Diazepam is the veterinary formulation of Valium, a benzodiazepine tranquilliser and central nervous system depressant. It acts directly on the brain and is used clinically for dogs as a sedative, a muscle relaxant and an anticonvulsant. In her article, "Diazepam for Veterinary Use," veterinarian Barbara Forney explains that diazepam is used in dogs to reduce anxiety and to treat behavioural problems, such as "separation anxiety, fear of loud noises or thunderstorms, territorial or social aggression between animals, urine marking or spraying and hair loss due to excessive licking or grooming."
Physical Side Effects
Because diazepam is a muscle relaxant, common side effects of diazepam include weakness, loss of coordination and clumsiness. Some dogs may also experience increased appetite.
Gastrointestinal Side Effects
Some dogs will experience vomiting, loss of appetite or diarrhoea while taking diazepam.
Side Effects Related to Addiction and Withdrawal
Long-term treatment can lead to dependence that could bring undesirable behaviour changes once the drug is discontinued. Because diazepam may be addictive, dogs should be eased off diazepam gradually or they may experience serious withdrawal symptoms. According to Sharon Crowell-Davis, DVM, sudden termination of diazepam can result in "rebound, the resumption of symptoms more intense than prior to treatment. When discontinuing, the common rule of thumb is to decrease the dose no faster than 25 per cent each week."
Side Effects Related to Pregnancy and Lactation
Diazepam crosses the placenta and is present in mother's milk, so it should be avoided in pregnant or lactating dogs and used only when benefits outweigh risks. In humans, it has been shown to be teratogenic during the first trimester of pregnancy, so it may cause birth defects.
Side Efects Related to Drug Interaction
Diazepam is a central nervous system depressant that should not be given in combination with other tranquillisers, narcotics, barbiturates, antihistamines and antidepressants. The effects of digoxin may be increased in patients taking diazepam and patients should be monitored for signs of toxicity. Antacids delay the absorption of diazepam, but this can be easily managed by separating the medications by at least two hours. Doctors Foster and Smith suggest dog owners consult their veterinarian "before using diazepam with vitamins and supplements ... and other drugs since interactions may occur."
Overdose Side Effects
An overdose of diazepam may produce significant central nervous system depression. If you see signs of increased sedation, difficulty breathing, loss of coordination or stumbling, disorientation, depression, decreased reflexes or coma, contact your veterinarian immediately.
Side Serious Side Effects Related to or Causing Other Conditions
Use diazepam with extreme caution in dogs that have liver or kidney disease, have narrow angle glaucoma, are dehydrated or anaemic, have difficulty breathing or are geriatric or obese. Contact your veterinarian if your pet experiences jaundice, pale gums, low platelets or an increased tendency to bruise or bleed while being treated with diazepam.
Allergic Reaction as Side Effect
Contact your veterinarian or an emergency vet clinic immediately if your pet experiences an allergic reaction to diazepam. Symptoms may include facial swelling, hives, itchiness and scratching, diarrhoea, vomiting, shock, seizures, pale gums, cold limbs or unconsciousness.
Mental Status and Behavioral Side Effects
Some dogs may exhibit behaviour such as excitement or aggression after being given diazepam, even when the drug is being used to calm aggressive tendencies. While the drug may help with fear-induced aggression, it must be used with caution because in rare cases, learnt inhibition of aggressive behaviour may be lost. Diazepam can cause sedation and disorientation and should be used with caution in working animals, such as military, police and service dogs. Dogs taking diazepam may exhibit increased friendliness, anxiety, hallucinations, insomnia, amnesia, difficulty learning, depression or lethargy. Some dogs become disoriented and may wander around the house whining.