Minocycline

Minocycline is a tetracycline antibacterial used extra-label for selected susceptible infections in veterinary patients. Its applications overlap with doxycycline, including some vector-borne infections and skin disease. Certain staphylococcal isolates resistant to doxycycline retain minocycline susceptibility, making organism-specific testing clinically useful. Its intracellular distribution supports activity against susceptible intracellular pathogens.

Group

Tetracycline antibacterial

Mechanism of Action

Minocycline reversibly binds the bacterial 30S ribosomal subunit and prevents aminoacyl-transfer RNA from accessing the acceptor site. This interrupts peptide-chain elongation and protein synthesis, usually producing a bacteriostatic effect. Its physicochemical properties permit activity despite some tetracycline efflux mechanisms. Intracellular exposure supports activity against susceptible Ehrlichia, Rickettsia and Wolbachia organisms.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Susceptible bacterial infection	5 mg/kg	PO	Every 12 h	Sufficient for many susceptible organisms.
Higher-MIC susceptible infection	10 mg/kg	PO	Every 12 h	Higher vomiting risk than the lower-dose regimen.
Susceptible bacterial infection	2.5 mg/kg	IV	Every 12 h	Half the 5 mg/kg oral regimen, as directed by the reported guidance for IV treatment; use a properly diluted infusion.
Higher-MIC susceptible infection	5 mg/kg	IV	Every 12 h	Half the 10 mg/kg oral regimen; use a properly diluted infusion.
Ehrlichia canis infection	10 mg/kg	PO	Every 12 h	Up to 28 days; Indication-specific 10 mg/kg PO every 12 hours for 28 days; the earlier inferred 5 mg/kg assignment was not supported by the indication-specific entry. Clinically compatible disease plus supporting test; IV is an uncommon alternative.
Susceptible soft-tissue or urinary infection	5–12 mg/kg	PO, IV	Every 12 h	Up to 14 days; Course 7-14 days; this source permits the same nominal range for IV and PO, unlike the earlier half-oral-dose IV alternative.
Nocardia or Actinomyces adjunct	5–25 mg/kg	PO, IV	Every 12 h

Cats

Use / stage	Dose	Route	Schedule	Instructions
Susceptible bacterial infection	8.8 mg/kg	PO	Every 24 h
Susceptible bacterial infection	50 mg/animal	PO	Every 24 h	Separate fixed-dose alternative; choose according to patient size and tolerance.
Nocardia or Actinomyces adjunct	5–25 mg/kg	PO, IV	Every 12 h
Atypical cutaneous mycobacterial infection	5–12.5 mg/kg	PO, IV	Every 12 h
Haemotropic mycoplasmosis	6–11 mg/kg	PO	Every 12 h	Up to 21 days

Horses

Use / stage	Dose	Route	Schedule	Instructions
Susceptible bacterial infection	4–5 mg/kg	PO	Every 12 h
Susceptible bacterial infection	2.2 mg/kg	IV	Every 12 h	Appropriately diluted infusion.

Indications

Treatment of selected susceptible bacterial skin, soft-tissue, respiratory or joint infections in dogs and cats.
Treatment of minocycline-susceptible staphylococcal infections, including selected isolates with resistance to other tetracyclines.
Treatment of selected canine ehrlichial or rickettsial infections.
Alternative Wolbachia-directed treatment during canine heartworm management when a supported minocycline regimen is selected.

Contraindications

Repeated tetracycline exposure in growing animals may affect teeth; individual risk requires assessment.
Pregnancy, nursing or animals under 6 months warrant particular caution due to tetracycline developmental effects; avoid with tetracycline hypersensitivity. Oliguric renal failure may require adjustment.

Interactions

Calcium, iron, magnesium and aluminium can reduce oral absorption.

Adverse effects

Nausea, vomiting and diarrhoea, more frequent at higher doses

Toxicity

Assess gastrointestinal signs and stop excess exposure; support hydration as needed.

Preparations

Preparation	Form	Strength	Route
Minocycline 50 mg capsule	Capsule	50 mg / capsule	PO
Minocycline 75 mg capsule	Capsule	75 mg / capsule	PO
Minocycline 100 mg capsule	Capsule	100 mg / capsule	PO
Minocycline 10 mg/mL oral suspension	Oral Liquid	10 mg / mL	PO
Minocycline 100 mg powder for injection Reconstitute and then dilute for infusion using the exact product instructions.	Injection	100 mg / vial	IV

Monitoring and Administration

Use culture and susceptibility where feasible. In horses, tetracycline susceptibility is not a reliable surrogate for minocycline.

In dogs, give at least 30 minutes before food if tolerated for better absorption.

Reconstituted injectable product requires further dilution before infusion; published guidance describes 5 mL initial reconstitution followed by 500-1000 mL diluent, with 24-hour room-temperature use period. Follow the actual vial instructions.

Canine Brucella combinations use minocycline 25 mg/kg PO daily for 4 weeks with gentamicin 5 mg/kg SC daily during weeks 1 and 4, or minocycline 25 mg/kg daily for 14 days plus dihydrostreptomycin 5 mg/kg IM twice daily for 7 days in singly housed neutered dogs. Clearance and relapse require serial assessment; monitor renal function with aminoglycosides. These are not minocycline-only eradication claims.