First hour reactions in a 7 kg dog
For a dog your size, 25 mg of sertraline is enough to trigger symptoms rapidly—often within 30-60 minutes. The drug hits the bloodstream quickly, especially if eaten on an empty stomach. Right now, you might see dilated pupils or excessive yawning as early neurological effects. Salivation or lip-licking can precede vomiting.
Prevent access to stairs or furniture—wobbly legs make falls likely. If he tries to drink water, offer ice chips instead to reduce nausea risk. His gums should stay pink; press them briefly to check that color returns within 2 seconds. Any delay could mean circulation issues starting.
Why small dogs show stronger reactions
At 7 kg, your dog's body can't dilute the medication like a larger animal could. Serotonin syndrome symptoms—agitation, tremors, high heart rate—tend to be more severe in petite breeds. Even if he seems calm now, don't assume safety; symptoms often come in waves over several hours.
Count his resting breaths per minute (normal is 10-30) and feel his heartbeat behind the left elbow. A rate over 140 beats per minute needs urgent care. Small dogs dehydrate faster from vomiting or panting, so watch for sticky gums or skin that tents when gently pinched.
The danger window: 2-6 hours post-ingestion
This is when serotonin levels peak in the brain, causing the most severe signs. Tremors often start in the face or front legs before spreading. Your dog might seem "drunk"—circling, stumbling, or unable to sit still. These aren't just discomfort; they signal neurological distress.
Keep lights dim and noise minimal—overstimulation worsens symptoms. If he starts panting when it's not hot, or his body feels unusually warm to the touch, serotonin syndrome is affecting temperature regulation. Don't cool him with water unless directed—sudden temperature drops can shock his system.
What emergency vets will ask when you arrive
Time the duration of any tremors or seizures (write it down). Note whether he's responsive to his name during episodes. Vets will want to know if he's urinated normally—retention can occur. Bring the pill bottle or remaining tablets to confirm dosage.
Prepare to describe his normal activity level for comparison. A usually energetic dog who won't stand is more concerning than a calm breed showing the same behavior. If he's had any past reactions to medications, even unrelated ones, mention those—some dogs are prone to stronger drug sensitivities.
The step-by-step response, from the first minute to the vet visit, is in our Human Stress and Anxiety Medication Poisoning in Dogs and Cats emergency guide.