Diethylcarbamazine Citrate
Diethylcarbamazine acid citrate
Also known as: Hetrazan · Banocide · Diethizine · Filarcidan · Notezine · DEC · Diethylcarbamazine acid citrate · Diethylcarbamazini citras · Ditrazini citras · RP-3799
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 |
|---|---|---|---|---|---|
| Heartworm prophylaxis | 6.6 mg/kg PO once a day preceding infection and for 60 days following last exposure to mosquitoes. | PO | q24h | 60 days post-exposure | 🌎 NA |
| Heartworm prophylaxis | 6.6 mg/kg PO daily from beginning of mosquito season and for two months thereafter. | PO | q24h | Seasonal + 2 months | 🌎 NA |
| Heartworm prophylaxis | 2.5-3 mg/kg PO daily; begin prior to mosquito season | PO | q24h | Continuous | 🌎 NA |
| Heartworm prophylaxis | 5-7 mg/kg PO daily. Begin before infection is likely and continue 60 days after mosquito season. | PO | q24h | Seasonal + 60 days | 🌎 NA |
| Treatment of ascarids | 55-110 mg/kg PO | PO | Once | Single dose | 🌎 NA |
| Treatment of lungworms (Crenosoma vulpis) | 80 mg/kg PO q12h for 3 days | PO | q12h | 3 days | 🌎 NA |
- Heartworm prophylaxis: In dogs that become microfilaremic while on DEC, may continue, but do not interrupt daily DEC therapy.
- Heartworm prophylaxis: Should be given year-round in areas where mosquitoes are active throughout the year. Re-examine 3 months after starting therapy and at 6-month intervals for microfilaria.
- Heartworm prophylaxis: Some areas will require year-round treatment.
- Treatment of ascarids: Must not be used in microfilaria positive patients. May be used as a preventative for ascaridiasis when dosed at 6.6 mg/kg PO per day.
- Treatment of lungworms (Crenosoma vulpis): Must not be used in microfilaria positive patients.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Treatment of ascarids | 55-110 mg/kg PO | PO | Once | Single dose | 🌎 NA |
Ferrets
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Heartworm prophylaxis | 5.5 mg/kg PO once a day | PO | q24h | Continuous | 🌎 NA |
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Treatment of early stages of Dictyocaulus viviparous infestations | 22 mg/kg IM for 3 successive days; or 44 mg/kg IM once. | IM | q24h or Once | 3 days or Single dose | 🌎 NA |
- Treatment of early stages of Dictyocaulus viviparous infestations: DEC is available in an injectable dosage form containing 400 mg/mL in the U.K., no FDA-approved injectable form is available in the U.S.A.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Diethylcarbamazine citrate (DEC) is a piperazine-derivative anthelmintic that was historically the hallmark agent for daily heartworm disease prophylaxis in dogs.
- Current Status: Largely replaced by modern monthly macrocyclic lactones (e.g., ivermectin, milbemycin). It is no longer commercially available in veterinary oral dosage forms in the USA.
- Indications: FDA-approved for the prophylaxis of heartworm disease (D. immitis) and the treatment of ascariasis in dogs. It has also been used in ferrets, zoo animals, and for parasitic bronchitis in cattle and sheep (in the UK).
- Clinical Pearl: DEC must be administered daily for heartworm prevention, unlike newer monthly preventatives, which made owner compliance a historical challenge.
Mechanism of action
The exact mechanism of DEC is not completely understood, but it exhibits both direct paralytic and host-dependent immunomodulatory effects:
- Direct Paralysis: DEC acts as an agonist at nicotinic acetylcholine receptors (nAChRs) on the nematode somatic muscle → Depolarization of the muscle membrane → Spastic paralysis of the parasite.
- Immunomodulation: DEC alters the parasite's surface membrane (interfering with arachidonic acid metabolism) → Exposes hidden antigens → Enhances host immune system clearance of microfilariae.
Safety & warnings
Contraindications
- Dogs with circulating microfilaria (due to risk of severe shock-like reaction)
Adverse effects
- Vomiting
- Diarrhea
- Fixed drug eruptions (rare)
- Severe anaphylactoid reaction (in microfilaremic dogs)
- Hepatic injury (reported in cats)
Precautions
CRITICAL WARNING: DEC is strictly contraindicated in dogs with circulating microfilariae.
- Administration to microfilaremic dogs can trigger a severe, potentially fatal anaphylactoid (shock-like) reaction within 20 minutes to 2 hours. Signs include salivation, vomiting, ataxia, shock, and DIC.
- Always verify a negative heartworm test (specifically checking for microfilaria) before initiating therapy.
- If microfilaria are detected in dogs undergoing adulticide therapy while on DEC, stop DEC immediately until microfilaria are eliminated.
- Rare reports of infertility in male dogs exist, though controlled studies show no adverse effects on semen.
Drug interactions
Theoretical enhancement of toxic effects due to shared nicotine-like mechanism of action; use with intensified monitoring.
Theoretical enhancement of toxic effects due to shared nicotine-like mechanism of action; use with intensified monitoring.
Theoretical enhancement of toxic effects due to shared nicotine-like mechanism of action; use with intensified monitoring.
Monitoring
- Microfilaria status (prior to and during heartworm prophylaxis)
- Clinical efficacy (when used as an anthelmintic)
Pharmacokinetics
Absorption
Rapidly absorbed after oral administration, with peak serum levels occurring in about 3 hours.
Distribution
Distributed to all tissues and organs except fat.
Metabolism
Rapidly metabolized.
Elimination
Primarily excreted in the urine (70% of a dose within 24 hours) as metabolites or unchanged drug (10-25% of a dose).
Overdose
DEC is considered a relatively non-toxic compound with a wide margin of safety.
- Clinical Signs: Large overdoses generally result in self-limiting vomiting or CNS depression.
- Management: For very large, recent ingestions, consider GI decontamination (inducement of vomiting, activated charcoal, cathartics). If clinical signs occur, provide supportive care (e.g., IV fluids).
Available products
Formulations
- Tablets
- Injection (UK only)
Veterinary
- No oral products currently marketed in the USA (though 10 are FDA-approved).
- Injectable 400 mg/mL (Available in the U.K. only)
Human-labeled
- Diethylcarbamazine Citrate Tablets: 50 mg (Hetrazan®) - Available for compassionate use only.
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store in tight containers at room temperature and protect from light, unless otherwise specified by the manufacturer.
Client information
- Daily Administration: Unlike modern monthly heartworm preventatives, this medication must be given every single day to be effective. Give all doses exactly as directed by your veterinarian.
- Testing is Mandatory: Dogs must be checked for heartworm microfilaria before starting or restarting this medication in the spring. Giving this drug to a dog with an active heartworm infection can cause a fatal allergic reaction.
- Routine Screening: Dogs receiving this medication year-round should be tested for heartworms every six months.
- Administration Tip: Giving the medication with food or immediately after a meal may help prevent stomach upset.
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.