- Get link
- Other Apps
- Get link
- Other Apps
INDUCTION,
INHIBITION OF DRUG METABOLISM AND INHIBITION OF BILIARY EXCRETION
Induction
and Inhibition
- Metabolism based drug-drug
and other¢ interactions can have a
significant influence on the use and safety of many drugs.
- Induction of drug metabolism
can lead to¢ unexpected drops in drug
concentration or the build-up of metabolites.
- The reverse can occur when
there is inhibition of drug metabolism.
- The major organ involved in
metabolism is liver¢ and the major enzyme system
involved in drug metabolism is CYP 450.
Induction
- The
phenomenon of increased drug metabolizing ability of the enzymes by
several drugs and chemicals is called as enzyme induction.
- A number of drugs can cause an increase
in liver enzyme activity over time. This in turn can increase the
metabolic rate of the same or other drugs.
- Ex: phenobarbitone will
induce the metabolism of itself, phenytoin, warfarin.
- Dosing rates may need to be
increased to maintain effective plasma concentrations.
Hormone
induced CYP 450 expression:
- Hormones induce induction of
certain drugs like¢ tamoxifen, tacrine,
acetaminophen and xenobiotics like dietary phytochemicals and carcinogens
like aromatic amines produced in cooking and those found in cigarette
smoke.
Induction by inhibition interaction:
- Insoniazid, ethanol and some
xenobiotics induced CYP 2E1¢ and CYP3A1.
- Well known example is
induction of CYP2E1 by isoniazid and CYP3A1 by macrolide antibiotics.
Most
Enzyme Inducers have following properties:
- They are lipophilic
compounds.
- They are substrate for the
induced enzyme system.
- They have long elimination
half lives.
Mechanisms
involved in enzyme induction are:
- Increase in both liver size
and liver blood flow.
- Increase in both total and
microsomal protein content.
- Increase in stability of
enzymes.
- Increase in synthesis of
cytochrome P-450.
- Proliferation of smooth
endoplasmic reticulum.
Consequences
of enzyme induction includes:
- Decrease in pharmacological
activity of drugs.
- Increase in activity where
the metabolites are active.
- Altered physiological status
due to enhanced metabolism of endogenous compounds such as sex hormones.
Inhibition
- The phenomenon of decreased
drug metabolizing¢ ability of the enzymes by
several drugs and chemicals is called as enzyme inhibition.
- The process of inhibition
may be of two types:
Ø [1]. Direct Inhibition [2]. Indirect Inhibition
- Direct Inhibition:- It may result from the interaction
of enzyme site, the outcome being a change in enzyme activity.
- Direct inhibition can occur
by one of the three mechanisms:
- Competitive inhibition:Eg: Methacholine inhibits
metabolism of Ach by¢ competing with it for
cholinesterase.
- Non-competitive inhibition: Eg: Isoniazid inhibits the
metabolism of Phenytoin¢ by the same enzymes.
- Product Inhibition: Eg:
Xanthine Oxidase inhibitors (Allopurinol) and¢ MAO inhibitors (Phenelzine)
also inhibits the enzyme activity directly.
- Indirect Inhibition;- It is brought about by one
of the two mechanisms:
Ø Repression: is defined as the
decrease in¢ enzyme content.
Ø Altered physiology: due to
nutritional¢ defficiency or hormonal imbalance.
- Enzyme inhibition is more
important clinically than enzyme induction, especially for drugs with
narrow therapeutic index, Eg: anticoagulants, antiepileptics,
hypoglycemics.
Inhibition
of Biliary Excretion
- Drug interactions in biliary
excretion: Drugs or often conjugated
and excreted in bile. Some drugs are excreted in bile biotransformation.
Eg: In humans most water soluble drugs and metabolites of relatively high
molecular weight are excreted largely in the bile.
- This excretion is mainly via
transporters and possibility exists for drug interaction with concomitant
administration.
- Hepatobiliary Drug
Interaction: The
co-administration of drugs which inhibits the co-transporter involved in
biliary excretion can reduce the biliary excretion of drug , leading to
elevated plasma drug concentration. Eg: Biliary and urinary of digoxin
Effect
on biliary excretion:
- Verapamil and cyclosporine
are both inhibitors of p-gp, but through different mechanism, verapamil is
a substrate for p-gp and is a competitive inhibitor of this pump, where as
cyclosporine inhibit transport function by interfering with substrate
recognition and ATP hydrolysis.
- Decrease clearance of drug
through inhibition of p-gp translates¢ clinically in to increased
AUC and increased in toxicity. Examples:¢ * Decreased in vincristine
clearance in presence of verapamil.
antibiotics
cytochrome p 450
drug
drug excretion
drug netabolism
enzymes
induction
inhibition
medication
medicines
pharmacogenomics
pharmacology
- Get link
- Other Apps
Interesting content
ROLE OF OPIORPHINS IN THE MANAGEMENT OF PAIN
What is pain: pain is any noxious, unpleasant, subjective and emotional experience associated with actual or potential tissue damage. Based on the mechanism, pain is of different types 1. Nociceptive pain 2. Neuropathic pain 3. Functional pain Based on the duration, pain is either acute or chronic . Physiological mechanism in the body to painful stimuli : stimulation of the nerve endings known as nociceptors is the 1 st step leading to the sensation of pain. These receptors are found in both visceral and somatic structures and are due to mechanical, chemical and electrical factors. The action potential that is produced due to the stimuli travels along the spinal cord and reaches higher cortical centers where the pain is processed. In some cases pain is produced due to nerve damage as in diabetic neuropathy, neuralgia etc., is such situations due to abnormal operation of the nervous system pain circuits may rewire themselves and produces spontaneous nerve
Healthcare insights: Over view of Beta Blockers
Beta blockers, also known as beta-adrenergic blocking agents, are a class of medications primarily used to manage cardiovascular conditions. They work by blocking the effects of adrenaline (epinephrine) on the beta-adrenergic receptors, which are part of the sympathetic nervous system. By doing so, they help reduce heart rate, decrease blood pressure, and lessen the heart's workload. Pharmacology of Beta Blockers Mechanism of Action Beta blockers inhibit the action of catecholamines, particularly adrenaline and noradrenaline, on beta-adrenergic receptors. These receptors are found throughout the body, but are most notably present in the heart, lungs, and vascular smooth muscle. Beta-1 Receptors: Predominantly located in the heart. Blocking these receptors reduces heart rate, decreases myocardial contractility, and suppresses the rate of atrioventricular (AV) conduction, leading to lower blood pressure and reduced myocardial oxygen demand. Beta-2 Rec
Understanding Drug-Drug Interactions (DDIs)
Understanding Drug-Drug Interactions (DDIs) What are Drug-Drug Interactions (DDIs)? Drug-Drug Interactions (DDIs) occur when one drug affects the activity, efficacy, or toxicity of another drug when both are administered together. These interactions can either increase or decrease the effectiveness of one or both drugs or lead to adverse effects. Types of Drug-Drug Interactions Pharmacokinetic Interactions : Affect the absorption, distribution, metabolism, or excretion of a drug, thereby altering its concentration in the bloodstream. Absorption : One drug can affect the gastrointestinal absorption of another. Distribution : Drugs can compete for protein binding sites, affecting distribution. Metabolism : Enzyme induction or inhibition can affect drug metabolism. Excretion : Drugs can affect the renal excretion of each other. Pharmacodynamic Interactions : Affect the action or effect of a drug without changing its concentration in the bloodstream. Synergistic : Combined effect is great
CHEESE REACTION
CHEESE REACTION Introduction The "cheese reaction" refers to a serious and sometimes life-threatening condition that can occur in individuals who consume foods high in tyramine while taking monoamine oxidase inhibitors (MAOIs). This reaction is characterized by a sudden and severe increase in blood pressure, which can lead to hypertensive crises. The term "cheese reaction" originates from the association of the reaction with aged cheeses, which are known to have high levels of tyramine. This comprehensive overview explores the pathophysiology, clinical manifestations, diagnosis, management, and prevention of the cheese reaction. Historical Context The discovery of the cheese reaction dates back to the mid-20th century when MAOIs were introduced as antidepressants. Patients taking MAOIs were found to develop severe hypertensive episodes after consuming certain foods, particularly aged cheeses. This observation led to the identification of tyramine as the c
Clinical Significance of Thiopurine S-Methyltransferase (TPMT)
Clinical Significance of Thiopurine S-Methyltransferase (TPMT) importance of TPMT testing in clinical practice https://www.instagram.com/p/C7ZVQlGCaz-/?igsh=MWs4bjZ3aWQ0OGhqeA== Introduction to TPMT Thiopurine S-methyltransferase (TPMT) is a cytosolic enzyme that plays a pivotal role in the metabolism of thiopurine drugs, including azathioprine (AZA), 6-mercaptopurine (6-MP), and 6-thioguanine (6-TG). These drugs are crucial in the treatment of various medical conditions such as leukemia, autoimmune diseases, and organ transplant rejection. Genetic Polymorphism and TPMT Activity TPMT activity varies significantly among individuals due to genetic polymorphisms. These polymorphisms lead to different levels of enzyme activity, which can be broadly categorized into high, intermediate, and low/absent activity. Approximately 90% of individuals have high TPMT activity, around 10% have intermediate activity, and about 0.3% have low or absent activity. Role of TPMT in Thiopurine Metabo
CLOPIDOGREL DRUG - DRUG INTERACTIONS WITH PPI'S
Never use pantoprazole with clopidogrel because clopidogrel is a prodrug and it requires cytochrome p450 isoenzyme CYP2C19 for its bioactivation, On the other hand pantoprazole inhibits this isoenzyme CYP2C19 during its metabolism eventually leading to inhibition of clopidogrel bioactivation If a patient is on both Clopidogrel and Pantoprazole or any other Proton pump inhibitors, Its better to replace them with Rabeprazole which has no effect on Clopidogrel bio-activation as it doesn't inhibit CYP2C19 isoenzyme. Clopidogrel, marketed under the brand name Plavix among others, is an antiplatelet medication commonly used to prevent blood clots in various cardiovascular conditions. It is particularly effective in patients who have suffered from heart attacks, strokes, or those diagnosed with peripheral artery disease. Here is a comprehensive overview of clopidogrel, covering its mechanism of action, indications, usage, side effects, and considerations. Mechanism of Action Clopidogrel
Healthcare insights: Serotonin Syndrome
Serotonin Syndrome is a potentially life-threatening condition caused by excessive accumulation of serotonin in the brain. It usually results from the use of medications or substances that increase serotonin levels or affect its metabolism Causes of Serotonin Syndrome Medication Overdose : Taking too much of a drug that increases serotonin. Drug Interactions : Combining multiple drugs that affect serotonin levels. Common culprits include: SSRIs (e.g., fluoxetine, sertraline) SNRIs (e.g., venlafaxine, duloxetine) TCAs (e.g., amitriptyline, nortriptyline) MAOIs (e.g., phenelzine, selegiline) Serotonin Precursors (e.g., tryptophan, 5-HTP) Other Medications : Certain painkillers (tramadol), migraine medications (triptans), anti-nausea drugs (ondansetron), and some illicit drugs (MDMA, LSD) Herbal Supplements : Such as St. John’s Wort. Recreational Drugs : Use of drugs like MDMA (Ecstasy) and LSD. Symptoms of Serotonin Syndrome Symptoms c
The Healing power of Nature
The Healing power of Nature Introduction: In the hustle and bustle of modern life, amidst the concrete jungles and technology-driven existence, there exists a profound longing for a simpler, more tranquil connection with nature. Roaming in green fields offers a profound antidote to the stresses of everyday life, providing a therapeutic escape and fostering a sense of joy and well-being. This article delves into the scientific evidence behind the profound effect that immersing oneself in nature, particularly green fields, has on human happiness. The Psychological Impact of Green Spaces: Numerous studies have elucidated the positive impact of green spaces on mental health and well-being. The term "biophilia hypothesis," coined by Edward O. Wilson, suggests that humans have an innate affinity for nature, rooted in our evolutionary history. When we immerse ourselves in greenery, whether it's a sprawling meadow or a serene forest, we tap into this deep
Inhibitors and inducers of Cytochrome P450
Mastering Emergency medications
Mastering emergency medications List of some common emergency medications along with their dosages and dilutions for different conditions: Epinephrine (Adrenaline) Indications : Anaphylaxis, cardiac arrest, asthma exacerbation Anaphylaxis : Adult : 0.3-0.5 mg IM, repeated every 5-15 minutes as needed. Pediatric : 0.01 mg/kg IM, up to a maximum of 0.3 mg per dose, repeated every 5-15 minutes as needed. Concentration : 1 mg/mL (1:1,000) Cardiac Arrest : Adult : 1 mg IV/IO every 3-5 minutes during resuscitation. Pediatric : 0.01 mg/kg IV/IO every 3-5 minutes during resuscitation. Concentration : 0.1 mg/mL (1:10,000) Asthma Exacerbation : Adult : 0.3-0.5 mg IM or SC every 20 minutes for up to 3 doses. Pediatric : 0.01 mg/kg IM or SC, up to a maximum of 0.3 mg per dose, every 20 minutes for up to 3 doses. Concentration : 1 mg/mL (1:1,000) Norepinephrine (noradrenaline) is primarily used in the mana