The Lymphoid System

The Lymph Nodes In dogs, the primordial structure of the largest lymph nodes is present at 35 to 38 days of gestation, and lymphocytic colonization of the nodes is prominent at 52 to 53 days of gestation (). At birth, puppies and kittens have readily recognizable lymph nodes with a loose reticular structure, low lymphocyte density, and limited organization into cortex and medulla that rapidly proliferates into cortical nodules and medullary cords. Lymph nodes and lymphatic vessels vary in location and number, but their primary function is to participate in immunologic reactions by filtering lymph and recirculating the lymphocytes (). Antigens that gain access to particular body tissues are ultimately found in lymphatic vessels that drain these tissues, making it logical that elements of the immune system are strategically positioned along lymphatic vessels. Although lymph node architecture is relatively uniform throughout the body, nodes near portals of entry of external antigens (mandibular and mesenteric lymph node areas) are often more reactive than nodes in other locations. Lymph Node Disorders As a major site of immunologic recognition, lymph nodes are expected to respond to various local and systemic inflammatory, Read more […]

Thioguanine: 40 mg Tablets

Thioguanine ANTINEOPLASTIC Highlights of Prescribing Information Oral purine analog antineoplastic that may be useful as adjunctive treatment for acute lymphocytic or granulocytic leukemia in dogs or cats Contraindications: Hypersensitivity to thioguanine Caution: Hepatic dysfunction, bone marrow depression, infection, renal function impairment (adjust dosage), or history of urate urinary stones Potentially mutagenic & teratogenic; use milk replacer if nursing Adverse Effects: GI effects, bone marrow suppression, hepatotoxicity, pancreatitis, GI (including oral) ulceration, & dermatologic reactions Cats may be more susceptible than dogs to adverse effects Low therapeutic index; monitoring mandatory What Is Drug Used For? Thioguanine may be useful as adjunctive therapy for acute lymphocytic or granulocytic leukemia in dogs or cats. Pharmacology / Actions Intracellularly, thioguanine is converted to ribonucleotides that cause the synthesis and utilization of purine nucleotides to be blocked. The drug’s cytotoxic effects are believed to occur when these substituted nucleotides are inserted into RNA and DNA. Thioguanine has limited immunosuppressive activity. Extensive cross-resistance Read more […]

Thiotepa Lyophilized Powder for Injection: 15 mg & 30 mg in vials

Thiotepa ANTINEOPLASTIC Highlights of Prescribing Information Antineoplastic used systemically for carcinomas, intracavitary for neoplastic effusions, & intravesical for transitional carcinomas; rarely used in small animal oncology Contraindications: Hypersensitivity to thiotepa; Caution: Hepatic dysfunction, bone marrow depression, infection, tumor cell infiltration of bone marrow, renal dysfunction, or history of urate urinary stones Adverse Effects: Leukopenia most likely adverse effect; other hematopoietic toxicity (thrombocytopenia, anemia, pancytopenia), GI toxicity possible. Intracavitary or intravesical instillation can also cause hematologic toxicity. Potentially teratogenic; use milk replacer if patient nursing Monitor diligently What Is Drug Used For? Veterinary indications for thiotepa include: systemic use for adjunctive therapy against carcinomas, and intracavitary use for neoplastic effusions. In dogs with transitional cell bladder carcinoma, intravesical instillation of thiotepa had significantly less efficacy (mean survival time = 57 days) when compared to a systemic doxorubicin/ cyclophosphamide protocol (mean survival time = 259 days). Pharmacology / Actions Thiotepa is an Read more […]

Thiola (Tiopronin): 100 mg Tablets

Tiopronin (Thiola) 2-MPG ANTIUROLITHIC (CYSTINE) AGENT Highlights of Prescribing Information Drug for prevention (& treatment) of cystine urolithiasis Cautions: Agranulocytosis, aplastic anemia, thrombocytopenia or other significant hematologic abnormality, impaired renal or hepatic function, or sensitivity to either tiopronin or penicillamine Adverse Effects: Coombs’-positive regenerative sphero-cyte anemia, aggressiveness, proteinuria, thrombocytopenia, elevations in liver enzymes, dermatologic effects, & myopathy What Is Drug Used For? Tiopronin is indicated for the prevention of cystine urolithiasis in patients where dietary therapy combined with urinary alkalinization is not completely effective. It may also be useful in combination with urine alkalinization to dissolve stones. Pharmacology / Actions Tiopronin is considered an antiurolithic agent. It undergoes thioldisulfide exchange with cystine (cysteine-cysteine disulfide) to form tiopronin-cystine disulfide. This complex is more water-soluble and is readily excreted thereby preventing cystine calculi from forming. Pharmacokinetics Tiopronin has a rapid onset of action and in humans, up to 48% of a dose is found in the urine within Read more […]

Tonocard (Tocainide HCL): 400 mg, 600 mg Tablets

Tocainide HCL (Tonocard) ORAL ANTIARRHYTHMIC Highlights of Prescribing Information Oral antiarrhythmic with similar activity as lidocaine; not commonly used in veterinary medicine Contraindications: Hypersensitivity reactions to it or amide-type local anesthetics, 2nd or 3rd degree AV block & not being artificially paced. Caution: Heart failure, hematologic abnormalities, or preexisting bone marrow failure. Adverse Effects: CNS effects (depression, ataxia, muscle tremors, etc.), nausea & vomiting (usually transient), cardiovascular effects (hypotension, bradycardia, tachycardia, other arrhythmias, & exacerbation of CHF) Case reports of dogs on long-term therapy (>3 mos.) developing ocular & renal toxicity What Is Drug Used For? Veterinary experience with tocainide is limited. At this time, dogs are the only veterinary species where enough clinical experience has been garnered to recommend its use. It is indicated for the oral therapy of ventricular arrhythmias, principally ventricular tachycardia and ventricular premature complexes. In humans, response to lidocaine can usually predict whether tocainide might be effective. Pharmacology / Actions Tocainide is considered a class IB Read more […]

Demadex (Torsemide): 5 mg, 10 mg, 20 mg, & 100 mg Tablets

TORSEMIDE (Demadex, Torasemide) LOOP DIURETIC Highlights of Prescribing Information Potent loop diuretic potentially useful for adjunctive treatment of CHF in dogs & cats; very little information available on clinical use in veterinary medicine Approximately 10X more potent, longer diuretic action, & more potassium-sparing (in dogs) than furosemide May be more expensive than furosemide, but tablets are now available generically What Is Drug Used For? Torsemide is a loop diuretic similar to furosemide, but it is more potent, its diuretic effects persist for a longer period, and it does not cause as much potassium excretion (in dogs). While clinical use in dogs and cats thus far has been minimal, it potentially may be a useful adjunctive treatment for congestive heart failure in dogs and cats, particularly in patients that have become refractory to furosemide. Pharmacology / Actions Torsemide, like furosemide inhibits sodium and chloride reabsorption in the ascending loop of Henle via interference with the chloride-binding site of the lNa+, 1K+, 2Cl- cotransport system. Torsemide increases renal excretion of water, sodium, potassium, chloride, calcium, magnesium, hydrogen, ammonium, and bicarbonate. Read more […]

Dental Disease and Care

An oral examination should be performed each time a puppy or kitten is presented. Many pathologic or potentially pathologic conditions can be detected at an early age and corrective measures taken. Introducing the pet owner to the concept of oral home care and regular professional dental prophylaxis are the two most important responsibilities of the veterinarian with regard to dental disease care and prevention. Tooth Morphology There are three types of teeth in the deciduous dentition of puppies and kittens: incisor (I), canine (C), and premolar (P); a fourth type, molar (M), is found in the permanent dentition. Each type is designed to be self-cleaning in the non-crowded scissors occlusion, when the animal eats a natural diet, that is, catches its prey. Each tooth type serves a specific function. Incisor teeth are for grooming and nibbling, canine teeth are for grasping and tearing, premolars are for shearing, and molars are for grinding. The cat, a true carnivore, has no occlusal surface on the mandibular molar. The maxillary molar is small and vestigial in the cat (). Each tooth is covered with enamel, the hardest body substance. The bulk of the tooth is dentin, a living tissue that continues to be deposited Read more […]

The Pancreas

Inflammatory Pancreatic Disease The pancreas is a unique organ possessing both exocrine (digestive) and endocrine (hormonal) functions. Inflammatory pancreatic disease affecting only the exocrine portion is extremely uncommon in young dogs and cats (). Consequently, inflammatory pancreatic disease, that is, acute pancreatitis or relapsing pancreatitis that more commonly affects older dogs and cats, has been rarely identified in dogs and cats younger than 6 months of age. The likely causes of inflammatory pancreatic disease in the young dog and cat are abdominal trauma and infectious agents. Abdominal trauma may induce pancreatitis in dogs that are traumatized by motor vehicles and in cats that have fallen or jumped from high places (high-rise syndrome) (). In addition, abdominal surgery may result in acute pancreatitis due to traumatic injury to the pancreas (spearing the pancreas with a surgical instrument) or excessive manipulation of die pancreas. Infectious agents can occasionally contribute to inflammatory pancreatic disease. Pancreatic necrosis can be found on postmortem examination of an occasional dog afflicted with canine parvovirus infection (). It is not known whether the canine parvovirus is directly Read more […]

Autoimmune Disorders

Pemphigus complex the pemphigus complex comprises a group of rare autoimmune diseases described in dogs and cats the diseases are vesiculobullous ulcerative disorders of the skin and often the mucous membranes autoantibody is directed against the epidermal intercellular cement substance and may be demonstrated by direct immunofluorescence testing histologically the pemphigus complex is characterized by acan-tholysis (loss of cohesion between individual epidermal cells) Pemphigus foliaceus the most common of the autoimmune diseases dogs and cats no age, breed or sex predisposition Clinical features often begins on the face, nose and ears as a vesiculobullous or exfoliative pustular dermatitis () footpads are frequently involved with hyperkeratosis mucocutaneous lesions are uncommon Diagnosis history physical examination histological examination: subcorneal acantholysis leading to the development of a cleft. Within the cleft there are neutrophils and eosinophils direct immunofluorescence may reveal intercellular deposition of immunoglobulin throughout the epidermis Differential diagnosis bacterial folliculitis dermatophyte infection seborrhoea systemic lupus erythematosus discoid Read more […]

Dyrenium (Triamterene): 50 mg, 100 mg Capsules

TRIAMTERENE (Dyrenium) POTASSIUM-SPARING DIURETIC Highlights of Prescribing Information Potassium-sparing diuretic that may be considered as an alternative to spironolactone for treating CHF in dogs; limited clinical experience with this drug in dogs/cats Contraindications: Anuria, severe or progressive renal disease, severe hepatic disease, hypersensitivity to triamterene, preexisting hyperkalemia, concurrent therapy with another potassium-sparing agent (spironolactone, amiloride) or potassium supplementation Hyperkalemia possible; must monitor serum K+ What Is Drug Used For? Triamterene is a potassium-sparing diuretic that potentially could be used as an alternative to spironolactone for the adjunctive treatment of congestive heart failure in dogs, however, there is little experience associated with its use in dogs or cats. Pharmacology / Actions By exerting a direct effect on the distal renal tubule, triamterene inhibits the reabsorption of sodium in exchange for hydrogen and potassium ions. Unlike spironolactone, it does not competitively inhibit aldosterone. Triamterene increases excretion of sodium, calcium, magnesium and bicarbonate; urinary pH may be slightly increased. Serum concentrations Read more […]