MIDTERM II - TOPIC 26-28 Flashcards
26: ANTIHISTAMINES: 27-28: PHARMACOLOGY OF THE RESPIRATORY TRACT:
26: ANTIHISTAMINES:
- Used for? Efficacy?
- In severe histamine release, what reaction do we see?
- Example when we see this reaction
- Severity of the reaction?
- Treatment for this reaction?
- What happens during the reaction?
- Antihistamines combined whit?
- These are the oldest drugs used as an anti-allergic however, their efficacy is not that high.
- In severe histamine release where we can see anaphylactic reactions and anaphylactic shock for example in
- vaccines,
- penicillins,
- insect bites or even
- when we administer LOKIVETMAB to a cat or horse etc.
- Anaphylactic reactions can be life-threatening and in these cases, antihistamines can be used as a treatment but they must be combined with other, more effective, drugs.
- In anaphylactic reactions, vascular permeability increases i.e. epiglottis oedema can occur, leading to suffocation.
- Angioedema (tumors and nodules on the head) can occur like in the picture below of the dog.
- This can be followed by a vaccination reaction.
- In extreme cases, severe vasodilation can lead to shock i.e. anaphylaxis can be life-threatening in which we treat it with antihistamines combined with
- adrenaline,
- glucocorticoids etc.
26: ANTIHISTAMINES:
- Other allergy mediated diseases?
- Antihistamines and efficacy, how many % active in the dog?
- Due to atopic dermatitis, it is mediated by histamine and?
- Safety and economic point of view
-
Allergy mediated diseases e.g.
- atopic dermatitis,
- cutaneous food adverse reactions (food allergy) or
- flea allergy dermatitis (FAD),
- antihistamines have a low efficacy where they are active in only 20% of the dog.
- This is due to the fact that the majority of cases of atopic dermatitis are not only mediated by histamine but by other cytokines e.g. interleukins etc.
- They are safe and cheap and this is why they are tried.
26: ANTIHISTAMINES:
- When can we use antihistamines prior to?
- Which substance?
- Before the administration of which drug (causes serious histamin release)
- Used before surgery as
- ACEPROMAZINE e.g.
- before morphine administration as we have learned that morphine causes a serious histamine release.
26: ANTIHISTAMINES:
Mechanism of action:
- Acts like which inhibitors?
- Not …..?
- Do not bind to which receptor to block histamine binding
- Known as??
- Histamine receptor has 2 stages?
- If histamin is present - Which reaction?
- Side effects
- In case of drug administration what will favor which reaction? What will happen due to it?
Mechanism of action:
- These, like JAK inhibitors,
- are not antagonists i.e.
- they do not bind to the histamine receptor to block histamine binding.
- Instead, they are known as inverse agonists.
- The histamine receptor has an active state (GTP present) and an inactive state (GDP present) that are within a unique balance with each other.
- If histamine is present e.g. in an anaphylactic reaction, the active state will be initiated and side effects of
- vasodilation,
- epiglottis oedema,
- nodules etc. can be seen.
- In the case of drug administration, these inverse agonists (antihistamines) will favor the left reaction and inactive the action and the side effects will be inhibited.
26: ANTIHISTAMINES:
Usage:
Usage:
- These are used in allergic reactions of course.
- In asthma or RAO,
- their use is controversial where their activity is not high enough and they usually do not work.
- They are used in anaphylactic reactions in combination with
- adrenaline and
- glucocorticoids (antihistamines will not be enough).
- In the case of atopic dermatitis etc. the chance of success with antihistamines is approx. 20-25%.
26: ANTIHISTAMINES
Other classes of drugs used:
- These drugs have a very unique place in the veterinary field.
- They are put into two generations.
-
Ist generation: These cross the blood-brain barrier very easily, this is why their side effects include
- sedation,
- uncoordinated movement,
- sleepiness,
- ataxia etc. i.e. CNS side effects
- 2nd generation: These drugs do NOT cross the blood-brain barrier as well and this is why they cause sedation much less frequently when administered. Most of the human drugs are 2nd generation
26: ANTIHISTAMINES
Other classes of drugs used:
Ist generation:
-
Ethylenediamines:
- CHLOROPYRAMINE,
- CHLORPHENIRAMINE
-
Ethanolamines:
- DIPHENHYDRAMINE,
-
DIMENHYDRINATE.
- These two drugs are frequently used for vaccine allergy i.e. if you expect vaccine allergy, which is primarily seen in small dogs >10 kg.
- This can occur in cases when an owner tells you that when their dog was previously vaccinated, they suffered an allergic reaction.
- They are given orally, half an hour before administering the vaccination.
-
Phenothiazines:
- PROMETHAZINE,
- ACEPROMAZINE
-
Piperazines:
- HYDROXYZINE.
- This drug has the best activity in atopic dermatitis.
- This was used before we had LOKIVETMAB.
- The drug worked however, the action is slower than lokivetmab.
- It is very safe but its efficacy is not as high as lokivetmab.
-
Other:
- DIMETINDEN,
-
CYPROHEPTADINE.
- Used as an appetite stimulant
- Feline asthma.
26: ANTIHISTAMINES
Other classes of drugs used:
Ist generation:
Ethylenediamines:
Ethylenediamines:
- CHLOROPYRAMINE,
- CHLORPHENIRAMINE
26: ANTIHISTAMINES
Other classes of drugs used:
Ist generation:
Ethanolamines:
Ethanolamines:
- DIPHENHYDRAMINE,
- DIMENHYDRINATE.
- These two drugs are frequently used for vaccine allergy i.e.
- if you expect vaccine allergy, which is primarily seen in small dogs >10 kg.
- This can occur in cases when an owner tells you that when their dog was previously vaccinated, they suffered an allergic reaction.
They are given orally, half an hour before administering the vaccination.
26: ANTIHISTAMINES
Other classes of drugs used:
Ist generation:
Phenothiazines:
Phenothiazines:
- PROMETHAZINE,
- ACEPROMAZINE
26: ANTIHISTAMINES
Other classes of drugs used:
Ist generation:
Piperazines:
Piperazines:
-
HYDROXYZINE.
- This drug has the best activity in atopic dermatitis.
- This was used before we had LOKIVETMAB.
- The drug worked however, the action is slower than lokivetmab.
- It is very safe but its efficacy is not as high as lokivetmab.
.
26: ANTIHISTAMINES
Other classes of drugs used:
Ist generation:
Other:
Other:
- DIMETINDEN,
-
CYPROHEPTADINE.
- Cyproheptadine is also used as an appetite stimulant
- Used in cases of feline asthma
26: ANTIHISTAMINES
Other classes of drugs used:
2nd generation:
-
Most of the human drugs are 2nd generation e.g.
- LORATADINE,
- CETIRIZINE,
- LEVOCETIRIZINE,
- CLARITINE.
- These are primarily used in humans however, they can also be used in dogs as trial and error drugs.
- Some can react well while others may not react at all.
26: ANTIHISTAMINES
Pharmacokinetics:
- Absorbtion
- Dirstribution
- Blood brain barrier
- Metablolized
- CYP-450
Pharmacokinetics:
- These drugs have good oral absorption however, it can be
- Slow with the maximum plasma concentration (Cmax)
- being 2-3 hours.
- There is a difference in distribution between the 1st and 2nd generation drugs as they do not cross the blood-brain barrier with the same efficiency.
- This is because the 2nd generation is in an ionized form in the blood which
- hinders its transport through the membranes.
- They are also extensively albumin-bound.
- These two factors reduce the blood-brain barrier penetration.
-
Metabolized in the liver and they are cytochrome (CYP-450) inducers i.e.
- they affect (mainly reduce) other drug’s activity as they
- increase cytochrome enzymes
- which will help their metabolism.
- This is one reason why they are not used.
26: ANTIHISTAMINES
Side effects:
Side effects:
- They are very safe drugs.
- They can cause CNS depression (sedation)
-
Cardiac toxicity
- Primarily associated with 1st generation drugs and in humans
- resulting in a prolonged QT interval in the ECG
- Fortunately, this is not so frequent in animals.
- Primarily associated with 1st generation drugs and in humans
- These drugs can be appetite suppressants (primarily in 1st generation drugs and in humans)
- Exception of CYPROHEPTADINE = Appetite stimulant.
- These are very safe but have low efficacy.
All in all, the best drugs to use would be
- OCLACITINIB,
- LOKIVETMAB or
- CYCLOSPORIN.
26: ANTIHISTAMINES
PHARMACOLOGY OF IMMUNOSUPPRESSION:
- When we apply glucocorticoids in higher doses,
- Immunosuppressive effect.
- Other immunosuppressant agents include
- antimetabolites,
- alkylating agents
- cytokine gene expression inhibitors.
26: ANTIHISTAMINES
Immunosuppression indications:
Immunosuppression indications:
- Autoimmune diseases:
- H**ypersensitivity diseases:
- Transplantation:
26: ANTIHISTAMINES
Immunosuppression indications:
Autoimmune diseases:
Autoimmune diseases:
- These affect the mucous membrane and the skin.
-
LUPUS, pemphigus complex
-
Reaction against keratinocytes i.e.
- Breakdown of intracellular desmosomal bridges
- Release of rounded keratinocytes
-
Reaction against keratinocytes i.e.
- IHA (immune haemolytic anaemia)
- KCS (keratoconjunctivitis sicca) - dry eye disease
26: ANTIHISTAMINES
Immunosuppression indications:
Hypersensitivity diseases:
Hypersensitivity diseases:
- Atopic dermatitis
- Asthma
- IBD (inflammatory bowel diseases)
26: ANTIHISTAMINES
Immunosuppression indications:
Transplantation:
Transplantation:
In order to avoid transplantation, immunosuppressant agents should be applied.
26: ANTIHISTAMINES
Immunosuppression indications:
- What does the picture show
- What to do, 1st step?
- If not enough fluid?
- What should you apply?
- Name the drug(s)?
- KCS with damage to the cornea.
- An ulcer can form in the cornea
-
First stage = Perform the Schirmer test
- Tell you whether or not there is enough tear fluid on the eye.
- If there is not enough, we would suspect the presence of KCS.
- You can apply cholinergic parasympathomimetics to the eye such as
- PILOCARPINE but this is only symptomatic treatment. For better results, you can use
- CYCLOSPORINE or
- PIMECROLIMUS.
Immunosuppression can alleviate KCS.
26: ANTIHISTAMINES
Drugs:
In general + antimetabolites
Drugs:
We can sometimes combine these drugs e.g.
-
CYCLOSPORINE can be combined with PREDNISOLONE which is a glucocorticoid.
* This combination can have a beneficial effect if you would like to treat auto-immune disorders.
Antimetabolites:
- These block enzymes irreversibly
- Inhibit or cause damage to DNA.
- This means that they can be used to treat cancer as well as an antineoplastic agent.
26: ANTIHISTAMINES
Drugs:
- Purine-analogues:
- Pyrimidine-analogues: LEFLUNOMIDE.
- Folic acid antagonists: METHOTREXATE.
- Alkylating agents:
- Glucocorticoids:
- Cytokine gene expression inhibitors:
26: ANTIHISTAMINES
Drugs:
1. Purine-analogues:
- AZATHIOPRINE
- Integrates into? What will it do?
- Used to treat?
- Its antineoplastic has a significant effect on? Causing?
- Sideeffects?
- Prodrug?
- Sensitivity and species?
- Release?
- Administration
- Appication for which disease
- How often administered
- Contraindications
1. Purine-analogues:
- AZATHIOPRINE,
- MYCOPHENOLATE-MOFETIL.
-
Azathioprine is a purine-analog that, once integrated into DNA, will
- interfere with transcription and
- reduces proliferation of the cells i.e.
-
Used to treat
- immune-mediated hemolytic anaemia,
- inflammatory bowel disease,
- lupus etc.
- This antineoplastic will have a significant effect on
- cell division (will block cell division)
-
Block enzymes irreversibly i.e.
- Cause inhibition or DNA damage
-
Several side effects - especially
- vomiting,
- diarrhea (GI disturbances because it has a significant effect on proliferative cells)
- vomero suppression
- Reduction in lymphocyte numbers (lymphocytopenia),
- Anaemia
- Thrombocytopenia.
- Due to this DNA inhibition, it is also used to treat cancer.
- Its prodrug is MERCAPTOPURINE and
- cats are very sensitive to it.
- The release is slow i.e.
- takes up to 2 weeks to start working
- but the effect is prolonged.
- It is applied i/v but orally is also possible.
- The application is for auto-immune diseases.
- It is administered once a day for one week or every second day.
- Please do NOT administer to pregnant or breeding animals as it has irreversible damage to gonads.
26: ANTIHISTAMINES
Drugs:
- Purine-analogues:
2. MYCOPHENOLATE-MOFETIL.
- Mycophenolate-mofetil vs azathioprine?
- Side effects
- Usage in cats
- Mechanism of drug
- Censequence
- Onset of action
- Usage in combinations
- Effect on which organ
- If applied orally
- In which condition is it especially better to use mycophenolate-mofentil instead of azathioprine?
1. Purine-analogues:
- AZATHIOPRINE,
- MYCOPHENOLATE-MOFETIL.
- The second purine-analog is mycophenolate mofetil.
-
We prefer this drug to azathioprine as the
- side effects are much rarer.
- Liver toxicity,
- vomero suppression
- acute pancreatitis is not as significant in comparison.
- side effects are much rarer.
- This drug is also safe to use routinely in cats.
- The mechanism of this drug is that it will inhibit inosine monophosphate dehydrogenase which is necessary to have purine.
- The consequence of this is that there will be a reduction in T and B cell proliferation.
- This is much safer.
- Gastrointestinal side effects are also rare.
- This has a faster onset of action also.
- It is regularly used in combination with steroid and CYCLOSPORINE.
- This drug will have an effect on bone marrow as there is de novo GTP synthesis i.e. salvage pathway.
- Because of this, only the T and B-lymphocytes will be affected.
- GI bone marrow will not be affected by the salvage pathways.
- If this drug is applied orally, it will be hydrolyzed and converted to MYCOPHENOLIC ACID through the activation of plasma esterase i.e.
- If there is a liver insufficiency, this drug is better to use in comparison to azathioprine.
26: ANTIHISTAMINES
Drugs:
2. Pyrimidine-analogues:
2. Pyrimidine-analogues:
LEFLUNOMIDE.
26: ANTIHISTAMINES
Drugs:
3. Folic acid antagonists:
- Blocks?
- Result if we do not have enough tetrahydrofolic acid?
- Administration?
- Stimulates
- Cells in resting phase
- Applied against?
- Side effects
3. Folic acid antagonists: METHOTREXATE.
- Methotrexate will block dihydrofolate reductase.
- The final result of this is that we do not have tetrahydrofolic acid i.e.
- Nucleic acid and DNA synthesis will be blocked.
- It can be applied i/v, orally and i/m.
- It will stimulate the apoptosis of T-cells i.e.
- this specifically influences T-cells.
- It has no effect on the cells in the resting phase.
- It can also be applied against LYMPHOMA in dogs and cats (antineoplastic agent).
- The side effects can be
- hepatotoxicity,
- pulmonary toxicity,
- gastrointestinal side effects
-
Kidney side effects also i.e.
- they are not as safe as mycophenolate mofetil. GI upset can occur.