ADRIB

Indications

• Cerebral edema
• Elevated intracranial pressure
• Acute kidney injury
• Oliguria
• Glaucoma
• Renal function diagnostic aid

Dosage

Adults: For cerebral edema, administer 0

Mechanism of action

Mannitol elevates blood plasma osmolality, resulting in enhanced flow of water from tissues, including the brain and cerebrospinal fluid, into interstitial fluid and plasma. This action reduces cerebral edema and intracranial pressure. As a diuretic, it increases the osmolality of glomerular filtrate, leading to increased urinary excretion of water and preventing sodium and chloride reabsorption in the renal tubules. Mannitol also facilitates the urinary excretion of toxic substances and can help in assessing renal function by measuring glomerular filtration rate (GFR).

Pharmacodynamics

Mannitol is classified as an osmotic diuretic. It is chemically similar to other sugar alcohols but has a unique ability to promote diuresis by remaining unabsorbed in the renal tubules. Its use is indicated for conditions associated with increased body fluids, such as cerebral edema and glaucoma. Mannitol may be combined with other diuretics to enhance diuretic efficacy. Inhaled formulations are used in cystic fibrosis, though they may cause bronchospasm and hemoptysis.

Pharmacokinetics

Mannitol is freely filtered by the glomeruli with less than 10% tubular reabsorption, which allows for its urinary excretion rate to serve as a measurement of GFR. It does not undergo significant metabolism and is eliminated primarily through the kidneys. The onset of action occurs within 30 to 60 minutes after intravenous administration, with effects lasting for several hours. Administration may require monitoring of renal function and fluid balance.

Contra-indications

• Anuria
• Severe dehydration
• Severe renal impairment
• Intracranial bleeding

Adverse effects

• Asthenia
• Gastrointestinal disturbances
• Dry mouth
• Confusion
• Visual impairment
• Hypotension
• Electrolyte imbalances
• Pulmonary edema
• Hemoptysis (with inhalation use)
• Bronchospasm (with inhalation use)

Interactions

• Potassium-sparing diuretics may increase the risk of hyperkalemia
• Other diuretics may have additive effects
• Caution with nephrotoxic agents

Precautions

• Caution in patients with diabetes mellitus
• Caution in the elderly
• Caution in patients with gout
• Caution in patients with hepatic impairment
• Monitor renal function and electrolytes regularly
• May cause blue fluorescence of urine

Pregnancy

Manufacturer advises avoid due to potential toxicity in animal studies.

Breast-feeding

Manufacturer advises avoid due to lack of information available.

Storage

Store in a cool, dry place, away from light. Do not freeze.

Formulations

• Solution for injection
• Inhalation powder
• Oral solution

Indications

• Acute leukaemias
• Hodgkin's lymphoma
• Non-Hodgkin's lymphoma
• Breast cancer
• Advanced soft-tissue sarcoma
• Recurrent superficial bladder tumours
• Transitional cell carcinoma
• AIDS-related Kaposi’s sarcoma
• Advanced ovarian cancer
• Progressive multiple myeloma

Dosage

Children: Dosing for children should be adjusted according to individual treatment protocols and based on serum bilirubin concentration. Refer to the BNF for

Adults: Dosing varies by indication and should be consulted with product literature. Generally, it is administered as an intravenous injection with careful monitoring due to potential toxicity.

Mechanism of action

Doxorubicin acts by intercalating between DNA base pairs, inhibiting topoisomerase II activity, which prevents DNA replication and transcription. This leads to the generation of free radicals, causing oxidative damage to cellular components and ultimately resulting in apoptosis of cancer cells.

Pharmacodynamics

Doxorubicin's pharmacodynamic profile is characterized by its ability to inhibit DNA and RNA synthesis, leading to the disruption of cellular proliferation. The drug demonstrates a dose-dependent relationship with its cytotoxic effects, and its efficacy is significantly influenced by the duration and schedule of administration. The therapeutic window is narrow due to its associated cardiotoxicity.

Pharmacokinetics

Doxorubicin is administered intravenously and exhibits a volume of distribution of approximately 20-30 L/m². It is highly bound to plasma proteins (approximately 95%) and is metabolized primarily in the liver via reductive metabolism to active and inactive metabolites. The elimination half-life ranges from 20 to 48 hours, with renal and biliary excretion of metabolites. Cardiac function should be monitored due to the risk of cumulative dose-dependent cardiotoxicity.

Contra-indications

• Severe renal impairment
• Cardiac disease
• Previous myocardial irradiation
• Hypersensitivity to doxorubicin or any component of the formulation

Adverse effects

• Alopecia
• Anaemia
• Anxiety
• Appetite decreased
• Arrhythmias
• Arthralgia
• Asthenia
• Bone marrow depression
• Breast pain
• Cachexia
• Chest discomfort
• Chills
• Constipation
• Cough
• Decreased leukocytes
• Dehydration
• Dizziness
• Fatigue
• Hyperthermia
• Hypotension
• Increased risk of infection
• Influenza-like illness
• Infusion-related reactions
• Insomnia
• Malaise
• Mucosal abnormalities
• Muscle complaints
• Muscle weakness
• Nail disorder
• Nausea
• Nerve disorders
• Neutropenia
• Oedema
• Oral disorders
• Pain
• Scrotal erythema
• Sepsis
• Skin reactions
• Skin ulcer
• Syncope
• Taste altered
• Thrombocytopenia
• Vasodilation
• Vision blurred
• Vomiting
• Weight decreased

Interactions

• Increased risk of cardiotoxicity with other anthracyclines
• Caution with other medications that may cause myelosuppression
• Potential interaction with CYP450 inducers or inhibitors

Precautions

• Monitor cardiac function regularly due to the risk of cardiotoxicity
• Caution in patients with congestive heart failure
• Ensure effective contraception during and for at least 6 months after treatment

Pregnancy

Doxorubicin is contraindicated in pregnancy due to potential harm to the fetus. It is classified as a Category D drug.

Breast-feeding

Breastfeeding is not recommended during treatment with doxorubicin due to the potential for serious adverse reactions in the nursing infant.

Indications

• Breast cancer
• Lung cancer
• Acute lymphoblastic leukemia

Mechanism of action

Doxorubicin exerts its antineoplastic activity primarily through two mechanisms: intercalation into DNA and disruption of topoisomerase II-mediated DNA repairs. By intercalating between DNA base pairs, doxorubicin induces torsional stress, destabilizing the DNA structure and leading to nucleosome eviction. It also inhibits topoisomerase II activity, preventing the relegation of DNA breaks, thereby inhibiting DNA replication and transcription, which ultimately induces apoptosis. Additionally, doxorubicin is metabolized into a semiquinone radical, leading to the generation of reactive oxygen species that cause cellular damage and apoptosis, particularly in tumor and myocardial cells.

Pharmacodynamics

Doxorubicin is a cytotoxic, cell-cycle non-specific agent that destabilizes DNA structures through intercalation, resulting in DNA strand breakages. This disruption alters cellular transcriptomes and triggers apoptotic pathways when DNA repair fails. Furthermore, doxorubicin interferes with the activity of vital enzymes, including topoisomerase II, DNA polymerase, and RNA polymerase, leading to cell cycle arrest. The generation of cytotoxic reactive oxygen species also contributes to its efficacy and associated toxicities.

Pharmacokinetics

Doxorubicin is administered intravenously and has a volume of distribution of approximately 16-20 L/m². It is highly protein-bound (approximately 95%) and is metabolized primarily in the liver. The elimination half-life ranges from 20 to 48 hours, depending on the dosing and individual patient factors. Its clearance can be affected by hepatic function, and it is excreted mainly in bile as metabolites, with less than 5% excreted unchanged in urine. Caution is advised in patients with hepatic impairment due to potential accumulation and increased toxicity.

Contra-indications

• Severe myocardial insufficiency
• Previous hypersensitivity to doxorubicin or other anthracyclines
• Pregnancy (unless the potential benefit justifies the risk to the fetus)

Adverse effects

• Cardiotoxicity
• Nausea and vomiting
• Bone marrow suppression
• Alopecia
• Mucositis
• Secondary malignancies

Interactions

• Ciclosporin: Unknown (increases concentration)
• Leflunomide: Unknown (increases exposure)
• Teriflunomide: Unknown (increases exposure)
• Verapamil: Unknown (increases exposure)

Precautions

• Monitor cardiac function during treatment
• Assess liver function prior to and during treatment
• Cautious use in patients with pre-existing cardiac disease
• Use with caution in patients with renal impairment

Pregnancy

Doxorubicin is classified as pregnancy category D. It should only be used if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

It is not known whether doxorubicin is excreted in human milk. Caution is advised when administering to breastfeeding mothers.

Storage

Store at room temperature (20-25°C), protected from light. Keep out of reach of children.

Formulations

• Doxorubicin hydrochloride injection

Indications

• Adjustment of pH in pharmaceutical formulations
• Facilitation of drug absorption
• Used in sterile preparations

Dosage

Children: Refer to specific product guidelines for dosing information, as hydrochloric acid is typically used in a controlled setting based on formulation requirements.

Adults: Refer to specific product guidelines for dosing information, as hydrochloric acid is typically used in a controlled setting based on formulation requirements.

Mechanism of action

Hydrochloric acid dissociates in aqueous solution to release hydrogen ions (H+), leading to a decrease in pH. This acidic environment promotes the activation of pepsinogen to pepsin, an enzyme essential for protein digestion. Additionally, the acidity aids in the absorption of certain minerals and drugs that require an acidic environment for optimal bioavailability.

Pharmacodynamics

The primary pharmacodynamic action of hydrochloric acid is the maintenance of gastric acidity, which is essential for normal digestive processes. The acidic environment helps in denaturing proteins, activating digestive enzymes, and providing a barrier against pathogenic microorganisms. Its effects can influence the absorption and efficacy of various medications, particularly those that are pH-dependent.

Pharmacokinetics

Hydrochloric acid does not undergo significant systemic absorption when used in its normal contexts, as it acts locally within the gastrointestinal tract. The amount of hydrochloric acid produced by the stomach varies with food intake and physiological needs. It is secreted by parietal cells in the gastric mucosa, and its secretion is regulated by neural, hormonal, and local factors. The half-life of hydrochloric acid is not applicable as it is continuously produced and neutralized within the gastrointestinal tract.

Contra-indications

• Hypersensitivity to hydrochloric acid or any of its components
• Severe renal impairment
• Active gastrointestinal bleeding

Adverse effects

• Abdominal pain
• Diarrhea
• Nausea
• Vomiting
• Esophageal irritation
• Gastric mucosal irritation
• Electrolyte imbalances

Interactions

• May interact with alkaline substances, potentially neutralizing hydrochloric acid
• Caution with antacids as they may affect the efficacy of hydrochloric acid

Precautions

• Use with caution in patients with a history of gastritis or gastric ulcers
• Monitor electrolytes in prolonged use
• Use cautiously in patients with respiratory conditions due to potential aspiration risks

Pregnancy

Hydrochloric acid is classified as a category C drug. Use during pregnancy only if clearly needed and the potential benefits justify the risks to the fetus.

Breast-feeding

There is limited data on the excretion of hydrochloric acid in human milk. Use with caution during breastfeeding.

Storage

Store in a cool, dry place away from direct sunlight and heat. Ensure the container is tightly closed.

Formulations

• Oral solutions
• Injectable forms
• Tablets

Dosage

Children: Refer to specific guidelines for pediatric dosing; consult the BNF for Children for accurate dosage information.

Adults: Refer to specific guidelines for use; dosage may vary based on the context of use.

Mechanism of action

Hydroxide ions act primarily as bases, neutralizing acids to form water and salts. They participate in various biochemical pathways, including selenium metabolism and the degradation of reactive oxygen species. Hydroxide can influence enzyme activity and stability by altering the pH of the environment, thereby affecting metabolic reactions.

Pharmacodynamics

Hydroxide ions can impact biological processes by changing the local pH, which influences enzyme activity, ion transport, and the solubility of other compounds. Their ability to neutralize acids can help regulate physiological pH, contributing to homeostasis in living organisms.

Pharmacokinetics

As an inorganic ion, hydroxide does not undergo traditional pharmacokinetic processes like absorption, distribution, metabolism, or excretion. Instead, it is rapidly equilibrated in biological fluids and participates in acid-base reactions, having immediate effects on the local environment.

Pregnancy

There is limited information regarding the use of hydroxide during pregnancy. Consult a healthcare professional for advice.

Breast-feeding

Limited data is available on the excretion of hydroxide in breast milk. Consult a healthcare professional before use.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Indications

• Allergic conditions
• Autoimmune diseases
• Asthma and chronic obstructive pulmonary disease (COPD)
• Certain cancers (e.g., leukemia, lymphoma)
• Skin conditions (e.g., dermatitis)
• Inflammatory bowel disease
• Multiple sclerosis exacerbations
• Severe infections requiring immunosuppression

Dosage

Children: Refer to BNF for Children for specific dosing; doses vary significantly based on the child's age, weight, and condition being treated.

Adults: Refer to BNF for specific dosing; typically, initial doses range from 4 to 48 mg depending on the severity of the condition.

Mechanism of action

Methylprednisolone exerts its effects by binding to glucocorticoid receptors, leading to the modulation of gene expression. This interaction influences the transcription of anti-inflammatory proteins while suppressing the expression of pro-inflammatory genes, ultimately resulting in reduced inflammation and immune response.

Pharmacodynamics

The pharmacodynamic effects of methylprednisolone are characterized by its ability to decrease inflammation, suppress the immune response, and affect carbohydrate metabolism. Therapeutic doses lead to various systemic effects, including modification of leukocyte distribution and inhibition of cytokine production.

Pharmacokinetics

Methylprednisolone is well absorbed after oral administration, with a bioavailability of approximately 50%. It has a volume of distribution that reflects extensive tissue binding. The drug is metabolized primarily in the liver through conjugation and reduction, and its metabolites are excreted in urine. The half-life varies based on the route of administration but is generally around 18 to 36 hours.

Adverse effects

• Increased blood pressure
• Hyperglycemia
• Weight gain
• Mood changes
• Insomnia
• Gastrointestinal disturbances
• Increased susceptibility to infections

Interactions

• methylphenidate+apraclonidine: Severe (decreases effects)
• methylthioninium chloride+bupropion: Severe (increases risk of severe hypertension)
• methylphenidate+linezolid: Severe (increases risk of elevated blood pressure)
• rasagiline+methylphenidate: Severe (increases risk of a hypertensive crisis)
• mao-inhibitors+methylphenidate: Severe (increases risk of a hypertensive crisis)
• dronedarone+methylprednisolone: Moderate (increases exposure)
• miconazole+methylprednisolone: Moderate (increases concentration)
• antifungals, azoles+methylprednisolone: Moderate (increases exposure)
• crizotinib+methylprednisolone: Moderate (increases exposure)

Precautions

• Use with caution in patients with hypertension
• Monitor blood glucose levels in diabetic patients
• Consider potential for infection risk due to immunosuppression
• Evaluate for psychiatric effects in susceptible individuals

Pregnancy

Corticosteroids may be used during pregnancy if the potential benefit justifies the risk to the fetus. Careful monitoring is advised.

Breast-feeding

Corticosteroids are excreted in breast milk; caution is advised. Monitor the infant for potential effects.

Storage

Store in a cool, dry place, away from light. Keep out of reach of children.

Formulations

• Tablets
• Injectable solutions
• Topical preparations

Mechanism of action

Methylsulphate functions as a methylating agent, transferring a methyl group to nucleophiles. This process involves the formation of a sulfonium ion, which is highly reactive and can readily react with nucleophilic sites on various substrates, leading to methylation reactions.

Pharmacodynamics

The pharmacodynamics of methylsulphate is primarily related to its role as a methylating agent in biochemical reactions. It can alter the structure and function of biological molecules, potentially affecting cellular processes and signaling pathways. However, detailed pharmacodynamic studies specific to therapeutic use are limited.

Pharmacokinetics

There is limited information on the pharmacokinetics of methylsulphate, given its typical use as a reagent in laboratory settings rather than a clinical drug. When used in chemical reactions, its reactivity and transformation into other compounds would dictate its pharmacokinetic profile, which could vary significantly based on the specific context of use.

Pregnancy

There is limited data on the use of methylsulphate in pregnancy. Consult relevant guidelines.

Breast-feeding

Data on the excretion of methylsulphate in human milk is not available. Caution is advised.

Storage

Store in a cool, dry place, away from direct sunlight.

Indications

• Preservative in cosmetics
• Preservative in pharmaceuticals
• Preservative in food products

Dosage

Children: Refer to specific product guidelines as dosing varies based on formulation and concentration used.

Adults: Refer to specific product guidelines as dosing varies based on formulation and concentration used.

Mechanism of action

Parabens work by inhibiting the growth of microorganisms through their ability to disrupt the cellular processes of bacteria and fungi. They penetrate the microbial cell membrane and disrupt enzyme and protein functions, leading to cell death. Parabens are known to have low toxicity and are metabolized by the body, subsequently being excreted in urine.

Pharmacodynamics

Parabens demonstrate broad-spectrum antimicrobial activity, making them effective preservatives in various formulations. Their efficacy is influenced by factors such as concentration, pH, and the presence of other ingredients in the formulation. Due to their structural similarity to estrogen, there has been concern regarding their potential endocrine-disrupting effects, although the clinical significance of this is still debated.

Pharmacokinetics

Parabens are readily absorbed through the skin and gastrointestinal tract. Once absorbed, they are rapidly metabolized primarily in the liver. They undergo hydrolysis to form para-hydroxybenzoic acid, which is then conjugated with glucuronic acid and excreted in urine. The half-life of parabens in the human body is relatively short, and they are eliminated rapidly.

Adverse effects

• Allergic reactions, such as skin rashes
• Irritation at the site of application
• Endocrine disruption (in high concentrations)

Precautions

• Use with caution in individuals with known sensitivities or allergies to parabens
• Consider potential endocrine effects with prolonged exposure

Pregnancy

Parabens are generally considered safe in cosmetics and personal care products during pregnancy, although caution is advised due to potential endocrine disruption.

Breast-feeding

Parabens are considered safe in breastfeeding, but it is recommended to use products with minimal or no parabens when possible.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Formulations

• Topical creams
• Lotions
• Shampoos
• Conditioners
• Makeup products
• Pharmaceutical preparations

Mechanism of action

Mannitol is an osmotic diuretic that is metabolically inert in humans and occurs naturally, as a sugar or sugar alcohol, in fruits and vegetables. Mannitol elevates blood plasma osmolality, resulting in enhanced flow of water from tissues, including the brain and cerebrospinal fluid, into interstitial fluid and plasma. As a result, cerebral edema, elevated intracranial pressure, and cerebrospinal fluid volume and pressure may be reduced. As a diurectic mannitol induces diuresis because it is not reabsorbed in the renal tubule, thereby increasing the osmolality of the glomerular filtrate, facilitating excretion of water, and inhibiting the renal tubular reabsorption of sodium, chloride, and other solutes. Mannitol promotes the urinary excretion of toxic materials and protects against nephrotoxicity by preventing the concentration of toxic substances in the tubular fluid. As an Antiglaucoma agent mannitol levates blood plasma osmolarity, resulting in enhanced flow of water from the eye into plasma and a consequent reduction in intraocular pressure. As a renal function diagnostic aid mannitol is freely filtered by the glomeruli with less than 10% tubular reabsorption. Therefore, its urinary excretion rate may serve as a measurement of glomerular filtration rate (GFR). The exact mechanism of action of inhaled mannitol in the symptomatic maintenance treatment of cystic fibrosis remains unclear. It is hypothesized that mannitol produces an osmotic gradient across the airway epithelium that draws fluid into the extracellular space and alters the properties of the airway surface mucus layer, allowing easier mucociliary clearance. MANNITOL IS.../USED/ IN PROPHYLAXIS OF ACUTE RENAL FAILURE. IT IS USED FOR THIS PURPOSE IN CONDITIONS AS DIVERSE AS CARDIOVASCULAR OPERATIONS, SEVERE TRAUMATIC INJURY, OPERATIONS IN THE PRESENCE OF SEVERE JAUNDICE, AND MGMNT OF HEMOLYTIC TRANSFUSION REACTIONS. IN EACH OF THESE CONDITIONS, A PRECIPITOUS FALL IN THE FLOW OF URINE MAY BE ANTICIPATED EITHER AS THE RESULT OF AN ACUTELY REDUCED FILTRATION RATE OR FROM ACUTE CHANGES IN TUBULAR PERMEABILITY. THE LATTER MAY BE CONSEQUENCE OF THE PRESENCE OF NOXIOUS AGENT WITHIN THE TUBULAR FLUID IN EXCESSIVELY HIGH CONCN, IN SOME INSTANCES SUFFICIENT TO RESULT IN ACTUAL PRECIPITATION. IN THESE SITUATIONS, MANNITOL EXERTS OSMOTIC EFFECT WITHIN THE TUBULAR FLUID, INHIBITS WATER REABSORPTION, & MAINTAINS THE RATE OF URINE FLOW. ...CONCN OF TOXIC AGENT WITHIN TUBULAR FLUID DOES NOT REACH EXCESSIVELY HIGH LEVELS THAT OTHERWISE WOULD HAVE BEEN ACHIEVED BY MORE COMPLETE REABSORPTION OF WATER. ...EVEN THOUGH /GLOMERULAR/ FILTRATION RATE IS REDUCED, MANNITOL IS STILL FILTERED @ GLOMERULUS. THE TUBULAR IMPERMEABILITY TO MANNITOL IS NOT ALTERED BY ACUTE RENAL ISCHEMIA OF SHORT DURATION. HENCE, THE MANNITOL THAT IS FILTERED IS ALSO EXCRETED IN THE VOIDED URINE. UNREABSORBED SOLUTE LIMITS BACK DIFFUSION OF WATER. ...URINE VOL CAN BE MAINTAINED EVEN IN PRESENCE OF DECR GLOMERULAR FILTRATION.

Pharmacodynamics

Chemically, mannitol is an alcohol and a sugar, or a polyol; it is similar to xylitol or sorbitol. However, mannitol has a tendency to lose a hydrogen ion in aqueous solutions, which causes the solution to become acidic. For this reason, it is not uncommon to add a substance to adjust its pH, such as sodium bicarbonate. Mannitol is commonly used to increase urine production (diuretic). It is also used to treat or prevent medical conditions that are caused by an increase in body fluids/water (e.g., cerebral edema, glaucoma, kidney failure). Mannitol is frequently given along with other diuretics (e.g., furosemide, chlorothiazide) and/or IV fluid replacement. Inhaled mannitol has the possibility to cause bronchospasm and hemoptysis; the occurrence of either should lead to discontinuation of inhaled mannitol.

Mechanism of action

Generally, doxorubicin is thought to exert its antineoplastic activity through 2 primary mechanisms: intercalation into DNA and disrupt topoisomerase-mediated repairs and free radicals-mediated cellular damages. Doxorubicin can intercalate into DNA through the anthraquinone ring, which stabilizes the complex by forming hydrogen bonds with DNA bases. Intercalation of doxorubicin can introduce torsional stress into the polynucleotide structure, thus destabilizing nucleosome structures and leading to nucleosome eviction and replacement. Additionally, the doxorubicin-DNA complex can interfere with topoisomerase II enzyme activity by preventing relegation of topoisomerase-mediated DNA breaks, thus inhibiting replication and transcription and inducing apoptosis. Moreover, doxorubicin can be metabolized by microsomal NADPH-cytochrome P-450 reductase into a semiquinone radical, which can be reoxidized in the presence of oxygen to form oxygen radicals. Reactive oxygen species have been known to cause cellular damage through various mechanisms, including lipid peroxidation and membrane damage, DNA damage, oxidative stress, and apoptosis. Although free radicals generated from this pathway can be deactivated by catalase and superoxide dismutase, tumor and myocardial cells tend to lack these enzymes, thus explaining doxorubicin's effectiveness against cancer cells and tendency to cause cardiotoxicity. Doxorubicin hydrochloride is an antineoplastic antibiotic with pharmacologic actions similar to those of daunorubicin. Although the drug has anti-infective properties, its cytotoxicity precludes its use as an anti-infective agent. The precise and/or principal mechanism(s) of the antineoplastic action of doxorubicin is not fully understood. It appears that the cytotoxic effect of the drug results from a complex system of multiple modes of action related to free radical formation secondary to metabolic activation of the doxorubicin by electron reduction, intercalation of the drug into DNA, induction of DNA breaks and chromosomal aberrations, and alterations in cell membranes induced by the drug. Evidence from in vitro studies in cells treated with doxorubicin suggests that apoptosis (programmed cell death) also may be involved in the drug's mechanism of action. These and other mechanisms (chelation of metal ions to produce drug-metal complexes) also may contribute to the cardiotoxic effects of the drug. Doxorubicin undergoes enzymatic 1- and 2-electron reduction to the corresponding semiquinone and dihydroquinone. 7-Deoxyaglycones are formed enzymatically by 1-electron reduction, and the resulting semiquinone free radical reacts with oxygen to produce the hydroxyl radical in a cascade of reactions; this radical may lead to cell death by reacting with DNA, RNA, cell membranes, and proteins. The dihydroquinone that results from 2-electron reduction of doxorubicin also can be formed by the reaction of 2 semiquinones. In the presence of oxygen, dihydroquinone reacts to form hydrogen peroxide, and in its absence, loses its sugar and gives rise to the quinone methide, a monofunctional alkylating agent with low affinity for DNA. The contribution of dihydroquinone and the quinone methide to the cytotoxicity of doxorubicin is unclear. Experimental evidence indicates that doxorubicin forms a complex with DNA by intercalation between base pairs, causing inhibition of DNA synthesis and DNA-dependent RNA synthesis by the resulting template disordering and steric obstruction. Doxorubicin also inhibits protein synthesis. Doxorubicin is active throughout the cell cycle including the interphase. Several anthracycline-induced effects may contribute to the development of cardiotoxicity. In animals, anthracyclines cause a selective inhibition of cardiac muscle gene expression for ?-actin, troponin, myosin light-chain 2, and the M isoform of creatine kinase, which may result in myofibrillar loss associated with anthracycline-induced cardiotoxicity. Other potenti

Pharmacodynamics

Doxorubicin is a cytotoxic, cell-cycle non-specific anthracycline antibiotic. It is generally thought to exert its antitumor effect by destabilizing DNA structures through intercalation, thus introducing DNA strand breakages and damages. Not only does it alter the transcriptomes of the cells, failure in repairing DNA structures can also initiate the apoptotic pathways. Additionally, doxorubicin intercalation can also interfere with vital enzyme activity, such as topoisomerase II, DNA polymerase, and RNA polymerase, leading to cell cycle arrests. Finally, doxorubicin can also generate cytotoxic reactive oxygen species to exert cellular damages.