Introduction

Doramectin is a macrocyclic lactone antiparasitic drug produced through fermentation by a genetically modified strain of Streptomyces avermitilis, with cyclohexanecarboxylic acid incorporated during biosynthesis. First introduced in the 1990s, it is widely used for endoparasite and ectoparasite control in swine and ruminants, offering:

• Broad-spectrum activity

• High plasma concentrations

• Extended duration of action

• Ease of administration

This article summarizes doramectin’s pharmacological properties and clinical applications, with reference to the injectable doramectin formulation produced by Huisheng Biotechnology.

1. Chemical Structure

Doramectin belongs to the avermectin family of macrocyclic lactones, structurally similar to ivermectin (Figure 1). Key differences:

• Doramectin: Features a cyclohexyl group at C25, a double bond between C22–C23, and uniform molecular composition.

• Ivermectin: A mixture of B1a (80%; C25 = CH(CH₃)C₂H₅) and B1b (20%; C25 = CH(CH₃)CH₃), with a single bond at C22–C23.

2. Pharmacological Advantages

2.1 Enhanced Pharmacokinetics

• Peak plasma levels: 2× higher than ivermectin (Figure 2).

• Effective duration: 18 days (vs. 12 days for ivermectin), due to:

  • Nonpolar cyclohexyl group at C25 improving lipid solubility.

  • Oil-based adjuvant formulation prolonging release.

2.2 Intramuscular Administration

• Ivermectin requires subcutaneous injection (challenging in large swine due to restraint needs).

• Doramectin’s IM route significantly improves workflow efficiency.

3. Clinical Significance for Swine Sarcoptic Mange

3.1 Sarcoptes scabiei Lifecycle

• Stages: Egg → larva → nymph → adult (completed in 8–15 days, avg. 12 days).

• Short-acting drugs (e.g., some ivermectin formulations):

  • Fail to cover the full lifecycle → reinfection risk.

  • Frequent retreatments promote parasite resistance.

3.2 Doramectin’s Long-Acting Benefit

• Single dose covers 12+ days, disrupting the entire lifecycle.

• Aligns with global consensus (Lanusse et al., 2009) to minimize dosing frequency and delay resistance.

4. Swine Farm Protocols

4.1 Dosage

• 1% injectable solution: 1 mL per 33 kg BW (300 μg doramectin/kg), IM.

4.2 Recommended Programs

Preventive Use:

• Sows: 7–14 days pre-farrowing.

• Gilt: 7–14 days pre-breeding.

• Boars: Twice yearly.

• Piglets: At weaning or nursery transfer.

Therapeutic Use:

• Infected pigs: Two doses 20 days apart.

5. Product Recommendation

Huisheng Doramectin 1% Injection:

• Validated efficacy against gastrointestinal nematodes, lungworms, lice, and mites.

• Flexible IM administration reduces labor stress.