Pain Control In Dogs And Cats
you can read an article about long term pain control in arthritic dogs here.
You can read my thoughts on medical marijuana for your pet here.
Ron Hines DVM PhD
Lots of my articles are plagiarized and altered on the web to market products and services. There are never ads running or anything for sale with my real articles. Try to stay with the ones that begin with http://www.2ndchance.info/ in the URL box or find all my articles at ACC.htm.
You should never give your pet the medications I write about without expert, hands-on advice from your local veterinarian. Do not give doses higher than recommended. Do not give your pet medications that are sitting around your house and do not mix medications without first discussing it with your veterinarian. Any medication that is powerful enough to stop pain is also powerful enough to cause serious side effects when it is given to an animal for which it was not intended or in too large a dose.Your veterinarian job is to supply you with options and medications, you job is to decide which ones are working best in your pet.
All of us know that pets experience the same pain that we do. We will never be able to prove it, scientifically, but all of us who love our animals know instinctively when our pets are troubled, uncomfortable or in pain. Physicians have well designed plans to help their patient's in pain (ref) and Veterinarians are moving in that direction too (ref1, ref2)
The intimate bond between a pet and its master mean that you are the most likely person to notice those signs. It’s you, not your veterinarian, who needs to be your pet’s advocate when your pet is receiving veterinary care. And its you who has to decide when medications are working and when they are not.
Some pain is temporary (acute) and some is persistent (chronic). Your veterinarian has more medications at his/her disposal to treat acute pain in your pet than to treat chronic pain. (ref)
Acute pain results from surgery or sudden damage to any of the major organs, muscles or bones of your pet’s body.
Surgery, accidents and sudden organ inflammation are the most common cause of acute pain. Degenerative joint disease (arthritis) and cancer are the most common causes of chronic pain in pets.
All pain-relieving drugs are called analgesics. It’s not just a matter of making your pet more comfortable - controlling pain actually allows your pet to get well sooner. Whenever it is possible, it is better to give pain-controlling medications early rather than waiting until the pain becomes severe.
Pets and humans experience the same pain and react the same to pain-relieving medications. We can’t ask your pet how it feels; but we can ask human patients how much better they feel after receiving pain-control medications. That’s why, whenever I can, I make my decisions and recommendations on what works best in people.
Even then, pain is such a complicated phenomenon. So many things go into how you or your pet is feeling that it is extremely hard to decide the actual effect of any one thing. Even sex (ref1, ref2) sunshine (ref) and age (ref) influence reactions to pain.
I am convinced that dogs breeds that were bred to fight or perform heroically are more tolerant of pain. (It occurs in other animals)(ref)
When you take your pet to an animal hospital, your pet will be preoccupied, worrying about the strange scary environment. It may ignore the pain that you noticed at home. This can be very frustrating for owners who tell me “but he was limping at home!”
Signs of pain are more subtle and hard to notice in cats than in dogs. The most common sign of pain in cats is a reluctance to move. Some will hiss or growl when a painful site is touched. Others just become unresponsive to your affection. There are cats that become aggressive and belligerent when they are in pain and most will eat less. Many will groom more. Some carry their ears lower and others just meow pathetically.
In any pet, behavioral change, trembling, hiding, restlessness panting, salivation, licking of the lips , dilation of the eyes , aggressiveness, increased heart rate, loss of appetite, a tucked up tummy, lameness and limping or self-mutilation can all be signs of pain.
It is hard for veterinarians to judge the severity of your pet's pain, When I am uncertain, I often pinch the front toe of a pet that might be in pain to judge the severity of its pain. If the cat or dog reacts to the toe pinch as I would, then I assume the severity of its other pain is probably less than that of the pinch. We only have crude methods when our patients can't speak.
Pain alone can actually change the results of blood chemistry analysis. Dogs and cats in pain can have elevated blood sugar. Their blood cortisol (corticosteroid) and white cell levels often increase too. Pain can also interfere with your pet’s immune system, increase the risk of infections and slow the healing of wounds and surgical incisions. So removing your pet's pain is not just a matter of making it feel better - its important for it to get better.
The total elimination of pain may be impossible or even undesirable in your pet. Any medication that effectively blocks pain has undesirable side effects as well. But we can minimize pain in your pet with a number of medications.
There are five major classes of medicine that can be used to control pain in dogs and cats. Cats do not metabolize many of these drugs as well as dogs do, so safe options for your cat will be fewer and your veterinarian will be more cautious.(ref)
All of the medications I discuss must be used with extreme caution in cats. You and your veterinarian must weigh the advantages of pain medications in your cats against the possible damage that might occur.
There are some general rules when using pain control medications in dogs and cats. The first is to give the medication early, before the pain becomes too intense. The second is to give lower doses of two or more pain control medications that have different modes of action rather than a higher dose of a single medication. Often, what we call a "second tier" medication that is weaker but has fewer side effects is added to a "first tier" medication that is more powerful (but more dangerous) in order to keep the first tier drug dose low.
Doses need to always be kept to the bare minimum that gives your pet acceptable relief. Older patients generally need lower doses less frequently than younger, more robust, pets. Its also wise to check your pet's kidney and liver function before and during the use of most pain control medications.
The Non-steroidal Anti-inflammatory Agents (NSAIDs):
This section pretty much repeats the information in another article I wrote on managing arthritis in older dogs. That article discusses safer, non-drug , option to help pets in pain. You can read that article here.
Cats do not tolerate NSAIDs of any kind well. The only approved NSAD for cats in the United States is meloxicam (Metacam) ; and it is only approved for a single post-surgical injection to relieve pain. The dose must be exactly correct for the cat’s weight. If it is given longer to cats, it often causes severe kidney damage. Some of these unfortunate cats can be saved with intensive intravenous fluids given for a number of weeks, but some of them can’t (ref)
The Sides effects Of All NSAIDs
NSAIDs are all very effective in treating chronic pain. They work better when the pain is due to inflammation, such as arthritis, than when it is the nerve-generated pain of spinal cord disease.
All newer NSAIDs work well in dogs. All are relatively safe when they are given according to the manufacturers directions. But all have the potential to produce, occasional, severe side effects. Usually, those side effects occur when too much was given, when it was given too frequently, or when it was given combined with certain other medications. But sometimes, serious side effects occur when the NSAID was given exactly as the FDA-approved label on the product suggested.
All NSAIDs can have negative (harsh) effects on your pet's digestive tract. Although NSAIDs can affect many of your pet’s organs, its stomach and intestines are the most sensitive. When digestive tract problems do occur, your dog will probably loose its appetite. It may develop diarrhea and its stool may become dark and tarry (from digested blood).
NSAIDs also have the potential to slow your pet’s blood clotting process.This can leading to uncontrolled bleeding. Even pets that have no visible bleeding problems when taking NSAIDs have a slower blood clotting time. (ref)
NSAIDs affect the blood supply to your pet’s kidneys. So they can make existing kidney problems worse and possibly cause new ones.
NSAIDs should not be given when your pet is on certain other medications.
(Such as prednisone, dexamethasone or other corticosteroids,
It is safest to have a “rest period” between switching from one NSAID to another. We are never certain how long some of these drugs linger in your pet’s system.
I always try to give NSAIDs with food. You won’t see the drug effect on your pet immediately. Wait up to 8 hours to see full effects of the first dose and up to 10 days to see its long-term effect on your pet’s pain.
No one has ever proven that any one of the newer NSAIDs is more effective than another. But if one brand does not appear to be effective in your pet, try a different one. Absorbability and formulations differ between manufacturers and products. However, if you pet has had a severe side effect to any NSAID, be extremely cautious if you attempt to use another. If you give an NSAID medication in liquid form, be sure to shake the bottle well.
NSAIDs will, on rare occasion (perhaps one in 1500 dogs, no one really knows) , cause severe gastrointestinal bleeding liver or kidney damage. When it is the intestines that have been damaged, the pet will stop eating, vomit and have diarrhea and its gums might become pale (anemic). The problem with liver or kidney damage is that by the time signs are visible to you, the damage has already been done. Intestines are capable of rapid healing - livers and kidneys are not.
When it is the liver that is affected, the dog’s gums and the whites of its eyes may turn yellowish in color (jaundiced). When the kidneys have been damaged, the pet will become depressed (uremic). You can read about kidney disease and uremia here.
Although these type of problems are rare, they do occur and they are never “rare” when they occur in your pet. It is nearly impossible to predict which pet might experience these severe side effects. They can occur suddenly and without warning – but usually within the first few weeks of use. Dogs differ in how they metabolize NSAIDs. Fast metabolizers dispose of the drug rapidly - sometimes too rapidly to benefit from it. Slow metabolizers allow the drug to build up to toxic levels in their system. The vast majority of dogs are somewhere in the middle - and safe. You can read more about NSAID therapy that went wrong here.
A few dogs develop a dry eye problem (Keratoconjunctivitis Sicca) due to NSAIDs. These are often pets that already had marginal tear production and it is usually the NSAID drug, etodolac (Etogesic), that was implicated. (ref)
All pets receiving NSAIDs should have their blood chemistry/hematology profile run prior to beginning their pain medication. (So your veterinarian will have a reference point to refer to if drug issues develop later) It is safest to have those same tests repeated every six months to monitor how your pet is handling the medication – particularly its liver and kidneys.
You need to inform your veterinarian of any change in your pet after it begins NSAID treatment. When serious side effects occur, it is often that too much of the medication was given for the pet’s weight or that the pet was given additional medications (such as aspirin or Advil). But occasionally, side effects occur when you give the medication exactly as it was prescribed. When that happens, the dose needs to be lowered or another medication needs to be substituted. (Do not start giving NSAIDs after mid-week. Start on a Monday or Tuesday, so your veterinarian will be available if problems occur.)
I know I began with really scary side effects. Just remember, NSAIDs have an excellent track record for safety in dogs. Recent studies found that these medications boost the activity level of arthritic pets by 20%. (ref) The use of any drug is a trade-off between risks and benefits and the NSAIDs are no exception. The only way you will entirely avoid the risk of medication side effects is to use treatments that don’t do anything one way or the other - like Wellness-New Age medicine, naturopathic, homeopathic, complimentary and chiropractic medicines and therapy.
These alternative therapies do have real benefits for some pets and their owners - they keep the pet safe from the side effects of real drugs they did not really need, they avoid the dangers of over-medication and they offer comfort and emotional support to worried owners, concerned over the health of the pets they love.
What Are The Most Popular NSAIDs Available For My Pet ?
All NSAIDs decrease the body’s production of prostaglandins, one of the main drivers of inflammation, by blocking enzymes involved in prostaglandin formation (COX enzymes).
Modern NSAIDs are selective in which COX enzymes they block. The earlier, “first generation” NSAIDs, ones, like aspirin and ibuprofen, are not selective in which of the COX enzymes they block. The block the good with the bad, so they produce greater side effects. That is why I don't suggest that you give any of them to your pet. The only one I discuss is piroxicam (Feldene) because there are pet owners who just can't afford the safer, but more expensive, newer ones.
The modern NSAIDs block a specific COX enzyme (COX-2) that is chiefly involved in the production of inflammatory prostaglandins. These are the NSAIDs you see advertised for dogs.
There is no proof that any one brand is more effective, or causes less potential side effects than another.
This was the first modern NSAID to become available for dogs in the US (in 1997). It comes in injectable form, caplets and chewable tablets. It is sold by Pfizer. You can read the complete product label information for Rimadyl here . In 2005, it became available in generic (Novox) form.
Zubrin (tepoxalin, Schering-Plough/Merck/Intervet)
This NSAID was investigated as a possible anti-cancer medication in 1994. (ref) and several years later, as a possible anti-inflammatory drug for humans. (ref). The product has moved between manufacturers due to company acquisitions. You can read a partial product insert here (they don't seem to have gotten around to sending a more complete one to the FDA). Schering Plough promoted the concept that Zubrin was safer in dogs than its competitors, but the FDA soon put a stop to that. (ref)
Deramaxx (deracoxib, Novartis)
This medication was released in the United States for use in dogs in 2002. Although it was developed by Merck in its Rahway, NJ facility, it is currently marketed by the Swiss multinational pharmaceutical company, Novartis. You can read the full product label information that comes with Deramaxx here.
Metacam (meloxicam, Mobic, Mobicox-Canada Boehringer Ingelheim)
Boehringer Ingelheim was already studying this drug in 2000 as a potential anti-inflammatory drug in humans (ref) It was available for use in dogs in Europe and Canada from the early 1990s and in the US, from 2003. It is one of the few NSAIDs approved for one-time, one-injection, use in cats. You can read the full product label information that comes with the higher, 1.5mg/ml, Metacam here.
EtoGesic ( Etodolac Ft. Dodge/ Wyeth human form= Lodine)
Of all the NSAIDs approved for dogs, dry eye (although quite rare) is most associated with this one. (ref) If your dog is one of the breeds particularly susceptible to dry eye, or if it has already experience dry-eye in the past, a schermer tear test prior to beginning EtoGesic would be wise. You can read the full product label information for EtoGesic here .
Previcox (firocoxib Merial, Equioxx=horses)
Previcox is Merial’s entry into the dog NSAID market. It is the most recent one , having been approved in the US in 2007. (although it was already being used in European dogs in 2004) It is sold as a chewable tablet. Don't expect to see the full effect of Previcox for about a month after you begin giving it. (ref)
Although Merial developed the product specifically for dogs, it does not appear to be any better than carprofen or meloxicam in preventing pain and lameness (ref) . You can read the full product label information for Previcox here.
Flunixin meglumine (Banamine, Schering-Plough, etc)
Flunixin meglumine is a potent injectable NSAID, which is particularly good for intestinal pain. In the United States, it is approved only for use in livestock. Veterinarians have use it off-label to treating the pain associated with parvovirus intestinal disease in dogs and for treating post-surgical and stomach pain. It must be used very cautiously in cats. It is only FDA-approved for use in livestock. You can read the product label information here.
These are the first generations of NSAIDs. They include, piroxicam (Feldene), Aspirin (Bayer arthritis, acetylsalicylic acid) indomethacin (Indocin) , Advil (ibuprofen) and Aleve (naproxen).
They are all effective in eliminating arthritis inflammation and pain. The problem with all of them is that they do not selectively block COX-2 enzymes and dogs and cats are considerably more susceptible to their dangerous side effects than humans are.
Because they block protective COX-1 enzymes as well as "bad" COX-2 enzymes, they all of have a low (narrow) therapeutic index. A drug's therapeutic index is the difference between the dose that gets you the effect you want and the dose that causes harmful side effects. It means, that when you give your pet a first generation NSAIDs, the dose you have to give to gain relief will be close (and sometimes the same) as the dose that will produce toxic side effects. The only reason for using any of these medications is when you can not afford to use the safer NSAIDs that I listed above and which are FDA-approved for dogs.
If you do choose to use any of these older NSAIDs, you need to understand that the risks of serious, or even fatal, side effects are much greater. (Feldene/piroxicam is a legitimate treatment for certain tumors in dogs. In that case, your veterinarian decided the risks were worth it to save your pet's life)(ref)
Feldene is not approved by the FDA for use in dogs. But veterinarians are allowed to legally make their own decisions when prescribing approved human drugs for animals.
Although veterinarians chiefly prescribe it for dogs as a cancer treatment, some also use it in cases of arthritis pain and inflammation because it is so inexpensive - not all of their clients can afford the newer medications.
Feldene was developed for arthritis pain in humans. But because it is not selective in blocking COX enzymes, it has a greater potential to cause a number of bad side effects. When it was used in short cancer trials in dogs, a small percentage of the dogs that were on it for a relatively short time developed kidney damage. (ref1, ref2). That, intestinal bleeding, or liver damage, are its most dangerous potential side effects. The same general warnings that apply to all NSAIDs apply to Feldene. All that aside, there are dogs who tolerate Feldene well. You will just have to decide for yourself if potential benefits outweigh potential risks. Piroxicam is not an FDA-approved medication for pets, but you can read the human product label information here.
Aspirin (acetylsalicylic acid)
can find aspirin doses all over on the Internet. I don’t want
to print them because aspirin is so readily available that lots
of pet owners give it to their pets without veterinary supervision
and later encounter side effects that they regret. I do not want
to encourage that, or feel responsible for the consequences; so
I will leave that do-it-yourself advice to others. Aspirin is considerably
more toxic to cats than it is to dogs.
Tramadol is a medication that a lot of vets discuss recently as a possible safer option for pain control in your pet. It’s side effects seem to be considerably less than the potential ones of NSAIDs, traditional narcotics or corticosteroids. The medication is inexpensive.
Unlike NSAIDs, tramadol works directly on pain sensation in your pet's brain, not on the source of the pain itself. It is being used to control post-surgical pain and, sometimes chronic pain, in pets. Although it works on the same portions of the brain as narcotics, it is not considered a controlled substance by the DEA. That may soon change. (ref)
Tramadol has not been used in pets for very long. We know less about possible long-term toxicity when it is used in cats. Perhaps will turn out to be an effective alternative to NSAIDs. Pets with liver or kidney disease need lower doses of tramadol. Tramadol is not an FDA-approved medication for pets, but you can read the human product label information here.
Gabapentin is sometimes effective in controlling chronic pain in humans, particularly the neuropathic pain of spinal cord injury.
It might have a place in chronic pain management in pets as well. The one study I know of that looked at its use in dogs with acute pain, found it was not helpful. (ref) Another study looked at its use in cats subjected to thermal pain. It was not helpful there either. (ref) Gabapentin is not an FDA-approved medication for pets, but you can read the human product label information here.
Methocarbamol is a centrally acting muscle relaxant, not a pain-killing analgesic. But veterinarians occasionally dispense it when they think that muscle spasm might be a part of your pet’s problem. It is a safe medication. So if your pet suffers from spinal pain, you might discuss incorporating methocarbamol in its treatment plan. Methocarbamol is approved for use in dogs and cats. You can read the human product label information here.
Dissociative Anesthetic Agents:
Ketamine (Ketaset, Ketalar,Vetalar)
Veterinarians commonly use ketamine as a general anesthetic in cats. However, studies have found that it sometimes reduces pain when it is applied to the skin as a gel or paste. (ref) Specialty compounding pharmacies can formulate this gel. Ketamine's injectable form is FDA-approved for use in pets. You can read the product label information here.
Alpha-2 agonists or Blockers:
Xylazine is an injectable sedative and anesthetic that is approved for use in dogs. It belongs to a class called alpha-2 agonists. When given by intra muscular injection at less than anesthetic doses, it is a very effective pain reliever during surgical procedures. Higher doses commonly cause dogs to vomit and can cause dangerous decreases in respiration and blood pressure. I have not used Xylazine in cats, but others have. (ref) You may be able to read the product label information here.
Medetomidine hydrochloride (Domitor, Novartis Co)
Medetomidine hydrochloride is approved as an anesthetic and pain reliever for use in dogs recovering from surgery. In some parts of the World, it is used in cats as well. (ref)
Medetomidine also belongs in the class of drugs called alpha-2 adrenoreceptor agonists. At anesthetic doses this medication slows heart rate and respiration.(ref)
Medetomidine is metabolized by your pet's liver and excreted through its kidneys so it should not be given to dogs that have liver or kidney disease. It should also not be given to dogs at times that they are agitated and fearful at the animal hospital or dogs that might go into shock due to pre-existing disease. You can read the product label information here.
There has been recent interest among veterinarians in trying amantadine to control pain in pets. The drug was developed to treat Parkinson’s Disease in humans and also used in the treatment of influenza. It also appeared to be helpful in dealing with chronic back pain in humans. (ref)
It appears to sometimes be effective in blocking chronic pain in dogs and there is also some positive information on its use in cats. But I know of no controlled studies that have been performed. Your vet can try it and you both can decide if it seems to help. Amantadine is not FDA-licensed for use in pets, but you can read the human product label information here.
Amitriptyline Tricyclic antidepressant, (Elavil)
From studies in humans, we know that the tricyclic antidepressant, Elavil, is sometimes effective in reducing chronic pain. I have administered it to dogs and cats without serious problems. It might be helpful in controlling the pain of hyperesthesia syndrome in cats. (ref) although I have found megesterol more effective for that. Amitriptyline is not FDA-licensed for use in pets, but you can read the human product label information here.
Like muscle relaxers, corticosteroids (glucocorticoids) do not control pain. They are, however, the most potent anti-inflammatory drugs known.
All of the synthetic corticosteroids (prednisone, prednisolone, dexamethasone, etc.) mimic the effects of the body's own cortisol which is produced in your pet's two adrenal glands. (There is an explaination of that process in my article on Cushing's disease) However, all corticosteroids have major side effects when given over extended periods of time.
These changes include, weight gain, fluid retention , increased thirst and urination, thinning of the skin, liver changes, decreased resistance to infectious disease, mood swings, and increased blood sugar.
When they must be used, they should be given in the minimal amount that will control inflammation and they should not be given more than two or three times a week - at most. A few corticosteroids used in humans for nasal allergies and one, beclomethasone, that is used on dogs topically can be applied every day. But they normally have very limited or no effects within the body. Side effects on corticosteroids can be managed and weight control is critical. They are a legitimate end-stage option when owners and pets want a few more pain-free months together. At lower doses, pets can be maintained on corticosteroids for long periods of time - just as humans are. (ref)
Controlled Medications (Narcotics)
Opiates or Opioids are the most powerful pain-relieving compounds available for pets. They all mimic natural brain chemicals that limit the perception of pain. However, they are highly addictive and should be reserved for pain that will not respond to other medications. . Also, with time, doses have to be increased to obtain comparable pain relief. Side effects can include bizarre behavior similar to the euphoria (joyous feeling) seen in humans taking these meds, depression of breathing, physical dependence, slowed heart rate constipation and itching.
Opiate narcotics may also cause contraction of the pupils of the eyes, sedation and unusual taste in foods. In humans, they are generally given to alleviate the pain of terminal cancer or painful nerve conditions. In pets, they are given to lessen post-surgical pain, and the pain of trauma, or to combat the pain of arthritis and cancer when all other medications fail.(In dogs in late hip dysplasia, corticosteroids are more likely to be given )
Injectable and oral forms of opiates are rarely dispensed for pets in the United States. In the US, the Drug Enforcement Agency (DEA) frowns on any long-term use of opioids, fearing they might be diverted to illegal human use. The DEA lists all the strong opiates as CII (Class-2 narcotics). Most veterinarians fear prosecution by the DEA and use them as briefly in pets as possible. Because cats are deficient in glutathione liver enzyme, the half-life of some opioids in cats may be prolonged and doses must be considerably smaller.
Fentanyl Patches (Duragesic Janssen Pharma)
Veterinarians use this narcotic to alleviate post-surgical pain in pets (ref) and to treat the pain of terminal cancer. It is about 100 times stronger than morphine.
Only a few veterinarians dispense it for severe arthritis when NSAIDs fail. Most would rather gain a few more months of pain-free life for your pet by giving it corticosteroids. However, fentanyl has advantages in many dogs and cats over corticosteroids in relieving end-stage pain.
Fentanyl is not a drug to be used in your pet lightly. It is not, and never will be , a first line treatment for arthritis. But it can be a last ditch treatment for your pet to gain precious pain-free time.
After a fentanyl patch is applied to your pet’s skin, its intense analgesic (pain-canceling) power can block pain for up to three days.
There is a price to pay for that. Fentanyl is an opioid narcotic. All opioid narcotics can cause mood changes, sedation or restlessness in pets and humans. They are also powerful depressors of respiration and the nervous system, so your pet can pass away from respiratory failure (not breathing adequately) or circulatory collapse if the dose is too high or your pet is already too debilitated and weak. There is an antidote for these effects – Naloxone (Narcan). So pets placed on fentanyl should be hospitalized under close watch for the first 48 hours after beginning the patch or the dose should begin very low and only be increased very gradually over a period of weeks.
All control narcotics can cause mood change (dysphoria), whining and restlessness or depression and these are the side effects that bother pet owners most. Sometimes these problems lessen over time as the pet becomes used to the medication.
Dogs that are running fevers can absorb the drug too quickly from the patch and any form of external heat (such as a heating pad) – can release it suddenly. Other drugs your pet may be taking can also influence how fentanyl affects your dog. (Cushing’s and cognitive dysfunction medications, mood-altering drugs, tranquilizers, sedatives etc.)
Dogs are resistant to the effects of all opioids. So typical human doses have no bearing on what an effective dose will be in your pet.
Being a federally controlled substance, there is a lot of paperwork involved for your veterinarian and you will have to deliver and pick up the fentanyl prescription in person at your pharmacy.
Patches may cause irritation to the skin where they are applied. That problem tends to get worse with time, but it can be managed with soothing ointments. The patch is very dangerous if your pet swallows it. You can read the most extensive review of its use in dogs and cats here. There is a great deal of variation between pets in the amount of medication they will absorb so always begin by giving your pet less than you think it will need. (ref)
Fentanyl patches are not FDA-licensed for use in pets, but you can read the human product label information here.
On 6/25/2012, Elanco, the US pet health division of Eli Lilly, obtained FDA approval to market fentanyl as a topical liquid to relieve pain in pets. This product relies on technology developed by an Australian pharmaceutical company, Acrux Ltd. It was approved for use in pets in the EU in 2011. You can read the only information I have available at this time here. If it works as hoped and doesn't encounter too much opposition from the DEA, it might be a considerably better way to use fentanyl on pets then the current skin patches that animals can remove or even eat accidentally. This new technology is based on a fast- drying, small volume of fentanyl-containing liquid, that contains penetration enhancers, that when applied topically, deposit drug into the pet's skin for long acting transdermal delivery to its bloodstream. I could find nothing on the FDA website about the product but I believe it will be labeled for the control of post-operative pain as a single dose that might give pain relief for 4 day. ( How frequently vets choose to use the product and what the government will allow remains to be seen - unfortunately, the use of these highly effective pain medications are mired in politics, national narcotitcs policy and the resulting uneasiness and fear on the part of practitioners that consider prescribing them.)
Morphine (Oramorph SR, Roxane)
Morphine sulfate (a CII regulated narcotic) is available in tablet, liquid and capsule preparations. Cats have been given the liquid formula - but most cats and some dog strongly dislike the bitter taste. I have never used this drug in my practice, although I saw it used when I was in veterinary school. Although it is a centuries-old drug, it is rarely used in animals in the United States. It is a very effective barrier to pain. Morphine was usually given to dogs by injection. It went into disfavor because clients occasionally took the pet’s medication themselves and because of strong government opposition to it’s use. This is because of the stigma of narcotics addiction in humans. Also, because the dog dose is so much higher than the human dose, owner fatalities occurred when the tablets were dispensed for dogs but taken by the pet owner. Morphine is not FDA-licensed for use in pets, but you can read the human product label information here.
This is an injectable narcotic drug that is one fifth as powerful as morphine. It is an excellent drug for controlling pain for short periods in dogs. I have used it to spare dogs that were critically injured by automobile and had no hope of recovery. It gave these pets relief from pain until the owners could except the situation. I have not used it in cats. It is not suitable for long term use because, with time, pets become resistant to its action. Meperidine is not FDA-licensed for use in pets, but you can read the human product label information here.
Buspirone is a highly effective medication when used for treatment of anxiety and PMS syndrome in humans. It is very safe when given at correct dosage. More recently, it has been evaluated for its pain-relieving effect. In experimental rats, it was effective in blocking the pain of burns, wounds and inflammation. These data suggest the potential use of buspirone in the management of various types of pain. I place it here because it acts on the same mu receptors through which the opium narcotics block pain. Until now, it has been used in dogs and cats to decrease phobias and generalized anxiety. Buspirone should not be used along with the MO class of antidepressants because dangerous increases in blood pressure can result. The medication is not FDA-licensed for use in pets, but you can read the human product label information here.
Butorphanol (Stadol, Torbutrol, Torbugesic-SA, Ft. Dodge/Wyeth)
This mixed pain-receptor blocker is weaker than many narcotics, so, it is less likely to cause some of the respiratory depression that stronger narcotics may. Because of its greater safety, it is a bit more loosely regulated by the DEA (C-IV).
It is not used much to treat chronic pain in pets because its effects are so short-lived. This is one of the few opioid drugs that works consistently well in cats. It can be administered by injection or intranasal spray. It has been given to dogs and cats by injection, up to three times a day. It takes about 20 minutes for its pain-controlling properties take effect and lasts for about eight hours. It can also be given by mouth. It causes fewer side effects than traditional opioids narcotics.
Occasionally, butorphanol will cause eye dilation, confusion and pain at the site of injection - especially when given to cats. It is not considered to be useful in the management of chronic pain. Compounding pharmacies can prepare a transdermal gel of butorphanol that can be applied to the inner surface of your pet's ear or a shaved spot on the neck. The injectable liquid butorphanol has also be given orally to cats. Since it has no taste, cats will not fuss about a bitter taste. It is not absorbed well when given in this manner to dogs. Possible side effects are loss of appetite, vomiting, incoordination, and restlessness.
Butorphanol is also a good cough suppressant. It’s effect is similar to codeine. It is a good post-surgical medication for cats. Butophanol is FDA-licensed for use in pets, you can read the product label information here.
Buprenorphine (Buprenex, Temgesic, Vetergesic, Buprenex)
narcotic is about equal to tramadol in effectiveness (ref)
It has been used to releave post-surgical pain in dogs. (ref)
There are many other approaches to short-term relief of surgical pain in pets that I do not have the space or time to cover. On of them are nerve blocks with long acting numbing agents, like bupivacaine. (ref)
God did not give our pets exceptionally long lives. But he did bless them in other ways: They do not worry about tomorrow or fret about yesterday like you and I do. They live in the here and now. That, and their devotion, is why we love them so much. Sometimes, all your pet really needs in its Autumn years is extra love, and some of the non-drug suggestions in my article on arthritis.
What Might The Future Hold To Control Pain In Our Pets ?
Almost all of the effective pain control medications I have mentioned, work on your pet's brain to reduce or eliminate the sensation of pain. But in doing so, they can produce many side effects. There is a second approach. Pain travels to your pet’s brain via specialized nerve receptors (Nav1.7 and Nav1.8 ion channels) located throughout its body. I have noticed that certain breeds of dog, such as Labrador retrievers, perceive the pain of vaccinations less than others such as Chihuahuas. That could well be due to differences in those channels. We already know that pain perception differs substantially between humans. (mutations in a gene called SCN9A)
Theoretically, medications that target the Nav system rather than the brain should not cause many of the common side effects of current pain medicines. The US Department of Veterans Affairs hopes so, and is currently sponsors research at the Yale Center for Neuroscience searching for new medications that can do just that. They, or others, will likely succeed in the not-to-distant future. You can read a fairly current summary of current research in this area here.