There is a reason your dog's veterinarian asks you what medications, including supplements, you are currently giving to your dog; medications and supplements have side effects and interact with each other. But they also interact with the nutrients in your dog's food, which can cause the depletion of essential minerals and vitamins.

Interactions between prescription medications and nutrients can cause severe consequences and harm your dog's overall health. Anytime a drug or vaccine is provided, there is a negative impact on the ability of your dog's body to properly utilize nutrients, usually because it causes an interruption of nutrient absorption.

Your dog has a very complex metabolic system that relies on each organ system to work together to maintain a healthy body. All of the nutrients a dog consumes interact together, so if one vitamin or mineral is out of balance, there is a cascading effect on the entire system. 

When your dog is given prescription medication or other pharmaceuticals, side effects occur because the action of the drugs disrupts the body's normal processes. This can cause a deficiency in essential nutrients or interference with the function of the nutrients by altering their absorption, metabolism, utilization, and elimination.

Commonly Prescribed Medications that Interfere with Nutrients

Types of drugs commonly used in dogs that can interfere with nutrition include:

Anticonvulsants used to prevent seizures are often prescribed long-term for dogs with epilepsy. Nutrients depleted from these medications include:

Minerals: calcium, copper, selenium, zinc, magnesium, 

Vitamins B1, B6, B7, B9, B12, A, D, E, and K

Antidepressants are used for behavior modification in dogs. SSRIs (Selective Serotonin Uptake Inhibitors) deplete melatonin and iodine.

Antifungal treatments are used to treat fungal infections. Antifungal medications include Ketoconazole, Itraconazole, and Fluconazole. These medications can cause calcium, magnesium, potassium, and sodium depletion.

Antihistamines are used to treat dogs’ allergies. Diphenhydramine (Benadryl), Cetirizine (Zyrtec), Loratadine (Claritin), and Clemastine (Tavist-1, Antihist-1) can all be purchased over the counter, while Hydroxyzinep requires a prescription. The nutrient affected the most by an antihistamine is Omega-3 fatty acids. Studies have shown that providing Omega-3 in conjunction with antihistamines has a synergistic effect on dogs with atopic dermatitis.

Anti-inflammatories and analgesics are used for inflammation and pain. These are corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDS).

Corticosteroids include prednisone, prednisolone, dexamethasone, triamcinolone, and methylprednisolone. Corticosteroids interfere with the activity of vitamins A, B6, B9, B12, C, D, and K and several minerals including calcium, potassium, magnesium, selenium, zinc, and chromium 

NSAIDS used in dogs include carprofen (Novox or Rimadyl), deracoxib (Deramaxx), firocoxib (Previcox), meloxicam (Metacam ), and grapipant (Galliprant).. NSAIDS can cause a depletion of folic acid and melatonin.	

Antibiotics are used for infections. A great variety of antibiotics are available, each with specific side effects. Antibiotics commonly used for dogs include penicillin (Claxamox), tetracycline (Doxycycline), Neomycin, and trimethoprim sulfa (Ditrim).

Antibiotics, in general, destroy the "good" bacteria (probiotics) in the gastrointestinal tract, causing deficiencies in these nutrients:

Vitamins: Vitamin B1, B2, B3, B5, B6, B7, B12, C and K.

Minerals: Magnesium, calcium, zinc, iron, selenium, iodine, potassium, 

Methotrexate is an antagonist to vitamin B9, interfering with the body's ability to use it. 

Diuretics such as Furosemide are used to reduce water retention.

Diuretics can reduce potassium, magnesium, calcium, sodium, zinc, and vitamins B1, B6, and C.

Propranolol is a beta-blocker used to control dogs' heart rate with irregular heart rhythms and reduce blood pressure. However, it can cause both dangerous increases and decreases in serum potassium levels and spikes in magnesium. All of these alterations can create serious heart complications.

Vitamin and Mineral Supplements can create imbalances in other nutrients. 

There are interactions between all minerals and vitamins utilized in your dog's body. 

A few examples of vitamin interaction include Vitamin B6 is essential for the absorption of vitamin B12; Vitamin B9 is required for the absorption of B1, high levels of Vitamin B6 interfere with B3, and Increased levels of vitamin E may interfere with the absorption or metabolism of vitamin A and  K.

An example of mineral interactions is with skin disorders due to mineral imbalances and deficiencies of copper and zinc. Both are needed at adequate levels for healthy skin.

Supplements must be given with caution and monitored through blood tests, gut microbiome testing, and fur and hair analysis. 

Other Pharmaceuticals that Interfere with Nutrients

During an annual routine wellness examination, your veterinarian will likely recommend a series of vaccinations and flea, tick, and heartworm prevention. Intestinal parasite control may also be encouraged. They all sound like great ideas, except at what cost to your dog's body? 

Vaccinations for distemper, hepatitis, leptospirosis, parainfluenza, parvovirus, and coronavirus are all packed into one injection. The veterinary staff will also advise you to vaccinate your dog against rabies (mandated in most states), Lyme disease, and kennel cough. These are often all done in the same visit.

Your decision to vaccinate your dog should be based on the prevalence of the disease in your area. For example, in Connecticut, Lyme disease (LD), a tick-borne disease, was first characterized in 1975. Cases of LD are found in most continental United States, with the highest prevalence in the Northeastern states and Minnesota and Wisconsin.  

If you reside or plan to visit these states with your dog, the prevention of LD may override the risk of the vaccine side effects. 

The need for vaccination for Bordetella, more commonly known as kennel cough, can also be assessed based on risk. Although kennel cough is highly contagious if your dog is in direct contact with other dogs, it is not usually life-threatening for healthy dogs. 

If your dog rarely encounters other dogs except on the occasional walk, her risk of getting kennel cough is low. This may be a vaccine that you forego unless you plan to board your dog in a kennel or send her to doggie daycare.

Vaccines are such a bombardment to your dog's immune system! As for nutrients affected, vitamin C can be depleted from vaccines. Any dog deficient in vitamin C, vitamin D, vitamin A,  zinc, magnesium, or selenium should not receive any vaccines. For vaccines to be effective, your dog's immune system must be able to mount a response, which is why only healthy dogs should be vaccinated.  

An alternative to vaccinations is titering or antibody testing for these diseases. You can skip those vaccines if your dog's antibody levels are still adequate. Not many veterinarians suggest titer testing. We can assume it is either unaware of its availability or not fully informed of the side effects of vaccines.  

One of the primary ingredients of heartworm preventatives is ivermectin, a macrolide antibiotic. Ivermectin has many known side effects, including depleting vitamins B1, B2, B3, B6, B7, B9, B12, and K.

Weighing the Benefit Against the Potential Harm

Any medication given to your dog can disrupt her metabolism, so you and your veterinarian must weigh the benefits against the potential harm. Unfortunately, not all veterinarians are well-versed in side effects and drug interactions, so educating yourself and advocating for your dog is up to you.

If the side effects are so severe that your dog may suffer more with the drug than without, you should decline the prescription. However, there are many circumstances where you will consider the risks acceptable if there is no alternative therapy or the disease is severe. 

Diabetes is a prime example of a disease that requires a prescription drug, insulin. However, there are also nutritional regimes that may eventually counter the need for insulin. Don't stop educating yourself on a disease just because the veterinarian has a drug that will help your dog. 

By understanding the potential side effects, you can devise a plan to combat them. Find out what nutrients will be affected so you can provide additional foods to counteract the effect. For example, give your dog prebiotics and probiotics whenever she is prescribed antibiotics. 

Try to find alternative non-drug treatments that will have the same or a similar outcome. There are natural alternatives to flea, tick, and heartworm preventatives without the potential adverse side effects.

All medications and vaccines will cause some type of disruption to your dog's ability to maintain balance within her body naturally. The absorption of nutrients is commonly affected.  

As a dog parent, educate yourself on the pros and cons of giving medications to your dog. Do a cost-benefit analysis.

There are times when drugs cannot be avoided. In these circumstances, know the potential nutritional imbalances that can occur so that you can supplement your dog's diet to compensate for possible dietary deficiencies. 

Focus: Nutrition and Food Science: Importance of Nutrients and Nutrient Metabolism on Human Health 

Preventing Pharmaceutical-Induced Nutritional Deficiencies  

Common Nutrient Depletions Caused by Pharmaceuticals | Alternative and Complementary Therapies  

Adherence to risk management guidelines for drugs which cause vitamin | DHPS  

Effect of Oral Administration of Metronidazole or Prednisolone on Fecal Microbiota in Dogs  

https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutrition-in-disease-management-in-small-animals  

Drugs producing vitamin deficiencies - PubMed (nih.gov) 

Statement on Lyme Disease in Dogs: Diagnosis, Treatment, and Prevention - Littman - 2006 - Journal of Veterinary Internal Medicine - Wiley Online Library 

Nutritional Imbalances Caused by Pharmaceuticals

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