021-US-055950
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Female
  • Age: 13.50 Year
  • Weight: 5.670 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
  • Form: Liquid
Reactions Reported:
Vomiting Blood in vomit Weight loss Loss of appetite Elevated total bilirubin Hyperglycaemia Bilirubinuria Adipsia Death High pancreatic-specific lipase
Outcomes: Died

Data source: FDA openFDA Animal & Veterinary adverse event reports.

Overdose Information

No approved overdose-management text is linked yet. If overdose is suspected, contact a veterinarian or emergency clinic immediately.

Storage & Handling

No approved storage guidance is linked yet for this ingredient. Use manufacturer packaging and veterinary guidance for handling/storage.

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