toxicosis and it is therefore avoided to control hyperactivity, restlessness, irritability or other excitatory behavioural changes; however, it can be used in the acute management of seizures (Albretsen, 2002; Stern and Schell, 2012). Phenothiazine tranquilizers have been recommended to control hyperactivity, restlessness, irritability or other behavioural changes (Stern and Schell, 2012). Acepromazine can initially be administered at 0.05 mg/kg IV and titrated to effect. The dose can be gradually increased to 0.1 to 1.0 mg/kg if clinical signs do not resolve with lower doses. Alternatively, chlorpromazine can initially be administered at 0.5 mg/kg IV and subsequently titrated up to effect. Blood pressure should be monitored at higher doses of phenothiazine to ensure that hypotension does not occur. Animals should be kept in a dark and quiet area and stimulation should be minimized (Stern and Schell, 2012). Treatment of tachycardia or other cardiac arrhythmias may sometimes be required. Urinary acidification has been recommended (to a pH of between 4.5 and 5.5) to enhance the elimination of amphetamines. This can be achieved with ammonium chloride administration at 100 to 200 mg/kg/day PO divided four times daily or ascorbic acid 20–30 mg/kg PO, SQ, IM or IV. Urinary acidification should not be attempted if the animal is acidotic, if acid-base status cannot be monitored regularly, or in case of rhabdomyolosis or acute renal failure (Albretsen, 2002; Stern and Schell, 2012).
Prognosis
Prognosis is generally good with animals receiving prompt and appropriate treatment (Stern and Schell, 2012).
Selective serotonin reuptake inhibitors
Overview
Selective serotonin reuptake inhibitors (SSRIs) such as sertraline (Zoloft), fluoxetine (Prozac), paroxetine (Paxil), and fluvoxamine (Luvox) are often used to treat depression, obsessive-compulsive disorders and other behavioural problems in people (Albretsen, 2002). Fluoxetine has been used in dogs for the treatment of fear or anxiety, acral lick dermatitis and narcolepsy. Paroxetine has been used to treat urine-spraying problems in cats.
Mechanism of action
As suggested by their name, SSRIs inhibit the reuptake of serotonin at the presynaptic membrane resulting in increased synaptic serotonin levels and overstimulation of serotonin receptors.
Clinical presentation
Clinical signs include obtundation, stupor or coma, anorexia, vomiting, diarrhoea, hyper-salivation, abdominal pain, arrhythmias, hypo- or hypertension, tachypnea, dyspnoea, hyperactivity, hyperaesthesia, tremors, seizures (rarely) and hyperthermia. Signs consistent with CNS depression (e.g. obtundation, stupor or coma) are more common than signs of CNS stimulation (e.g. agitation, aggression, tremors or seizures) (Thomas et al., 2012).
Diagnosis
Diagnosis is based on the history of SSRI ingestion, clinical signs and recovery of pills or capsules in the gastric content from vomitus or lavage fluids.
Management
There are no antidotes available for the treatment of SSRI toxicosis. Treatment is symptomatic and supportive, including induction of emesis (in asymptomatic animals), gastric lavage, activated charcoal with a cathartic (in animals without diarrhoea) (Table 4.1), antiarrythmic agents, skeletal muscle relaxants, AEMs (see Table 4.1 and Chapters 12 and 24) and supportive care. In animals with severe clinical signs, serotonin receptor antagonists such as cyproheptadine at 1.1 mg/ kg PO in dogs and 2.4 mg per cat PO can be administered. The medication can be crushed, mixed with saline and administered rectally to animals unable to take oral medications (Albretsen, 2002).
Prognosis
The overall prognosis for animals with SSRI toxicosis is excellent with prompt and appropriate treatment (Thomas et al., 2012).
5-Hydroxytryptophan
Overview
5-Hydroxytryptophan (5-HTP), sometimes called Griffonia seed extract, is sold as an over-the-counter dietary supplement. It has been used to help with depression, chronic headaches, obesity and insomnia in people.
Mechanism of action
5-HTP is rapidly converted to serotonin within target cells of the CNS and cardiovascular system, resulting in overstimulation of serotonin receptors.
Clinical presentation
Clinical signs occur from 10 min to 4 h after ingestion and include vomiting, diarrhoea, abdominal pain, hypersalivation, mydriasis, seizures, hyperthermia, obtunded mental status, tremors, hyperesthesia, ataxia, tachycardia and tachypnea (Gwaltney-Brant et al., 2000). In a study including 21 dogs with evidence of accidental 5-HTP ingestion, the minimum toxic dose reported was 23.6 mg/kg and the minimum lethal dose was 128 mg/kg (Gwaltney-Brant et al., 2000).
Diagnosis
Diagnosis is based on history of exposure and clinical signs.
Management
Treatment includes decontamination (by induction of emesis and/or gastric lavage, administration of activated charcoal), AEMs (see Table 4.1 and Chapters 12 and 24) and supportive care including intravenous fluid therapy and convective whole body cooling. Cyproheptadine, a serotonin antagonist, has been used at 1.1 mg/kg, PO or rectally, every 1 to 4 h until signs resolve. Rectal administration may be preferred when severe vomiting or recent administration of activated charcoal make the oral route unfeasible (Gwaltney-Brant et al., 2000).
Prognosis
The majority of dogs that receive prompt and aggressive treatment recovered within 36 h after exposure (Gwaltney-Brant et al., 2000).
Guarana ( Paullinia cupana ) and ma huang ( Ephedra sinica )
Overview
Guarana (Paullinia cupana), a natural source of caffeine, and ma huang (Ephedra sinica), a natural source of ephedrine, are the main components of an herbal medicine marketed as a weight loss and energy supplement.
