Pharmacology Basics

Posted on Sep 16, 2024 in Biology

Bioavailability refers to the extent a substance or drug becomes completely available to its intended biological destination(s).

The main function of progesterone is to prepare the endometrium (lining of the uterus) for a fertilized egg to implant and grow.

Agonist: A chemical substance that binds to and activates certain receptors on cells, causing a biological response.

Antagonist: A chemical substance that binds to and blocks the activation of certain receptors on cells, preventing a biological response.

Examples of Anti-Anxiety Drugs

  • Citalopram (Celexa)
  • Escitalopram (Lexapro)
  • Fluoxetine (Prozac)
  • Fluvoxamine (Luvox)
  • Paroxetine (Paxil, Pexeva)
  • Sertraline (Zoloft)

The first-line therapeutic drugs are the most effective and least toxic for use in the treatment of TB.

Bactericidal: An agent that kills bacteria.

Bacteriostatic: A drug that prevents bacterial growth and reproduction but does not necessarily kill them.

Father of Modern Pharmacology: Oswald Schmiedeberg

The definition of pharmacokinetics is the study of what the body does to a drug. It involves four main processes: absorption, distribution, metabolism, and excretion.

Examples of Carbonic Anhydrase Inhibitors

  • Acetazolamide
  • Methazolamide
  • Dorzolamide
  • Brinzolamide
  • Diclofenamide
  • Ethoxzolamide
  • Zonisamide

Antidote for Morphine: Naloxone

Functions of Oxytocin

  • Sexual arousal
  • Recognition
  • Trust
  • Romantic attachment
  • Parent-infant bonding

Several mechanisms of drug absorption have been identified, including passive diffusion, carrier-mediated membrane transport such as active and facilitated diffusion, and other nonspecific drug transporters, such as P-glycoprotein.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are medicines that are widely used to relieve pain, reduce inflammation, and bring down a high temperature. They’re often used to relieve symptoms of:

  • Headaches
  • Painful periods
  • Sprains and strains
  • Colds and flu
  • Coronavirus (COVID-19)
  • Conditions such as arthritis that can cause long-term pain

Classification of NSAIDs

  1. Non-Selective COX Inhibitors
    • Salicylates: Aspirin
    • Pyrazolone Derivatives: Phenylbutazone
    • Indole Derivatives: Indomethacin
    • Propionic Acid Derivatives: Ibuprofen
    • Aril Acetic Acid Derivatives: Diclofenac
    • Oxycame Derivatives: Piroxicam
  2. Preferential COX-2 Inhibitors: Nimesulide, Meloxicam
  3. Selective COX-2 Inhibitors: Selecoxib, Rofecoxib
  4. Analgesic Antipyretics with Poor Anti-Inflammatory Action
    • Para-aminophenol Derivatives: Paracetamol (Acetaminophen)
    • Pyrazolone Derivatives: Metamizol

The main types of NSAIDs include:

  • Ibuprofen
  • Naproxen
  • Diclofenac
  • Celecoxib
  • Mefenamic acid
  • Etoricoxib
  • Indomethacin

Their primary mechanism involves enhancing digestion and promoting bowel movements, thereby facilitating the process of bodily excretion. Laxatives can provide relief for patients with irritable bowel syndrome with constipation, chronic idiopathic constipation, and opioid-induced constipation.

Saline purgatives are salts containing highly charged ions that do not readily cross cell membranes and therefore remain inside the lumen, or passageway, of the bowel. By retaining water through osmotic forces, saline purgatives increase the volume of the contents of the bowel.

Both classes of antiulcer medications block the pathways of acid production or secretion, decreasing gastric acidity, improving symptoms and aiding in healing of acid-peptic diseases. These are some of the most commonly used drugs in medicine and are generally well tolerated and rarely result in serious adverse events.

Sedative-Hypnotic Drug

A chemical substance used to reduce tension and anxiety and induce calm (sedative effect) or to induce sleep (hypnotic effect). Most such drugs exert a quieting or calming effect at low doses and a sleep-inducing effect in larger doses.

Sedatives & Hypnotics

Sedatives: Sedatives are those drugs which reduce excitement, emotions, tension and induce calmness. It is also used as antianxiety.

Hypnotics: Hypnotics are those drugs which produce sleep, just like natural sleep.

When we increase sedative drugs dose then they produce hypnotics effects.

Sedative-hypnotic agent is a chemical substance which reduces tension and anxiety and induces calmness (sedative effect) or sleep (hypnotic effect). Low doses of these drugs exert a calming effect and higher doses have a sleep-inducing effect.

Sedative-hypnotic drugs depress the CNS

Classification

  1. Hydantoin Derivatives: Phenytoin, Methatoin, and Ethotoin
  2. Barbiturates: Phenobarbiturate, Primidone
  3. GABA Transaminase Inhibitors: Sodium Valproate, Vigabatrin
  4. GABA agonist: Gabapentin
  5. Benzodiazepines: Diazepam, Clonazepam
  6. Iminostilbenes: Carbamazepine, Oxcarbazepine

Pharmacological Action

  • These drugs stabilize cell membranes and suppress the abnormal electric impulses in the cerebral cortex.
  • They mainly work on GABA receptors, sodium and calcium channels.

Indications

  • These drugs are used to treat various types of Epilepsy:
    • Generalized (Tonic-clonic, Petit Mal)
    • Partial seizure (Simple, Complex)
    • Status

General Anaesthetics

The drugs which produce reversible loss of all sensation, consciousness and movement.

There are three components of anaesthesia:

  • Analgesia (pain killer)
  • Amnesia (loss of memory)
  • Immobilisation (loss of movement)

Classification of General Anaesthetics

  1. Inhalation Anaesthetics
    • Enflurane
    • Desflurane
    • Halothane
    • Ether
  2. Intravenous Anaesthetics
    • Thiopental sodium
    • Ketamine hydrochloride
    • Diazepam
  3. Gaseous Anaesthetics
    • Nitrous Oxide

Pharmacological Action of General Anaesthetics

These drugs work on the central nervous system and depress it, and induce sleep, loss of pain sensation and unconsciousness.

Thyroid Hormones

The thyroid gland releases triiodothyronine (T3) and thyroxine (T4). These hormones play an important role in regulation of your weight, energy levels, internal temperature, skin, hair, nail growth, metabolism and is an important part of the endocrine system.

Thyroid hormones are released by the thyroid gland and regulated by TSH (Thyroid Stimulating Hormone) which is released by the anterior pituitary gland.

Thyroid Hormones:

  • T3 (Triiodothyronine)
  • T4 (Thyroxine)
  • Reverse triiodothyronine (rT3)
  • Calcitonin

Physiological Roles

  • Thyroid hormones play a vital role in regulating metabolism, energy expenditure, and body temperature.
  • They also influence heart rate, respiratory rate, and other vital functions.
  • They play a role in growth and development, particularly in the development of the brain and nervous system.

Pathological Roles

  • Hypothyroidism occurs when the thyroid gland doesn’t produce enough hormones. This can result in a variety of symptoms, including fatigue, weight gain, and sensitivity to cold.
  • Hyperthyroidism occurs when the thyroid gland produces too much hormone. This can result in symptoms such as weight loss, rapid heartbeat, and sensitivity to heat.
  • Thyroid disorders can be caused by a variety of factors, including autoimmune disorders, iodine deficiency, and certain medications.

Clinical Uses

  • Thyroid hormone replacement therapy is used to treat hypothyroidism, a condition where the thyroid gland is not producing enough hormones.
  • Thyroid hormones can also be used to treat thyroid cancer, by suppressing the production of thyroid-stimulating hormone.
  • Thyroid hormones are also used to treat goiter, a condition where the thyroid gland enlarges, by reducing the size of the gland.

Biotransformation reactions generally are categorized as one of two types: phase I or phase II. Many drugs undergo sequential metabolism in phase I and phase II processes. Commonly, the small structural change imparted by phase I metabolism is necessary for phase II metabolism to proceed.

Estrogen

Estrogen or Oestrogen is a female sex hormone produced by the ovary, adrenal gland and placenta (during pregnancy).

This is responsible for development and control of the reproductive system and secondary sex characteristics in females.

Note: Any natural or synthetic substance which mimics the effect of a natural hormone is called estrogen.

Physiological Roles

  • Development and maintenance of female reproductive organs: Estrogen plays a vital role in the development of female reproductive organs such as the uterus, fallopian tubes, and vagina. It also helps in maintaining the function and health of these organs.
  • Development of secondary sexual characteristics: Estrogen is responsible for the development of secondary sexual characteristics in females such as the growth of breasts, distribution of body fat, and changes in body hair.
  • Bone health: Estrogen helps maintain bone density and prevent osteoporosis in both men and women.
  • Cardiovascular health: Estrogen has a protective effect on the cardiovascular system by reducing the risk of heart disease.
  • Brain function: Estrogen has an important role in cognitive function, memory, and mood regulation.

Pathological Role

  • Breast Cancer: High levels of estrogen can promote the growth of breast cancer cells.
  • Endometrial Cancer: Estrogen can increase the risk of endometrial cancer if the levels are not balanced.
  • Blood Clots: Estrogen can increase the risk of blood clots, which can lead to deep vein thrombosis or pulmonary embolism.
  • Ovarian Cancer: Estrogen can increase the risk of ovarian cancer.

Clinical Uses

  • Hormone replacement therapy: Estrogen is used in hormone replacement therapy (HRT) to alleviate symptoms of menopause such as hot flashes, vaginal dryness, and mood swings.
  • Contraception: Estrogen is used in combination with progestin as an oral contraceptive.

Side Effects of Adrenergic Drugs

The most common side effects are changes in heart rate and blood pressure. Selective binding to beta-1 receptors commonly causes tachycardia, palpitations, and hypertension. Tachyarrhythmias and anxiety can also be common. High doses may induce dangerous arrhythmias.

Insulin

Insulin is a hormone secreted by the pancreas and controls the glucose level in the bloodstream and helps in utilization of glucose by body tissues.

Physiological Role

  • Insulin helps to regulate blood glucose levels by promoting the uptake and storage of glucose in the liver, muscle, and adipose tissue.
  • It promotes the synthesis of glycogen in the liver and muscle, and inhibits the breakdown of glycogen in these tissues.
  • Insulin also enhances the uptake of amino acids by the muscle, which promotes protein synthesis and tissue growth.
  • Additionally, insulin inhibits lipolysis in adipose tissue, which reduces the release of free fatty acids into the bloodstream.

Pathological Role

  • In type 1 diabetes, the beta cells in the pancreas are destroyed, leading to a lack of insulin production and uncontrolled hyperglycemia.
  • In type 2 diabetes, the body becomes resistant to the effects of insulin, leading to elevated blood glucose levels.
  • Other conditions such as insulinoma (a rare tumor of the pancreas that secretes excess insulin) and insulin resistance syndromes can also result in abnormal insulin secretion or function.

Clinical Uses

  • Insulin is a mainstay treatment for type 1 diabetes and may also be used in certain cases of type 2 diabetes when other medications have failed.

Opioid (Narcotic) Analgesics

Analgesics are those substances which reduce pain by acting on the central nervous system.

Opioid Analgesics are pain killers that are obtained from opioids.

They reduce pain without disturbing other sensory functions, or without causing unconsciousness.

Opioid Analgesics may be natural, semi-synthetic, or synthetic.

Classification

  1. Morphine: It is a potent analgesic drug. It is also called the gold standard drug for treating severe pain. It has a high potential for addiction. E.g.: Morphine, Diamorphine, Codeine.
  2. Synthetic: Pethidine, Tramadol, Methadone, Pentazocine, Cyclazocine.

Pharmacological Action

  1. CNS: It interacts with different types of brain receptors and produces following actions:
    • Analgesia: It reduces pain sensation.
    • Euphoria: It produces a feeling of excitement and happiness.
    • Sedation: It causes sleep.
    • Vomiting: It stimulates Chemoreceptor Trigger Zone in the medulla and causes vomiting.
    • Respiratory depression: It depresses the respiratory volume, and may cause death.

Indications

  • Analgesia: They are used to relieve severe pain.
  • They are used to treat diarrhea.

Oral Hypoglycemic Agents

Oral hypoglycemic agents (OHAs) are medications used to treat type 2 diabetes by lowering blood glucose levels.

These agents work by increasing insulin sensitivity, increasing insulin secretion, or reducing glucose production in the liver.

Classification

  • Sulfonylurea: Tolbutamide, Glibenclamide, Glimepiride. They stimulate release of insulin.
  • Biguanides: Metformin, Phenformin, Buformine. They increase insulin action.
  • Meglitinide analogues: Repaglinide, Nateglinide. They directly stimulate the pancreas to release insulin.
  • Thiazolidinediones: Rosiglitazone, Pioglitazone. They decrease blood sugar levels without increasing insulin secretion.
  • α-Glucosidase Inhibitors: Miglitol, Voglibose. They inhibit the digestion of carbohydrates and decrease blood sugar levels.

Physiological Role

  • OHAs work by improving the body’s response to insulin, which is a hormone that regulates blood sugar levels.
  • OHAs can reduce insulin resistance and increase insulin sensitivity, which helps the body use glucose more effectively and lower blood sugar levels.
  • OHAs can also reduce glucose production in the liver, which can help control fasting blood sugar levels.

Pathological Role

  • OHAs are used to treat type 2 diabetes, which is a chronic condition characterized by high blood sugar levels due to insulin resistance and/or insufficient insulin secretion.
  • Type 2 diabetes can lead to complications such as cardiovascular disease, kidney disease, nerve damage, and vision loss if not properly managed.

Clinical Uses

  • OHAs are used in conjunction with lifestyle modifications such as diet and exercise to manage type 2 diabetes.
  • Different types of OHAs are available, including biguanides, sulfonylureas, meglitinides, thiazolidinediones, DPP-4 inhibitors, GLP-1 receptor agonists, and SGLT-2 inhibitors.

Classification of Anti-Emetic Drugs

  1. Anti-Cholinergic drugs: Hyoscine, Dicyclomine.
  2. H1 Anti-Histaminics: Promethazine, Diphenhydramine, Cyclizine.
  3. Neuroleptics: Chlorpromazine, Haloperidol.
  4. Prokinetic drugs: Metoclopramide, Domperidone.
  5. 5-HT3 Antagonist: Ondansetron, Granisetron.
  6. Adjuvant Anti-emetics: Dexamethasone, Benzodiazepines, Cannabinoids.

Diuretics

Drugs promoting urine output are known as diuretic drugs.

They act directly on the kidneys and primarily increase the excretion of water and ions (sodium (Na), chloride (Cl) or bicarbonates (HCO3)] from the body.

Classification

  1. High Efficacy Diuretics (Inhibitors of Na-K-2Cl Co-transport)
    • Sulphamoyl Derivatives: Furosemide, Bumetanide
    • Phenoxyacetic Acid Derivatives: Ethacrynic acid
    • Organomercurials: Mersalyl
  2. Medium Efficacy Diuretics (Inhibitors of Na-Cl Symporter)
    • Benzothiadiazines (Thiazides): Chlorothiazide, Hydrochlorothiazide, Benzthiazide, Hydroflumethiazide, Clopamide
    • Thiazide-like Diuretics (Related Heterocyclics): Chlorthalidone, Metolazone, Xipamide, Indapamide
  3. Weak or Adjunctive Diuretics
    • Carbonic Anhydrase Inhibitors: Acetazolamide
    • Aldosterone Antagonists: Spironolactone
    • Osmotic Diuretics: Mannitol, Isosorbide, Glycerol
    • Xanthines: Theophylline

Indications

  • Hypertension
  • Edema
  • Diabetes
  • Congestive Heart Failure
  • Hypercalcemia
  • Certain Kidney Diseases

Penicillin V and G can have adverse effects, including nausea, vomiting, diarrhea, rash, abdominal pain, and urticaria. In addition, Penicillin G can have other adverse reactions, including muscle spasms, fever, chills, muscle pain, headache, tachycardia, flushing, tachypnea, and hypotension.

There are two main branches of pharmacology: pharmacokinetics and pharmacodynamics.

Pharmacokinetics is defined as the study of what the body does to drugs — in other words, how drugs move around in the body, as suggested by the word ”kinetic.” Pharmacodynamics is the study of what the drugs do to the body — the mechanisms that allow a given drug to work and its general effects.

Synthesis, Storage and Release of Acetylcholine

Acetylcholine in the Peripheral Nervous System

At the presynaptic terminal, acetylcholine storage occurs within the presynaptic vesicle. With the stimulation of the presynaptic terminal, acetylcholine is released from the vesicles and into the synaptic cleft, where the neurotransmitter is free to bind with receptors.

Anti-Asthmatic Drugs

Drugs for treating asthma are divided into two categories: (1) Quick-relief medications (which are used to relieve acute asthma) and (2) Long-term asthma control medications (which are used as prophylactic measures) details below:-

  1. Quick-relief medications: They are used as needed for rapid, short-term symptom relief during an asthma attack. Types of quick-relief medications are:
    1. Short-acting beta2 agonists: These inhaled, quick-relief bronchodilators act within minutes to rapidly ease symptoms during an asthma attack. Short-acting beta2 agonists can be taken using a portable, hand-held inhaler or a nebulizer. Examples are salbutamol and terbutaline.
    2. Antimuscarinics: These inhaled antimuscarinics act quickly to immediately relax the airways, like other bronchodilators, making it easier to breathe. Examples are ipratropium and tiotropium.
    3. Systemic corticosteroids: These systemic corticosteroids (i.e., oral and intravenous routes) relieve airway inflammation caused by severe asthma. However, due to serious side effects when used long term, the systemic routes are used only on a short-term basis to treat severe asthma symptoms. Examples are prednisone and methylprednisone.
    4. Intravenous xanthines: These xanthines relax smooth muscle and to relieve bronchial spasm and are indicated for severe asthma attack. Example is aminophylline.