Uncommon Solutions to Problems Dosing a Commom Drug - Metronidazole

Metronidazole is a drug that is commonly prescribed in humans to combat various anaerobic bacteria and protozoa.  It is also routinely prescribed for the treatment of amebic dysentery.  Metronidazole is available both in generic tablets and under the brand name “Flagyl” (Searle.)  Tablets sizes are 250mg and 500mg.

Metronidazole is also used by veterinarians to treat bacterial infections as well as giardia in dogs and cats.  Unfortunately, giardia is quite common in animals that often drink from stagnant pools of water, or ingest slugs, or have contact with other infected animals.

Although these conditions are easily treatable with metronidazole, there are several administration problems.  First, the commercially available tablets are often too large.  A child often would often be prescribed 100mg or less.  A typical dose for a cat would be 50mg; for a kitten only 25mg.  Dividing a tablet in 5ths or 10ths is impractical.  A very rough approximation of the dose is the best that could be accomplished.  A better option is having the drug compounded into the exact dose required in small gel capsules.

The second problem with dividing a metronidazole tablet is the taste - extremely bitter and often compared to battery acid!  Preparation of metronidazole in capsules is one solution since the capsule would enclose the bitter drug.  Island Pharmacy Services has been compounding metronidazole in a wide range of capsule sizes since 1990.  Please call 800-328-7060 for additional information on specific doses.

However, capsules are sometimes not a practical option for very small children or animals.  The best option would be an oral liquid.  Unfortunately, simply dissolving metronidazole tablets does not cover the taste and may actually make it worse!  For the past several years, IPS has been able to offer a practical alternative.  We stock a form of metronidazole that is insoluble - in other words, it does not dissolve in liquids and so does not present the same bitter taste of the tablets.  This chemical, metronidazole benzoate, can be compounded in oral suspensions of various strengths to deliver the same dose as a tablet or capsule.  In addition to eliminating the terrible taste, IPS can also add flavors to the liquid to make the suspension even more palatable.

Note:  Recently some veterinarians have expressed concern about using the benzoate form of metronidazole in cats.  The concern is toxicity associated with exposure of cats to drugs containing benzene rings.  While this concern must be acknowledged from a theoretical standpoint, our experience at IPS has not identified a practical problem in the administration of metronidazole benzoate.  There are probably many reasons for this evidence to the contrary.  First of all, IPS has compounded thousands of doses of this drug.  The great majority of doses are prescribed to address a specific condition, and when the condition has been treated the prescription is discontinued.  Therefore, the overall exposure to potentially harmful benzenes is limited.  Another justification expressed by our client veterinarians is that the potential exposure to benzenes is of far lesser importance than the treatment provided by the metronidazole dose.  In other words, metronidazole benzoate may be the only practical means of treating many cats and the alternative is ultimately the death of the animal.

Metronidazole is a potent drug used to treat a wide range of infections.  Based on IPS’s ability to compound small doses in capsules and suspensions, doctors and veterinarians now have another tool available to treat children and pets.  Questions regarding metronidazole or other drugs are always welcome.  Please call the Compounding Specialists at Island Pharmacy Services toll-free at 800-328-7060.  

references:  

Drug Facts and Comparisons , 1998, p.353a-353c, 400-401  

Veterinary Drug Handbook , Donald C. Plumb, Pharm. D, 2nd Edition, p.451-454  

Pharmacist’s Letter , Therapeutic Research Center , 1997, #131017  

Pricing For Metronidazole Compounded Doses:  

Metronidazole capsules are compounded in any size required.  “Typical” doses are 25mg (1/10th tablet), 50mg (1/5th tablet), 62.5mg (1/4th tablet), etc.  The average cost for capsules is $42.00 per 100.  

Metronidazole can also be compounded in a palatable suspension using an insoluble form of the drug.  This suspension avoids the terribly bitter taste of the raw drug.  In addition, flavors can also be added to make the liquid good tasting to the patient.  Flavors include bubble gum, liver, cherry, fish, and more.  The cost of the suspension varies widely depending on the concentration required and the quantity needed.  In general, the larger the quantity the less cost per dose.  However, where the capsules have an expiration date of 1-year, the suspension expires in 6-months.  Please call IPS at 800-328-7060 for an exact price quote on the dose and volume required.