PHARMACODYNAMICS

PHARMACODYAMICS

• Pharmacodynamics is the study of how drugs produce effects on living individuals. Drug is said to have an effect if perceptible changes in a biologic system can be obtained.

DRUG ACTIVITY

•  A measure of the physiological response that a drug produces. A less active drug produces less response, and a more active drug produces more response.

• It is the Ability of the drug to combine with components of the cell membrane or with internal components of the cell to cause alteration in cell function.

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BASED ON THE DRUG BROUGHT IN THE LAB, WHAT IS THE EFFECT OF THE DRUG?

• Mefenamic acid is a non-steroidal anti-inflammatory drug used to treat pain including menstrual pain.

EXPLAIN THE MECHANISM OF ACTION OF THE ABOVE DRUG.

• Mefenamic acid is a competitive inhibitor of COX-1 and COX-2, which are responsible for the first committed step in prostaglandin biosynthesis. Decreasing the activity of these enzymes thus reduces the production of prostaglandins, which are implicated in inflammation and pain processes.

HOW CAN THE DRUG ACTION BE IDENTIFIED.

• It is important to distinguish between actions of drugs and their effects. Actions of drugs are the biochemical physiological mechanisms by which the chemical produces a response in living organisms. The effect is the observable consequence of a drug action.

HOW CAN THE DRUG ACTION BE IDENTIFIED.

Types of drug action:

Stimulation

• Stimulating drugs increase the activity of specific cells. (Ex. Caffeine stimulates cortical activity; epinephrine stimulates the effectors cells innervated by adrenergic fiber.). No anatomic lesions are produced and ordinarily the tissue recovers function after sufficient rest.

Depression

• Drug depression decreases the activity of specialized cells. (Ex. Barbiturate depress the central nervous system, Codeine depresses the cough center in the medulla). The diminished function, characteristic of the action of depressive drugs, is ordinarily a reversible process as the effective dose is metabolized

HOW CAN THE DRUG ACTION BE IDENTIFIED.

Irritation

• Drug Irritation refers to the action of drug on the nourishment, growth, and morphology of the cell. Varying degrees of irritation may be induced in all kinds of tissue. Mild irritation may be used to stimulate activity of tissue. Excessive doses sometimes result in intestinal bleeding, which is evidence of the irritating action of the drug.

Chemotherapy

• Chemotherapeutic drugs are administered to attenuate or kill pathogenic organisms without toxicity to the host. These drugs possess specific toxicity for the invading pathogen.

Jones Meyer J. Veterinary Pharmacology and Therapeutics, 1957

 

 

GIVE EXAMPLE OF HOW DRUGS HAVE BEEN DISCOVERED

ASPIRIN

• Hippocrates was left historical records of pain relief treatments, including the use of powder made from the bark and leaves of the willow tree to help heal headaches, pains and fevers.

• 1829, scientists discovered that it was the compound called salicin in willow plants which gave you the pain relief.

GIVE EXAMPLE OF HOW DRUGS HAVE BEEN DISCOVERED

ASPIRIN

• Henri Leroux had extracted salicin, in crystalline form for the first time, and Raffaele Piria succeeded in obtaining the salicylic acid in its pure state.

• The problem was that salicylic acid was tough on stomachs and a means of 'buffering' the compound was searched for.

GIVE EXAMPLE OF HOW DRUGS HAVE BEEN DISCOVERED

ASPIRIN

• 1853, Gerhardt neutralized salicylic acid by buffering it with sodium (sodium salicylate) and acetyl chloride, creating acetylsalicylic acid. Gerhardt's product worked but he had no desire to market it and abandoned his discovery.

• 1899, a German chemist named Felix Hoffmann, who worked for a German company called Bayer, rediscovered Gerhardt's formula. Felix Hoffmann made some of the formula and gave it to his father who was suffering from the pain of arthritis.

GIVE EXAMPLE OF HOW DRUGS HAVE BEEN DISCOVERED

ASPIRIN

• The folks at Bayer came up with the name Aspirin, it comes from the 'A" in acetyl chloride, the "spir" in Spiraea ulmaria (the plant they derived the salicylic acid from) and the 'in' was a then familiar name ending for medicines.

DISCOVERIES OF NEW VETERINARY DRUGS

PALLADIUM• Palladia (toceranib phosphate) was the first

FDA-approved antiangiogenic and antiproliferative cancer treatment specifically for dogs.

• Manufactured by Pfizer and was released for use by veterinary oncologists in 2009 for the treatment of Patnaik grade II or III, recurrent cutaneous mast cell tumors with or without regional lymph node involvement in dogs.

• It has been a remarkable adjunct for the treatment of canine mast cell tumors (MCT)

DISCOVERIES OF NEW VETERINARY DRUGS

PALLADIUM• Palladia is a receptor tyrosine kinase

(RTK) inhibitor. Inhibition of RTKs on endothelial cells, pericytes, and tumor cells disrupts multiple processes necessary for tumor growth.

MECHANISM OF ACTION OF ANY DRUGS UNDER VPHAR200

PHENOBARBITAL

• Phenobarbital acts on GABAA receptors, increasing synaptic inhibition. This has the effect of elevating seizure threshold and reducing the spread of seizure activity from a seizure focus. Phenobarbital may also inhibit calcium channels, resulting in a decrease in excitatory transmitter release. The sedative-hypnotic effects of phenobarbital are likely the result of its effect on the polysynaptic midbrain reticular formation, which controls CNS arousal.

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