I did a little research on Minocycline after Renee had mentioned that her new vet recommend it over Doxycycline. It looks like Minocycline may be a good alternative when Doxy just isn't cutting it. There are a couple of research papers toting its benefits from acting as an anti-inflammatory (like Doxy) and it shares many of the attributes and actions as Doxy.
I was surprised to also find out that Minocycline is able to penetrate tissues deeper than Doxycycline and that Minocycline has excellent lung tissue penetration superior to Doxycycline. Minocycline, like Doxy, can be given as a once daily dosage (at the guidance of a veterinarian as to what that appropriate therapeutic dosage is).
It looks like Minocycline is dosed much like Doxycycline at 5mg/kg - 10mg/kg PO BID. Considering that Doxycycline has been the staple antibiotic in treating Mycoplasmosis infections in rats for the past 20 years, I believe it may be safe to assume that mycoplasma pulmonis may have developed a resistance to Doxycycline. This has been discussed in recent veterinary literature (2016-2018) in that Minocycline is now recommended as a strong alternative to Doxycycline in the presence of mycoplasma pulmonis. Beans and Pi have a check-up today with their exotics vet, so I'll take the opportunity to discuss Minocycline during their appointment and I'll share any additional guidance/information here as well.
Here is a recent article from 2018 regarding Minocycline in the use of Veterinary Medicine and it discusses the usage and therapeutic benefit as well as its activity against gram negative and gram positive bacterium:
Side effects, drug interactions and administration are very similar to the other Tetracyclines. Greene and others suggest a dose of 5-10 mg/kg orally or IV twice daily for 7-14 days for most infections (as reported in Plumbs).
Recent studies by Dr. Mark Papich at NC State and Dr. Leah Cohn at University of Missouri (cat study), and with Dr. Marit Maaland of the University of Copenhagen (dog study) determined optimum doses to meet pharmacokinetic-pharmacodynamic (PK-PD) targets. These studies, based on pharmacokinetics in 6 cats and 6 dogs suggests the following doses:
Cats:
Start with 8.8 mg/kg (OK to round up to 10 mg/kg) orally, once daily. Also can give 50 mg per cat (one tablet or capsule), once a day. A single dose of 50 mg is higher than necessary, but allows for tablets or capsules to be used intact. Always flush with a bit of water or food to avoid esophageal lesions from the hydrochloride.
Dogs:
Use 5 mg/kg orally, twice daily for bacteria with MIC of 0.25 ug/mL or below, (most susceptible bacteria are in this range), and 10 mg/kg orally twice daily for bacteria with MIC of 0.5 ug/mL (some of the streptococci and Staph aureus may be this high).
Issues to keep in mind:
- Doses at the high end of the range may be more likely to make dogs vomit, in their experience. (Not sure about cats, but something to watch for.)
- Minocycline can also be given IV (but not likely because the vials are expensive). Use a dose of 5 mg/kg, once daily, but give slowly over at least 10 minutes.
- For compounding (e.g. mixing with some liquid vehicle) keep in mind that (similar to doxycycline) it is a highly unstable drug and will degrade quickly and rapidly lose its potency (particularly in UV light, room temperature, with any cations, etc.). The capsules could be opened and diluted just prior to administration.
- There is more toxicity to RBC's (hematocrit) at >10 mg/kg dose.
The oral absorption is almost 100% in people and is good in horses. In Dr. Papich’s study in dogs the oral absorption was approximately 50% in fasted dogs. There is no assurance that fed dogs would have the same absorption. Oral absorption in cats was approximately 62%. Minocycline is excreted partially in the urine; therefore, these doses should produce active concentrations in urine for treating urinary tract infections. Minocycline is more lipophilic than doxycycline and other tetracyclines. It is also less protein bound than doxycycline. These features predict that there is good penetration into the lungs, prostate, CSF, intracellular spaces, etc.
There is data to show that organisms such as Wolbachia are more susceptible to minocycline than other tetracyclines. A study done here at UC Davis years ago showed almost 81% coverage of Mycobactria from dogs compared to doxycycline (29%). It also covers Bordetella, Pasturella, Brucella, Coxiella, MRSP, Mycoplasma, etc. Some methicillin-resistant Staphylococcus may be resistant to doxycycline and other tetracyclines, but susceptible to minocycline. However, susceptibility testing is always needed to confirm susceptibility. Unless susceptibility tests confirm susceptibility, minocycline is not recommended as the drug of choice for gram negative infections caused by Enterobacteriaceae such as
E. coli or Klebsiella or for Anaerobic, Proteus, and Pseudomonas infections.