Tripelennamine
Tripelennamine hydrochloride
Also known as: Re-Covr · Azaron · Etono · Fenistil · PBZ · Pelamine · Pyribenzamine · Vaginex · Tripelennaminium chloride
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| General antihistamine | 1 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
| General antihistamine | 1 mg/kg IM | IM | — | — | 🌎 NA |
- General antihistamine: Oral dosage forms may no longer be obtainable
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| General antihistamine | 1 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
| General antihistamine | 1 mg/kg IM | IM | — | — | 🌎 NA |
- General antihistamine: Oral dosage forms may no longer be obtainable
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| General antihistamine | 1.1 mg/kg (2.5 mL per 100 lbs body weight) IM q6-12h as needed | IM | q6-12h | as needed | 🌎 NA |
| General antihistamine | 1 mg/kg IM | IM | — | — | 🌎 NA |
- General antihistamine: Do NOT give IV. ARCI UCGFS Class 3 Drug.
- General antihistamine: Do NOT give IV. ARCI UCGFS Class 3 Drug.
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| General antihistamine | 1.1 mg/kg (2.5 mL per 100 lbs body weight) IV (for more immediate effect) or IM q6-12h as needed | IV/IM | q6-12h | as needed | 🌎 NA |
| Downer Cow Syndrome (Adjunctive treatment) | 0.5 mg/kg slow IV in conjunction with parenteral mineral treatment | IV | — | — | 🌎 NA |
| General antihistamine | 1 mg/kg IV or IM | IV/IM | — | — | 🌎 NA |
- Downer Cow Syndrome (Adjunctive treatment): Used as a CNS stimulant
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| General antihistamine | 1 mg/kg IV or IM | IV/IM | — | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Tripelennamine is a first-generation, ethylenediamine-derivative antihistamine used primarily in large animal veterinary medicine. It is utilized to mitigate histamine-mediated allergic reactions and anaphylaxis.
Interestingly, it is also employed off-label as a CNS stimulant in "Downer cow" syndrome when administered via slow IV. Because it is a first-generation antihistamine, it readily crosses the blood-brain barrier, which can cause significant central nervous system (CNS) effects ranging from sedation to paradoxical excitation (especially in horses).
Clinical Pearl: While highly effective for acute allergic reactions, its use has declined in small animal medicine due to the availability of newer, less sedating antihistamines and the discontinuation of many oral tripelennamine formulations.
Mechanism of action
Tripelennamine acts as a competitive antagonist at the H1-receptor.
- Histamine Release → Histamine binds to H1 receptors on smooth muscle, endothelium, and the CNS.
- Tripelennamine → Competes for these receptor sites → Prevents histamine-induced bronchoconstriction, vasodilation, and increased capillary permeability.
Note: Antihistamines do not inactivate histamine or prevent its degranulation/release from mast cells; they only block its downstream effects. Compared to other antihistamines, tripelennamine has moderate sedative activity and minimal anticholinergic activity.
Safety & warnings
Contraindications
- Intravenous (IV) administration in horses is strictly contraindicated due to severe CNS stimulation
Adverse effects
- CNS stimulation (hyperexcitability, nervousness, muscle tremors) - especially in horses given IV
- CNS depression / Sedation
- Ataxia / Incoordination
- Gastrointestinal disturbances
Precautions
WARNING: Do NOT administer intravenously (IV) to horses due to the risk of severe CNS stimulation, hyperexcitability, and muscle tremors.
- Administration: It is recommended to warm the injectable solution to near body temperature before injecting. Give IM injections deep into large muscle areas.
- Allergy Testing: Antihistamines can decrease the wheal and flare response to antigen skin testing. Discontinue at least 4 days prior to intradermal testing to avoid false-negative results.
- Food Animal Residues: In cattle, meat withdrawal is 4 days following the last treatment. Milk must not be used for food for 24 hours (2 milkings) after treatment.
Drug interactions
Increased sedation and CNS depression
May partially counteract the anticoagulation effects
May partially counteract the anticoagulation effects
Monitoring
- Clinical efficacy (resolution of allergic signs)
- Adverse effects (CNS stimulation, sedation, ataxia)
Pharmacokinetics
Half-life
Distribution
Volumes of distribution steady-state approximately 1.5-3 L/kg (in horses and camels). Protein binding is approximately 80%.
Elimination
Total body clearance is approximately 1 L/hour/kg (in horses and camels).
Overdose
Overdosage of tripelennamine can cause CNS excitation, seizures, and ataxia.
- Treatment: Treat symptomatically and supportively if clinical signs are severe.
- Seizure Management: Phenytoin (IV) is recommended in the treatment of seizures caused by antihistamine overdose in humans. Barbiturates and diazepam are generally avoided as they may exacerbate post-excitatory CNS depression.
Available products
Formulations
- Injection: 20 mg/mL
- Oral dosage forms may no longer be obtainable
Veterinary
- Tripelennamine HCl for Injection: 20 mg/mL in 20 mL, 100 mL, and 250 mL vials (Re-Covr, generic)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store the injection at room temperature and protect from light; avoid freezing or excessive heat. The white crystalline powder will slowly darken upon exposure to light.
Client information
- Purpose: This medication is an antihistamine used to treat allergic reactions, hives, and sometimes utilized as a stimulant in specific cattle conditions (like "Downer cow").
- Administration: It is usually given by injection by your veterinarian. If oral forms are prescribed, give exactly as directed.
- Side Effects: Watch for drowsiness, lack of coordination, or conversely, extreme nervousness and muscle tremors.
- Important Warning: Do not use in horses intravenously.
- Allergy Testing: If your pet is scheduled for allergy skin testing, let your veterinarian know they are on this medication, as it needs to be stopped at least 4 days beforehand to ensure accurate test results.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.