Macular Eye Drops

Indications

• Seborrhoeic dermatitis
• Dandruff
• Scalp psoriasis
• Bacterial infections affecting the scalp

Dosage

Children: For children, apply 3 times a week for 1 week, then apply twice weekly as needed. Refer to BNF for Children for further details.

Adults: Apply to the affected area as directed, typically 1-3 times weekly depending on the condition being treated. Refer to specific product guidelines for detailed dosing.

Mechanism of action

Benzalkonium chloride exerts its antimicrobial effect by disrupting the cell membrane of microorganisms, leading to leakage of cellular contents and ultimately cell death. This is facilitated by its cationic nature, which allows it to bind to negatively charged bacterial surfaces.

Pharmacodynamics

Benzalkonium chloride demonstrates rapid bactericidal activity, with effectiveness observed against gram-positive and gram-negative bacteria, fungi, and some viruses. Its antiseptic properties may be enhanced in the presence of moisture and are typically influenced by the concentration of the solution used.

Pharmacokinetics

Benzalkonium chloride is poorly absorbed through the skin. After topical application, it remains primarily at the site of application, where it exerts localized effects. Systemic absorption is minimal, and it is primarily eliminated through the skin and urine. However, specific pharmacokinetic data may vary based on formulation and application site.

Pregnancy

Benzalkonium chloride should be used with caution during pregnancy. Refer to specific guidelines or consult a healthcare professional.

Breast-feeding

Benzalkonium chloride should be used with caution while breastfeeding. Refer to specific guidelines or consult a healthcare professional.

Storage

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

Formulations

• Shampoo
• Soap or detergent
• Topical solution

Dosage

Children: Refer to specific drug guidelines for paediatric dosing, as this varies widely.

Adults: Refer to specific drug guidelines for adult dosing, as this varies widely.

Mechanism of action

The mechanism of action will vary depending on the specific drug referred to as 'adjust'. Generally, medications designed to 'adjust' physiological parameters may work by modulating neurotransmitter systems, altering hormonal levels, or affecting enzyme activity to achieve therapeutic effects.

Pharmacodynamics

Pharmacodynamics will depend on the specific drug, but typically involves the interaction of the drug with its receptor sites, leading to a biological response. The efficacy and potency of the drug are influenced by its affinity for the target receptors and the subsequent signaling pathways activated.

Pharmacokinetics

Pharmacokinetics, including absorption, distribution, metabolism, and excretion, will vary by drug. Common factors influencing pharmacokinetics include bioavailability, half-life, and the presence of food or other drugs that may affect the drug's metabolism and elimination from the body.

Indications

• Disinfection of surfaces
• Antiseptic for skin
• Preservative in pharmaceuticals
• Treatment of minor cuts and abrasions

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations in pediatric populations.

Adults: Refer to the BNF for specific formulations and concentrations as doses may vary based on the application and preparation.

Mechanism of action

The bactericidal action of benzalkonium chloride is believed to result from the disruption of intermolecular interactions, which leads to the dissociation of cellular membrane lipid bilayers in bacteria. This disruption compromises cellular permeability, causing leakage of vital cellular contents. Moreover, the agent can deactivate important molecular complexes such as enzymes that regulate various respiratory and metabolic activities within the cells. Cationic surfactants like benzalkonium chloride can thus effectively disrupt critical intermolecular interactions and tertiary structures in biochemical systems, impairing bacterial function.

Pharmacodynamics

Benzalkonium chloride is classified as a biocidal agent with a relatively long duration of action. It exhibits a spectrum of activity against various microorganisms, including bacteria, certain viruses, fungi, and protozoa; however, it is ineffective against bacterial spores. The agent tends to demonstrate greater efficacy against gram-positive bacteria compared to gram-negative ones. The mode of action can be bacteriostatic (preventing growth) or bactericidal (killing bacteria), depending on its concentration. The activity of benzalkonium chloride is generally stable across different pH levels but is enhanced at elevated temperatures and with extended exposure.

Pharmacokinetics

The pharmacokinetic properties of benzalkonium chloride, including absorption, distribution, metabolism, and excretion, are not fully characterized. Its topical application limits systemic exposure, and it primarily exerts localized effects at the site of application. The duration of action and efficacy may be influenced by the formulation and concentration used.

Pregnancy

Benzalkonium chloride is generally considered safe for use during pregnancy when applied topically, but systemic absorption should be minimized. Always consult a healthcare provider for use during pregnancy.

Breast-feeding

Benzalkonium chloride is considered safe for topical application during breastfeeding, but care should be taken to avoid exposure to the infant. Consultation with a healthcare provider is recommended.

Storage

Store at room temperature, away from moisture and heat. Keep in a tightly closed container, protected from light.

Formulations

• Topical solution
• Disinfectant wipes
• Liquid antiseptics

Indications

• Electrolyte replacement
• Volume expansion in hypovolemic patients
• Management of hyponatremia
• Support in intravenous fluid therapy

Dosage

Children: Refer to the BNF for Children for appropriate dosing in paediatric patients, as dosages may vary based on the formulation and clinical condition.

Adults: Refer to specific product information or clinical guidelines for dosage recommendations, as disodium is often part of combination products.

Mechanism of action

Disodium compounds often function by providing sodium ions that are essential for various physiological processes. Sodium ions play a critical role in maintaining osmotic balance, nerve impulse transmission, and muscle contraction. In the context of intravenous solutions, disodium helps to restore electrolyte balance in patients.

Pharmacodynamics

The pharmacodynamics of disodium is primarily related to its role in electrolyte balance and fluid homeostasis. Sodium ions are vital for the function of excitable tissues, including neurons and muscle cells. Changes in sodium levels can affect blood pressure, hydration status, and overall cellular function.

Pharmacokinetics

The pharmacokinetics of disodium compounds depend on their specific formulation and route of administration. When administered intravenously, disodium is rapidly distributed in the extracellular fluid, where it helps to maintain osmotic pressure. Sodium is primarily excreted by the kidneys, and its levels can be influenced by fluid intake, dietary sodium, and renal function.

Pregnancy

Use with caution. Consult a healthcare provider for specific guidance.

Breast-feeding

Use with caution. Consult a healthcare provider for specific guidance.

Storage

Store at room temperature, away from moisture and direct sunlight.

Indications

• Lead poisoning
• Mercury poisoning
• Calcium overload
• Certain diagnostic procedures involving heavy metals

Dosage

Children: Refer to the BNF for Children for appropriate dosing information tailored for paediatric patients.

Adults: Refer to the BNF for specific dosing guidelines based on the condition being treated, considering factors such as the severity of metal poisoning and renal function.

Mechanism of action

Edetate functions by forming stable complexes with divalent and trivalent metal ions, including lead and calcium, through its multiple carboxylate and amine groups. This chelation renders the metals more soluble and promotes their renal excretion, thereby reducing their toxic effects in the body.

Pharmacodynamics

The chelation of metals by edetate decreases the free metal concentration in the bloodstream, which mitigates the toxic effects associated with heavy metal accumulation. The efficacy of edetate in removing metals such as lead has been well documented, and its ability to bind calcium can influence calcium homeostasis in certain clinical scenarios.

Pharmacokinetics

Edetate is administered intravenously, with rapid distribution throughout the extracellular fluid. It is primarily excreted unchanged by the kidneys. The onset of action occurs quickly after administration, and the duration depends on the dose and the patient's renal function. The elimination half-life is approximately 1 hour but may vary based on renal clearance.

Contra-indications

• Hypersensitivity to edetate or any component of the formulation
• Severe renal impairment
• Active bleeding disorders

Adverse effects

• Hypocalcemia
• Nausea
• Vomiting
• Diarrhea
• Abdominal pain
• Headache
• Rash
• Fever

Interactions

• May enhance the effects of anticoagulants
• Concurrent use with calcium supplements may reduce effectiveness
• May interfere with the absorption of certain medications due to changes in gastrointestinal motility

Precautions

• Use with caution in patients with renal impairment
• Monitor electrolyte levels, particularly calcium, during treatment
• Assess the patient's hydration status before administration

Pregnancy

Limited data on the use of edetate in pregnancy. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Caution is advised as it is not known whether edetate is excreted in human milk. Weigh the risks and benefits before use.

Storage

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

Formulations

• Edetate disodium injection
• Edetate calcium disodium 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

• Management of moderate to severe pain
• Post-operative pain relief
• Short-term treatment of pain when oral therapy is not possible

Dosage

Adults: For adults, the initial dose is typically 10 mg

Mechanism of action

Ketorolac inhibits key pathways in prostaglandin synthesis which is crucial to its mechanism of action. It is a non-selective inhibitor of both COX-1 and COX-2 enzymes, with clinical efficacy primarily derived from its inhibition of COX-2. This enzyme converts arachidonic acid to prostaglandins, mediators of inflammation and pain. By blocking this pathway, ketorolac achieves analgesia and reduces inflammation.

Pharmacodynamics

As a non-selective NSAID, ketorolac acts by inhibiting COX-1 and COX-2 enzymes. COX-1 is constitutively active and present in various tissues, while COX-2 is inducible and primarily involved in inflammatory responses. While inhibition of COX-2 leads to the desired anti-inflammatory and analgesic effects, inhibition of COX-1 is associated with increased risks of gastrointestinal bleeding, ulceration, and other serious side effects. Therefore, ketorolac is recommended for short-term use only.

Pharmacokinetics

Ketorolac is well-absorbed following oral administration, with peak plasma concentrations occurring within 1 to 2 hours. It has a volume of distribution of approximately 0.15 L/kg and is metabolized primarily in the liver via glucuronidation and hydroxylation. The elimination half-life is about 5 to 6 hours in healthy adults, and the drug is excreted mainly in urine, with about 90% of the dose recovered as metabolites.

Contra-indications

• Active or history of peptic ulcer disease
• History of gastrointestinal bleeding or perforation
• Severe renal impairment
• Hypersensitivity to ketorolac or other NSAIDs
• Concurrent use with other NSAIDs
• Labor and delivery
• Active bleeding conditions

Adverse effects

• Gastrointestinal bleeding
• Peptic ulcers
• Perforation of the gastrointestinal tract
• Renal impairment
• Cardiovascular events
• Headache
• Dizziness
• Nausea
• Abdominal pain

Interactions

• Anticoagulants (increased risk of bleeding)
• Other NSAIDs (increased risk of adverse effects)
• Lithium (reduced renal clearance)
• Methotrexate (increased toxicity)
• Diuretics (reduced effectiveness)

Precautions

• Use with caution in patients with a history of gastrointestinal disease
• Monitor renal function in long-term use
• Caution in the elderly due to increased risk of adverse effects
• Avoid in patients with a history of asthma or allergic reactions to NSAIDs

Pregnancy

Use is contraindicated during pregnancy, especially in the third trimester due to the risk of fetal harm and complications during delivery.

Breast-feeding

Caution is advised; ketorolac is excreted in breast milk and may affect the nursing infant.

Storage

Store at room temperature, away from moisture and heat. Protect from light.

Formulations

• Tablets
• Injection solution

Indications

• Spermicide for contraception
• Topical antiseptic in personal care products

Dosage

Children: Refer to specific product guidelines for dosing instructions as formulations vary.

Adults: Refer to specific product guidelines for dosing instructions as formulations vary.

Mechanism of action

Octoxynol acts as a surfactant, lowering the surface tension of membranes. It disrupts the lipid bilayer of spermatozoa, leading to increased permeability and ultimately cell lysis. This mechanism results in the immobilization of sperm, preventing them from traversing the cervical mucus and reaching the ovum.

Pharmacodynamics

The pharmacodynamic profile of octoxynol includes its ability to immobilize sperm and reduce their viability through membrane disruption. The efficacy of octoxynol as a spermicide is influenced by factors such as concentration, exposure time, and the presence of other agents in formulations. It is generally effective upon contact, providing immediate action.

Pharmacokinetics

Octoxynol is not systemically absorbed in significant amounts when used as a topical contraceptive. Its primary action occurs locally at the site of application. The elimination half-life is not well characterized given its limited systemic absorption, but it is presumed to be excreted primarily through feces and urine in its unchanged form.

Adverse effects

• Skin irritation
• Allergic reactions
• Localized dermatitis

Precautions

• Use with caution in individuals with sensitive skin
• Avoid contact with eyes

Pregnancy

Safety during pregnancy has not been established. Use only if potential benefits justify the risks.

Breast-feeding

Safety during breastfeeding has not been established. Use with caution.

Storage

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

Formulations

• Topical cream
• Gel

Indications

• Metabolic acidosis
• Acute kidney injury
• Cardiac arrest
• Severe lactic acidosis

Dosage

Children: Refer to BNF for Children for appropriate dosing in paediatric patients.

Adults: Refer to BNF for specific dosing guidelines based on clinical condition and severity of acidosis.

Mechanism of action

Tromethamine functions as a proton acceptor, interacting with hydrogen ions and their associated acid anions. It combines with lactic, pyruvic, and other metabolic acids, as well as carbonic acid, facilitating their excretion in urine. At physiological pH, tromethamine exists in both ionized and un-ionized forms, with the latter capable of penetrating cell membranes to neutralize intracellular acids. By reducing hydrogen ion concentration, tromethamine alters the bicarbonate:carbonic acid buffer system, increasing bicarbonate levels while decreasing carbon dioxide tension, which may lead to hypoventilation.

Pharmacodynamics

As an alkalinizing agent, tromethamine increases bicarbonate concentrations in the blood, thereby helping to correct metabolic acidosis. Its ability to act as a weak osmotic diuretic contributes to increased urine output and the excretion of electrolytes. This dual action is beneficial in managing conditions characterized by acid-base imbalances.

Pharmacokinetics

After intravenous administration, tromethamine is rapidly distributed in the body. It is primarily excreted unchanged in the urine, with its alkalinizing effects lasting until the body's regulatory mechanisms restore acid-base balance. The pharmacokinetics are influenced by the ionization state of the drug, which varies with pH levels.

Adverse effects

• Hypoventilation
• Hypoxia
• Fluid and electrolyte imbalances
• Metabolic alkalosis
• Nausea
• Vomiting

Precautions

• Use with caution in patients with respiratory depression
• Monitor patients for signs of fluid overload
• Assess electrolyte levels regularly during treatment

Pregnancy

There are no adequate and well-controlled studies in pregnant women. Tromethamine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

It is not known whether tromethamine is excreted in human milk. Caution should be exercised when administering tromethamine to a nursing mother.

Storage

Store at room temperature, away from light and moisture. Do not freeze.

Formulations

• Injection solution

Mechanism of action

Although not entirely elucidated, the bactericidal action of benzalkonium chloride is believed to be due to the disruption of intermolecular interactions. Such disruption can cause the dissociation of cellular membrane lipid bilayers of bacteria, resulting in compromised cellular permeability control and the leakage of important cellular contents. Additionally, other important molecular complexes like enzymes which control the maintenance of a great range of respiratory and metabolic cellular activities, are also susceptible to such deactivation. Consequently, a variety of critical intermolecular interactions and tertiary structures in very highly specific biochemical systems that allow bacterial agents to function normally can be readily disrupted or deactivated by cationic surfactants like benzalkonium chloride..

Pharmacodynamics

Benzalkonium chloride solutions are generally categorized as biocidal agents with relative long durations of action. Their spectrum of activity has been demonstrated against bacteria, to some viruses, fungi, and protozoa, although bacterial spores are treated as being resistant to the agent. Additionally, the agent generally shows more activity against gram-positive than gram-negative bacteria. Finally, solutions of benzalkonium chloride are bacteriostatic or bactericidal based on their concentration. Bacteriostatic agents act to prevent further growth of bacterial organisms that are present while bactericidal agents function to kill bacteria that are present. In general, the activity of the agent is not largely affected by pH, but such activity does increase substantially at higher temperatures and prolonged exposure times.

Mechanism of action

Ketorolac inhibits key pathways in prostaglandin synthesis which is crucial to it's mechanism of action. Although ketorolac is non-selective and inhibits both COX-1 and COX-2 enzymes, it's clinical efficacy is derived from it's COX-2 inhibition. The COX-2 enzyme is inducible and is responsible for converting arachidonic acid to prostaglandins that mediate inflammation and pain. By blocking this pathway, ketorolac achieves analgesia and reduces inflammation. Ketorolac is administered as a racemic mixture; however, the "S" enantiomer is largely responsible for it's pharmacological activity.

Pharmacodynamics

Ketorolac is a non-selective NSAID and acts by inhibiting both COX-1 and COX-2 enzymes which are normally responsible for converting arachidonic acid to prostaglandins. The COX-1 enzyme is constitutively active and can be found in platelets, gastric mucosa, and vascular endothelium. On the other hand, the COX-2 enzyme is inducible and mediates inflammation, pain and fever. As a result, inhibition of the COX-1 enzyme is linked to an increased risk of bleeding and risk of gastric ulceration, while the desired anti-inflammatory and analgesic properties are linked to inhibition of the COX-2 enzyme. Therefore, despite it's effectiveness in pain management, ketorolac should not be used long-term since this increases the risk of serious adverse effects such as gastrointestinal bleeding, peptic ulcers, and perforations.

Mechanism of action

Tromethamine is an alkalinizing agent which acts as a proton (hydrogen ion) acceptor. Tromethamine is a weak base; following IV injection, it attracts and combines with hydrogen ions and their associated acid anions and the resulting salts are excreted in urine. Tromethamine can combine with lactic, pyruvic, and other metabolic acids and with carbonic acid. ... At pH 7.4, approximately 70% of the tromethamine present in plasma is in the ionized (protonated) form; if pH is decreased from pH 7.4, the ionized fraction of the drug is increased. In contrast to the ionized fraction of tromethamine, which upon administration reacts only with acid in the extracellular fluids, the fraction of the dose which remains un-ionized at physiologic pH is thought to be capable of penetrating the cell membrane to combine with intracellular acid. Since administration of tromethamine reduces hydrogen ion concentration, there is a decrease in proton donor and an increase in proton acceptor concentrations in body buffers. In the bicarbonate:carbonic acid buffer, the concentration of dissolved carbon dioxide is decreased (at least until regulatory mechanisms compensate) and the concentration of bicarbonate is increased. The reduction of carbon dioxide tension removes a potent stimulus to breathing and may result in hypoventilation and hypoxia. Tromethamine ... acts as a weak, osmotic diuretic, increasing the flow of alkaline urine containing increased amounts of electrolytes. By removing protons from hydronium ions, ionization of carbonic acid is shifted so as to decrease pCO2 and to increase bicarbonate. Excess bicarbonate is then gradually excreted in kidney. /Tromethamine is an/ especially useful way to manage excessively high pCO2 in respiratory acidosis...