Chocolate is probably the most common poison we see in general practice: this sounds like an odd statement to make as, of course, it is completely non-toxic in people!
However, dogs metabolise one component of chocolate very differently to us - this part is called theobromine and is found in the cocoa part of chocolate. Because of this, chocolates that are high in cocoa solids, such as very good quality dark chocolate (i.e., 75% cocoa solidsa) are the most dangerous; white chocolate contains almost no theobromine and most milk chocolates also contain very low levels.
Dogs metabolise theobromine very differently to us and, when eaten in large quantities, it can cause some very severe health problems:
- Central nervous system stimulation – in dogs, theobromine can greatly ‘overstimulate’ the brain and other parts of the nervous system. This can lead in less severe cases to excitability, hyperactivity and restlessness, but in more severe cases can cause tremors and convulsions (fits or seizures)
- Heart and circulation – theobromine can cause the heart to beat too fast (tachycardia), an increase in blood pressure and, in severe cases, an abnormal heart beat (arrhythmia)
- Muscle – theobromine can cause changes in the muscle tone of the dog, leading to weakness in less severe cases or even muscle rigidity (stiffness) in the more severely affected patients.
- Occasionally problems with kidney function have been seen.
All of the severe side effects mentioned above are life threatening conditions and need to be treated as emergencies. Fits must be treated with sedative drugs; heart problems need to be carefully monitored, sometimes by ECG, to ensure that they are not compromising the dog’s circulation; kidney problems need to be treated with intravenous fluids.
As mentioned above, different types (and brands) of chocolate contain varying amounts of theobromine. The toxicity of theobromine is determined by how much your dog has eaten in relation to his or her weight. If you are concerned that your dog has eaten chocolate get in touch with us immediately - it is really helpful if you still have the wrapper of the chocolate or can at least tell us what type your dog has eaten. It is also important to know how much chocolate your dog has eaten (an estimate is certainly better than nothing), as we can then work out roughly how many milligrams of theobromine he or she has eaten per kg of bodyweight. This will give us an idea of whether we should be treating for theobromine poisoning or not. As an aside, this is the case in any suspected cases of poisoning - if you can tell us what you think your animal has eaten and roughly how much, it can greatly help us to correctly treat him or her.