# Diethylcarbamazine (DEC): veterinary dose and monograph

> Diethylcarbamazine (DEC) is a veterinary antiparasitic. Piperazine-derivative microfilaricide. Indications include canine heartworm (Dirofilaria immitis) PREVENTION — daily, in microfilaria-negative dogs; ascarid (Toxocara/Toxascaris) infections; lungworm and certain other nematodes. This monograph lists 6 reference doses for dogs, cats, cattle and ferrets, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

Source: https://vetmasterji.com/drugs/diethylcarbamazine · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Antiparasitic
- **Also known as:** DEC, Hetrazan, Banocide, Carbamazine citrate
- **Species with doses:** Dogs, Cats, Cattle and Ferrets
- **General dose range:** 6.6 mg/kg PO q24h (daily during mosquito season) — check the species tables for the indication
- **Routes:** PO, IM
- **Last reviewed:** 1 October 2026

## Indications

- Canine heartworm (Dirofilaria immitis) PREVENTION — daily, in microfilaria-negative dogs
- Ascarid (Toxocara/Toxascaris) infections
- Lungworm and certain other nematodes
- Human/zoonotic lymphatic filariasis (context — Wuchereria, Brugia)

## Diethylcarbamazine (DEC) dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Diethylcarbamazine (DEC) doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Heartworm prevention (microfilaria-NEGATIVE dogs) | 6.6 mg/kg | PO | q24h | — |
| Ascarids | 55–110 mg/kg | PO | single dose | — |
| Lungworm (Crenosoma vulpis) | 80 mg/kg | PO | q12h | 3 days |

- Heartworm prevention (microfilaria-NEGATIVE dogs): Papich 5e and Plumb’s p.394: 6.6 mg/kg PO once daily from before mosquito exposure until 60 days after the last exposure (year-round where mosquitoes persist); recheck for microfilariae at 3 months and every 6 months. Never start in a microfilaraemic dog (severe reactions); if a dog becomes microfilaraemic on DEC, do not interrupt daily dosing.
- Ascarids: Papich 5e and Plumb’s p.394 (Todd 1985): 55–110 mg/kg PO as a single treatment (the 110 mg/kg dose may be split twice daily). Microfilaria-negative dogs only.
- Lungworm (Crenosoma vulpis): Plumb’s p.394 (Todd 1985): 80 mg/kg PO q12h for 3 days. Microfilaria-negative dogs only.

### Cats

*Diethylcarbamazine (DEC) doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Ascarids | 55–110 mg/kg | PO | single dose; repeat in 10–20 days | — |

- Ascarids: Papich 5e and Plumb’s p.394 (Todd 1985): 55–110 mg/kg PO; repeat in 10–20 days to remove immature worms.

### Cattle

*Diethylcarbamazine (DEC) doses for cattle*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Lungworm (Dictyocaulus) — early stages | 22 mg/kg | IM | q24h × 3 days (or 44 mg/kg once) | — | Withdrawal NOT established — treat as extra-label |

- Lungworm (Dictyocaulus) — early stages: Plumb’s p.394 (Brander 1982): 22 mg/kg IM for 3 successive days, or 44 mg/kg IM once, using the injectable (400 mg/mL, UK) — no approved US injectable. Oral use in cattle is not described. Obtain a withdrawal from the local label or FARAD.

### Goats

*Diethylcarbamazine (DEC) doses for goats*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| No reference dose for this species | Not established in Papich 5e or Plumb’s 10e — do not extrapolate from another species | — | — | — | — |

- No reference dose for this species: The previous goat row copied the cattle dose (‘as for cattle’); neither Papich 5e nor Plumb’s gives a goat dose.

### Sheep

*Diethylcarbamazine (DEC) doses for sheep*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| No reference dose for this species | Not established in Papich 5e or Plumb’s 10e — do not extrapolate from another species | — | — | — | — |

- No reference dose for this species: The previous sheep row copied the cattle dose (‘as for cattle’); neither Papich 5e nor Plumb’s gives a sheep dose.

### Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

*Diethylcarbamazine (DEC) doses for buffalo*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Lungworm (Dictyocaulus) — early stages | 22 mg/kg | IM | q24h × 3 days (or 44 mg/kg once) | — | Withdrawal NOT established — treat as extra-label |

- Lungworm (Dictyocaulus) — early stages: Plumb’s p.394 (Brander 1982): 22 mg/kg IM for 3 successive days, or 44 mg/kg IM once, using the injectable (400 mg/mL, UK) — no approved US injectable. Oral use in cattle is not described. Obtain a withdrawal from the local label or FARAD.

### Ferrets

*Diethylcarbamazine (DEC) doses for ferrets*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Heartworm prophylaxis | 5.5 mg/kg | PO | q24h | — |

- Heartworm prophylaxis: Plumb’s p.394 (Randolph 1986): 5.5 mg/kg PO once daily.

## Contraindications

Microfilaria-positive dogs (risk of fatal shock reaction). Existing adult heartworm infection without prior work-up. Known hypersensitivity. Onchocerca-endemic settings in people require caution (Mazzotti reaction) — relevant context.

## Species-specific warnings

> **Caution:** Dogs: Fatal anaphylactoid reactions occur if DEC is given to a heartworm-microfilaria-positive dog. Confirm a negative test before use, every time.

## Adverse effects

- Anaphylactoid/shock reaction if given to microfilaraemic dogs (vomiting, collapse, death)
- GI upset (vomiting, diarrhoea)
- Lethargy
- Hypersensitivity-type reactions from dying microfilariae (Mazzotti-like)

## Drug interactions

- Other microfilaricides: additive reaction risk if microfilariae present
- No major pharmacokinetic interactions of clinical note in dogs

## Pregnancy and lactation

Considered usable in breeding dogs at preventive doses; verify negative heartworm status first. Human data in pregnancy are reassuring but generally deferred in mass-drug-administration programmes.

## Monitoring

- Heartworm antigen + microfilaria test BEFORE starting and at least annually
- Strict daily compliance (a missed period leaves a prevention gap)
- Clinical signs of reaction after the first doses

## Toxicity and overdose

At preventive doses DEC has a wide margin. The dominant danger is not direct drug toxicity but the immune/anaphylactoid reaction to rapid microfilarial death in an infected dog — hypotension, collapse and death can follow a single dose. Overdose otherwise causes GI signs and lethargy.

Management: For an anaphylactoid reaction in a microfilaraemic dog: emergency therapy — IV fluids, epinephrine, corticosteroids, antihistamine, oxygen and supportive care. For simple overdose: symptomatic/supportive (anti-emetic, fluids). No specific antidote.

## Clinical pearls

- Golden rule: test heartworm-negative BEFORE the first DEC dose — never give to a microfilaraemic dog
- Largely superseded by monthly macrocyclic-lactone preventives, but cheap and still used where those are unavailable
- Owner compliance is the weak point — daily dosing all season is required for protection
- In India DEC is ubiquitous as the human antifilarial — easy to source, but the canine work-up rule still applies

## Mechanism of action

Not fully defined: it immobilises microfilariae and alters their surface so the host immune system (and hepatic/splenic clearance) destroys them, and it interferes with arachidonic-acid/eicosanoid metabolism in the parasite and host endothelium. It is microfilaricidal and active against developing larvae but does not reliably kill adult heartworms.

## Formulations and products

- 50 mg tablet
- 100 mg tablet
- Syrup 120 mg/5 mL (24 mg/mL)
- DEC vet preventive tablets (Various (India)) — Diethylcarbamazine citrate, Oral tablet
- Banocide Forte — 100 mg tablet, Tablet (human-label)
- Hetrazan — 50 / 100 mg tablet; syrup, Tablet / syrup (human-label)

## Storage

Tablets/syrup: 15–30 °C, protect from light and moisture.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Diethylcarbamazine (DEC) for dogs?

Reference doses for Diethylcarbamazine (DEC) in dogs: 6.6 mg/kg PO q24h (Heartworm prevention (microfilaria-NEGATIVE dogs)); 55–110 mg/kg PO single dose (Ascarids); 80 mg/kg PO q12h for 3 days (Lungworm (Crenosoma vulpis)). Confirm against the label and the patient before use.

### What is the dose of Diethylcarbamazine (DEC) for cats?

Reference doses for Diethylcarbamazine (DEC) in cats: 55–110 mg/kg PO single dose; repeat in 10–20 days (Ascarids). Confirm against the label and the patient before use.

### What is the dose of Diethylcarbamazine (DEC) for cattle?

Reference doses for Diethylcarbamazine (DEC) in cattle: 22 mg/kg IM q24h × 3 days (or 44 mg/kg once) (Lungworm (Dictyocaulus) — early stages). Confirm against the label and the patient before use.

### What is the withdrawal period for Diethylcarbamazine (DEC)?

Cattle, IM (Lungworm (Dictyocaulus) — early stages): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Diethylcarbamazine (DEC) not be used?

Microfilaria-positive dogs (risk of fatal shock reaction). Existing adult heartworm infection without prior work-up. Known hypersensitivity. Onchocerca-endemic settings in people require caution (Mazzotti reaction) — relevant context.

### What are the side effects of Diethylcarbamazine (DEC) in animals?

Anaphylactoid/shock reaction if given to microfilaraemic dogs (vomiting, collapse, death); GI upset (vomiting, diarrhoea); Lethargy; Hypersensitivity-type reactions from dying microfilariae (Mazzotti-like).

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.