FARMACOLOGÍA S6-3
New Section
The discussion focuses on differentiating between symptoms of common cold and infections caused by various agents, including bacteria and environmental factors.
Understanding Symptoms and Causes
- The speaker highlights that symptoms like headache, fever, sneezing, and nasal congestion do not always indicate a common cold but can be signs of an infection.
- Various agents such as viruses, occupational substances, and environmental factors can lead to similar symptoms.
- Medications contain multiple active ingredients like Beta or Alpha 1 adrenergic antihistamines and corticosteroids in a single formulation for treating infections.
Antihistamines Classification
This part delves into the classification of antihistamines based on generations and their effects on individuals.
Antihistamine Generations
- Antihistamines are classified into first generation and second generation based on their properties.
- First-generation antihistamines have more side effects like sedation compared to second-generation ones.
Adverse Effects of First Generation Antihistamines
Exploring the adverse effects associated with first-generation antihistamines.
Side Effects Analysis
- First-generation antihistamines may cause sedation due to their impact on alertness levels.
- These medications can lead to activities like vertigo due to their anticholinergic effects causing dry mouth and constipation.
Differences Between Generations
Highlighting the variations in actions between first-generation and second-generation antihistamines.
Generation Disparities
- First-generation antihistamines act on H1 receptors along with other receptors leading to sedative effects.
Pharmacodynamics of Antihistamines
The discussion focuses on the pharmacodynamics of first-generation and second-generation antihistamines, highlighting differences in duration of effect, dosing frequency, and protein binding.
Pharmacodynamics Comparison
- First-generation antihistamines require more frequent administration due to shorter duration compared to second-generation antihistamines.
- Second-generation antihistamines have been designed with improved qualities but both generations are effective as antihistamines.
- Most antihistamines exhibit intermediate protein binding and active metabolites, influencing their effects.
- High protein binding is a common characteristic among antihistamines, except for a few exceptions like promethazine.
- Presentation forms of first-generation antihistamines include oral solutions, tablets, and injectables catering to varying allergic reactions' severity.
Mechanism of Action and Adverse Effects
This section delves into the mechanism of action of H1 antihistamines as competitive reversible inhibitors at the H receptor level. It also explores adverse effects associated with these medications.
Mechanism of Action
- H1 antihistamines act as competitive reversible inhibitors at the H receptor level.
- They do not cross the blood-brain barrier extensively and can have local anesthetic effects at high doses due to muscarinic receptor actions.
Adverse Effects
- Common adverse effects include sedation, dizziness, blurred vision, urinary retention, tachycardia, ventricular arrhythmias among others.
- Specific adverse effects like prolongation of QT interval are attributed to potassium channel blockade by certain antihistamine metabolites.
Cardiovascular Effects of Antihistamines
In this section, the speaker discusses the cardiovascular effects of antihistamines, focusing on the impact on the digestive system and potential side effects.
Cardiac Effects of First-Generation Antihistamines
- First-generation antihistamines can lead to various gastrointestinal issues such as vomiting, discomfort, gastric disturbances, diarrhea, and anorexia.
- Second-generation antihistamines may cause abdominal flatulence, diarrhea, and appetite stimulation. However, they are associated with non-hematological side effects like agranulocytosis and thrombocytopenia.
Safety Considerations for Pregnant Women
- Antihistamines are relatively safe for pregnant women as they do not exhibit teratogenic effects. This safety is crucial for ensuring a healthy pregnancy outcome.
Drug Interactions and Adverse Effects
- Antihistamines can interact with other medications leading to adverse effects when combined with alcohol or depressants. First-generation antihistamines can potentiate central nervous system depression when used with tricyclic antidepressants.
- They may also interact with antidepressants like monoamine oxidase inhibitors (MAOIs), increasing the risk of arrhythmias. Additionally, they can diminish the effectiveness of oral anticoagulants and corticosteroids.
Clinical Implications and Drug Interactions
This section delves into clinical implications related to drug interactions involving antihistamines.
Pharmacokinetic Considerations
- Antihistamines that are substrates of CYP3A4 enzymes can have significant implications in terms of drug interactions. These interactions affect various medications' efficacy and safety profiles.
Clinical Applications and Adverse Reactions
- The clinical uses of antihistamines extend beyond allergies to include contact dermatitis reactions, transfusion-related reactions, prophylaxis, treatment of mild to severe allergic reactions. Adrenaline plays a crucial role in managing severe reactions.
Safety Profile During Pregnancy
This part focuses on the safety profile of antihistamines during pregnancy based on observational studies rather than clinical trials.
Pregnancy Studies on Antihistamine Use
- Observational studies suggest that antihistamine use during pregnancy does not show teratogenic effects in large patient populations. However, these findings are based on surveillance data rather than controlled trials.
Specific Case Studies
- For instance, 1230 pregnant women using clemastine did not show increased risks or signs of fetal abnormalities during gestation. Similarly, no adverse outcomes were reported for hydroxyzine use during pregnancy.
Recommendations for Antihistamine Use in Pregnancy
Recommendations regarding the utilization of antihistamines during pregnancy based on available evidence from observational studies.
Utilization Guidelines
- Despite limitations in study designs due to ethical considerations around conducting clinical trials on pregnant women, observational data supports using certain antihistamines like loratadine safely during pregnancy.
Antiemetic Properties of Antihistamines
Exploring how certain antihistamines function as antiemetics particularly useful in managing conditions like hyperemesis gravidarum during pregnancy.
Antiemetic Functionality
- Certain antihistamines like dimenhydrinate act effectively as antiemetics by targeting central emetic pathways. They find extensive use in treating conditions such as hyperemesis gravidarum without adverse impacts on fetal development.
Por Vamos a Pasar AC
In this segment, the speaker mentions moving on to another topic related to alternating current (AC).
Exploring Another Topic on AC
- The speaker indicates a transition to discussing a different aspect of AC technology.