Trimeprazine with Prednisolone
**Trimeprazine with Prednisolone** (commonly known by the brand name Temaril-P®) is a combination medication widely used in veterinary medicine primarily to manage pruritus (itching) and coughing in dogs. * **Trimeprazine** (also known as alimemazine) is a phenothiazine derivative that acts as a potent antihistamine, mild sedative, and antitussive. * **Prednisolone** is an intermediate-acting glucocorticoid that provides robust anti-inflammatory and immunosuppressive effects. > **Clinical Pearl:** The synergistic effect of combining an antihistamine with a corticosteroid allows for a lower dose of prednisolone to achieve the same antipruritic effect. This "steroid-sparing" approach helps minimize the risk of long-term glucocorticoid-induced adverse effects while effectively controlling clinical signs.
Mechanism: The drug exerts its effects through two distinct mechanisms: * **Trimeprazine**: Acts primarily as a competitive antagonist at **H1-histamine receptors**, preventing histamine-induced capillary permeability, vasodilation, and pruritus. It also exhibits central antitussive and sedative properties by antagonizing central **dopamine (D2)** and **muscarinic (M1)** receptors in the brainstem and reticular activating system. * **Prednisolone**: Diffuses across cell membranes and binds to **cytosolic glucocorticoid receptors**. The receptor-ligand complex translocates to the nucleus → alters gene transcription → induces production of lipocortin-1 (annexin-1) → inhibits **phospholipase A2**. This blocks the release of arachidonic acid, thereby suppressing the synthesis of key inflammatory mediators, including **prostaglandins** and **leukotrienes**.
Dosing by species
- Antipruritic and antitussive therapy · Weight up to 10 lb = 1/2 tab PO twice daily; 11-20 lb = 1 tablet twice daily; 21-40 lb = 2 tablets twice daily; over 40 lb = 3 tablets twice daily. After 4 days reduce dose to 1/2 of initial dose or to an amount just sufficient to maintain remission of symptoms; adjust as necessary. · PO · twice daily · After 4 days reduce dose
- Treatment of pruritus · 1 tablet per 10 kg of body weight once daily for 3-5 days, then every other day. · PO · once daily then every other day · 3-5 days then every other day · Giving with an EFA (essential fatty acid) may reduce the dose and frequency, if not the need for, glucocorticoids.
- Atopic dermatitis · 1 tablet of Temaril-P per 5 kg body weight q12h for one week, then once daily for one week, then q48h (every other day). · PO · q12h then once daily then q48h · 1 week q12h, 1 week once daily, then q48h
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Systemic fungal infections
- Hypovolemia or shock
- Tetanus or strychnine intoxication
- Late pregnancy (last trimester) due to risk of inducing parturition
Adverse effects
- Sedation
- Depression
- Hypotension
- Extrapyramidal reactions (rigidity, tremors, weakness, restlessness)
- Polyuria (increased urination)
- Polydipsia (increased thirst)
- Polyphagia (increased appetite)
- Elevated liver enzymes
- Weight loss or weight gain
- Vomiting
- Diarrhea
- Iatrogenic hyperadrenocorticism (Cushing's syndrome) with chronic use
- Delayed wound healing
- Osteoporosis
- Increased susceptibility to infections
Drug interactions
- ACE Inhibitors · Phenothiazines may increase hypotensive effects
- Amphotericin B · Concomitant use with glucocorticoids may cause severe hypokalemia
- Antacids · May cause reduced GI absorption of oral phenothiazines
- Antidiarrheal mixtures (Kaolin/pectin, bismuth) · May cause reduced GI absorption of oral phenothiazines
- Anticholinesterase agents (pyridostigmine, neostigmine) · In myasthenia gravis patients, concomitant use may lead to profound muscle weakness
- Aspirin (salicylates) · Glucocorticoids may reduce salicylate blood levels
- Cisapride · Increased risk for cardiac arrhythmias when used with phenothiazines
- CNS Depressants (barbiturates, narcotics, anesthetics) · May cause additive CNS depression
- Cyclophosphamide · Glucocorticoids may inhibit hepatic metabolism of cyclophosphamide
- Cyclosporine · May mutually inhibit hepatic metabolism, increasing blood levels of both drugs
- Digoxin · Increased risk for arrhythmias secondary to glucocorticoid-induced hypokalemia
- Diuretics, potassium-depleting (furosemide, thiazides) · Concomitant use with glucocorticoids may cause hypokalemia
Monitoring
- Efficacy (reduction in pruritus or coughing)
- Degree of sedation
- Anticholinergic effects
- Adverse effects associated with corticosteroids (e.g., PU/PD, weight changes, liver enzyme elevations)
Overdose
Acute overdosage should be handled similarly to phenothiazine (e.g., acepromazine) toxicity. Overdose may cause profound sedation, depression, hypotension, and extrapyramidal signs (tremors, rigidity). Treatment is largely supportive and symptomatic. Do not use epinephrine for hypotension as it may cause further vasodilation (epinephrine reversal); use norepinephrine or phenylephrine if pressors are required.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.