Lenacapavir Gilead

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

• Constipation
• Dietary fiber supplementation
• Irritable bowel syndrome
• Diverticular disease
• Weight management

Dosage

Children: Refer to appropriate guidelines for specific dosage; generally taken with adequate fluid intake.

Adults: Refer to appropriate guidelines for specific dosage; generally taken with adequate fluid intake.

Mechanism of action

Cellulose acts primarily as a bulk-forming laxative. It absorbs water in the intestines, which increases stool bulk and stimulates peristalsis, thus facilitating bowel movements. Additionally, cellulose is not digestible by human enzymes, leading to fermentation by gut bacteria, which may enhance gut health and alter gut microbiota composition.

Pharmacodynamics

Cellulose increases stool weight and frequency of bowel movements. It works by retaining water in the intestines, leading to softer stools and improved passage through the gastrointestinal tract. The bulking effect of cellulose can help alleviate constipation and promote overall digestive health. It may also play a role in cholesterol reduction and glycemic control through its effects on digestion and absorption of nutrients.

Pharmacokinetics

Cellulose is not absorbed into the bloodstream due to its indigestible nature. Instead, it passes through the gastrointestinal tract, where it adds bulk to the stool. Its fermentation by colonic bacteria produces short-chain fatty acids, which may have beneficial effects on colon health. The onset of action for cellulose as a laxative can vary but is generally within 24 to 72 hours after ingestion.

Adverse effects

• Bloating
• Flatulence
• Diarrhea
• Abdominal discomfort

Precautions

• Use with caution in patients with a history of gastrointestinal disorders.
• Monitor for potential allergic reactions in sensitive individuals.

Pregnancy

Cellulose is generally considered safe during pregnancy as it is a non-toxic, indigestible fiber.

Breast-feeding

Cellulose is also considered safe during breastfeeding; it is excreted in breast milk in negligible amounts.

Storage

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

Formulations

• Powder
• Capsules
• Tablets
• Granules

Indications

• Used as a binder in tablet formulations
• Acts as a stabilizer in liquid formulations
• Serves as a film-forming agent in topical preparations

Dosage

Children: Refer to specific formulations for guidance; dosages will vary based on the formulation and therapeutic use.

Adults: Refer to specific formulations for guidance; dosages will vary based on the formulation and therapeutic use.

Mechanism of action

Copovidone acts primarily as a binder in solid dosage forms. It forms a cohesive gel in the presence of moisture, which helps in the agglomeration of powder particles, thus improving the mechanical strength and integrity of tablets. Additionally, copovidone can enhance drug solubility and dissolution rate, thereby facilitating better absorption of active pharmaceutical ingredients.

Pharmacodynamics

As a polymer, copovidone does not exert a pharmacological effect in the traditional sense but plays a crucial role in the pharmaceutical formulation process. It aids in the uniform distribution of active ingredients and can enhance the stability of formulations, thereby ensuring consistent therapeutic efficacy. Its properties allow for the sustained release of drugs when used in controlled-release formulations.

Pharmacokinetics

Copovidone is not absorbed in the gastrointestinal tract and therefore does not exhibit systemic pharmacokinetics. Instead, it remains in the gastrointestinal lumen, where it can affect the release and absorption of other co-administered drugs. Its degradation products are typically non-toxic and are excreted without causing harm to the body.

Adverse effects

• Hypersensitivity reactions
• Nausea
• Vomiting
• Diarrhea
• Abdominal pain

Precautions

• Use with caution in patients with known allergies to polyvinyl compounds
• Evaluate risk of allergic reactions in sensitive individuals

Pregnancy

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

Breast-feeding

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

Storage

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

Formulations

• Oral tablets
• Capsules
• Topical ointments

Indications

• Used as a disintegrant in tablet formulations
• Enhances the bioavailability of active pharmaceutical ingredients

Dosage

Children: Refer to the specific formulation guidelines, as dosage will vary based on the active ingredient and formulation type.

Adults: Refer to the specific formulation guidelines, as dosage will vary based on the active ingredient and formulation type.

Mechanism of action

Croscarmellose sodium works by swelling and absorbing water when it comes into contact with gastrointestinal fluids. This swelling leads to the rapid disintegration of the tablet or capsule matrix, facilitating the release and absorption of the active pharmaceutical ingredients.

Pharmacodynamics

Croscarmellose sodium is classified as a superdisintegrant. Its ability to rapidly disintegrate solid dosage forms can significantly enhance the dissolution rate of the active ingredient, which is crucial for achieving therapeutic effects in a timely manner.

Pharmacokinetics

Croscarmellose sodium is not absorbed in the gastrointestinal tract and does not exert pharmacological effects in the body. It is considered non-toxic and is excreted unchanged. Its main role is as an excipient, influencing the formulation's characteristics rather than the pharmacokinetics of the active ingredients.

Precautions

• Use with caution in patients with known hypersensitivity to croscarmellose or its components.

Pregnancy

Safety in pregnancy has not been established. Use only if clearly needed.

Breast-feeding

Caution is advised when using during breastfeeding, as safety has not been established.

Storage

Store in a cool, dry place, away from moisture and heat.

Formulations

• Powder
• Granules

Indications

• Wound healing
• Skin ulceration
• Burns
• Psoriasis
• Dermatitis

Dosage

Children: Refer to the BNF for Children for appropriate dosing information based on the child's age and condition.

Adults: Refer to the BNF for specific formulations and dosing guidelines, as dosages may vary based on the condition being treated and the formulation used.

Mechanism of action

While there is no well-controlled data to formally substantiate the method of action, ongoing studies suggest that allantoin may induce a histological wound healing profile in animal models, leading to improved reestablishment of normal skin. This includes increased vasodilation, inflammatory cell presence, angiogenesis, fibroblast proliferation, and collagen deposition in treated wounds compared to untreated ones.

Pharmacodynamics

There is limited controlled data regarding the pharmacodynamic properties of allantoin. However, studies indicate that allantoin may possess moisturizing and keratolytic effects, increasing the extracellular matrix's water content and enhancing the desquamation of dead skin cells. These activities can promote cell proliferation and facilitate wound healing.

Pharmacokinetics

Specific pharmacokinetic data for allantoin in humans is limited. However, it is known to be applied topically, which suggests local absorption at the site of application. Systemic absorption is considered minimal due to its low molecular weight and hydrophilicity.

Pregnancy

There is limited data on the safety of allantoin in pregnancy. It is advisable to consult a healthcare professional before use.

Breast-feeding

Allantoin is generally considered safe during breastfeeding, but caution is recommended. Consult a healthcare professional before use.

Storage

Store at room temperature, away from direct sunlight and moisture. Keep out of reach of children.

Formulations

• Topical cream
• Gel
• Ointment

Indications

• HIV-1 infection
• HIV treatment-naive patients
• Patients with limited treatment options due to resistance

Mechanism of action

Lenacapavir inhibits HIV-1 replication by interfering with critical steps in the virus's lifecycle. It binds to the HIV-1 capsid protein, specifically to the phenylalanine-glycine binding pocket between the N-terminal and C-terminal domains of the capsid proteins. This binding disrupts the interaction of the capsid with essential host factors, such as CPSF6 and Nup153, which are necessary for the viral capsid's entry into the nucleus and subsequent integration of the viral genome into the host DNA. By preventing these interactions, lenacapavir effectively blocks viral uptake, assembly, and release, leading to reduced viral load in infected individuals.

Pharmacodynamics

Lenacapavir exhibits an extended pharmacokinetic profile that allows for prolonged antiviral activity. It has shown that single subcutaneous doses of 100 mg or more result in plasma concentrations that exceed the 95% effective concentration (EC95) for over 12 weeks, and doses of 300 mg or more maintain these levels for over 24 weeks. In treatment-naive HIV-1-infected patients, a single dose ranging from 20 mg to 450 mg has demonstrated significant reductions in plasma HIV-1 RNA levels by the ninth day post-injection, indicating robust antiviral efficacy.

Pharmacokinetics

Lenacapavir is administered subcutaneously, leading to systemic absorption with a long half-life that supports its extended dosing intervals. The pharmacokinetics are characterized by a prolonged duration of action, with significant plasma concentrations sustained for weeks after administration. Further details on its metabolism and excretion are not specified but are critical to understanding individual patient variability and potential drug interactions.

Pregnancy

There is insufficient data on the use of lenacapavir in pregnancy. It should only be used if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

It is unknown whether lenacapavir is excreted in human milk. Caution should be exercised when administering to nursing mothers.

Storage

Store in a refrigerator (2°C to 8°C). Do not freeze. Protect from light.

Formulations

• Subcutaneous injection

Dosage

Children: Refer to the BNF for Children for specific dosing guidelines in cases of methanol poisoning in pediatric patients.

Adults: In cases of methanol poisoning, immediate medical attention is required. Treatment typically involves the administration of fomepizole or ethanol as antidotes, along with supportive care and correction of metabolic acidosis. Dosing should be guided by clinical protocols.

Mechanism of action

Methanol is metabolized in the liver by alcohol dehydrogenase to formaldehyde, which is further oxidized to formic acid. Formic acid is responsible for many of the toxic effects of methanol, including metabolic acidosis and visual impairment. The severity of toxicity can depend on individual susceptibility and the activity of metabolic pathways, particularly those involving folic acid metabolism, which is necessary for formate metabolism.

Pharmacodynamics

Methanol toxicity manifests through its metabolic products, primarily formic acid, which decreases blood pH, leading to metabolic acidosis. This acidosis can cause complications such as respiratory distress and cardiovascular instability. The accumulation of formic acid also impacts mitochondrial function and can lead to cellular hypoxia and damage, particularly in the optic nerve, resulting in visual impairment or blindness.

Pharmacokinetics

Methanol is rapidly absorbed through the gastrointestinal tract and can cross the blood-brain barrier. It is metabolized primarily in the liver, with a significant portion converted to formaldehyde and then to formic acid. The elimination half-life of methanol varies and can be prolonged in cases of intoxication due to saturation of metabolic pathways. The time to peak concentrations can vary significantly; toxicity can develop long after initial ingestion, complicating management.

Adverse effects

• Metabolic acidosis
• Visual impairment
• Headaches
• Nausea
• Vomiting
• Dizziness
• Coma
• Death

Precautions

• Use with caution in individuals with liver impairment
• Monitor for signs of toxicity, especially in cases of suspected overdose

Pregnancy

Methanol is classified as a teratogen and should be avoided during pregnancy due to the risk of fetal toxicity and developmental harm.

Breast-feeding

Methanol is not recommended while breastfeeding due to potential harmful effects in the nursing infant.

Storage

Store in a cool, dry place away from light and heat. Keep container tightly closed and out of reach of children.

Indications

• Used as an excipient in tablet formulations
• Used as a bulking agent in capsule formulations
• Used in food products as a thickener or stabilizer

Dosage

Children: Refer to specific product guidelines as dosage will depend on the formulation and the active ingredients.

Adults: Refer to specific product guidelines as dosage will depend on the formulation and the active ingredients.

Mechanism of action

Microcrystalline cellulose acts as a non-digestible filler that enhances the flow properties of powders during the manufacturing of tablets and capsules. It does not have a direct pharmacological action on the body but ensures that the active ingredients are effectively delivered to the patient.

Pharmacodynamics

As a non-active ingredient, microcrystalline cellulose does not exert pharmacodynamic effects typical of active pharmaceutical ingredients. Its primary role is to provide a stable and consistent matrix for the drug, facilitating the release of the active compound once ingested.

Pharmacokinetics

Microcrystalline cellulose is not absorbed in the gastrointestinal tract; it passes through the digestive system largely unchanged. It adds bulk to the stool, which may aid in promoting regular bowel movements. The substance is excreted in feces, where it contributes to dietary fiber intake.

Pregnancy

Data regarding the use of microcrystalline cellulose during pregnancy is limited. It is advisable to consult with healthcare professionals before use.

Breast-feeding

Microcrystalline cellulose is considered safe during breastfeeding, as it is not absorbed systemically.

Storage

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

Indications

• Tablet coating
• Granule coating
• Improvement of drug stability
• Taste masking
• Aesthetic enhancement of pharmaceuticals

Dosage

Children: Dosage will depend on the specific formulation and active ingredients of the medication being coated. Refer to the specific product information for guidance.

Adults: Dosage will depend on the specific formulation and active ingredients of the medication being coated. Refer to the specific product information for guidance.

Mechanism of action

Opadry functions primarily as a coating polymer that adheres to the surface of tablets or granules, creating a protective layer. This layer can control the release of the active ingredient and protect it from environmental factors such as moisture and light. The specific composition of Opadry can vary, but it typically includes film-forming agents, plasticizers, and colorants that work together to achieve the desired coating characteristics.

Pharmacodynamics

The pharmacodynamics of Opadry is largely focused on its physical and chemical properties rather than specific biological interactions. The coating alters the dissolution characteristics of the drug, potentially leading to modified release profiles. This can enhance drug bioavailability or control the release rate of the active ingredient, thereby impacting the therapeutic effect.

Pharmacokinetics

As a coating agent, Opadry itself is not absorbed into the systemic circulation and does not have pharmacokinetic properties related to absorption, distribution, metabolism, or excretion of an active pharmaceutical ingredient. Its impact on pharmacokinetics is indirect, as it affects how the active drug is released and absorbed in the gastrointestinal tract.

Pregnancy

Opadry is a film-coating agent, and specific studies on its effects during pregnancy are not well-documented. Generally, it is advisable to use medications cautiously during pregnancy. Consult a healthcare provider for guidance.

Breast-feeding

Limited data are available regarding the safety of Opadry during breastfeeding. It is recommended to consult a healthcare provider before use.

Storage

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

Formulations

• Opadry OY - a coating system for oral solid dosage forms
• Opadry II - a polymer-based coating system for tablet and capsule applications

Indications

• Topical drug delivery
• Emulsifying agent in pharmaceutical formulations
• Stabilizing agent in aqueous solutions
• Controlled drug release systems

Dosage

Children: Refer to specific product guidelines for dosing, as it varies based on formulation and intended use.

Adults: Refer to specific product guidelines for dosing, as it varies based on formulation and intended use.

Mechanism of action

Poloxamer acts primarily by reducing the surface tension at the interface between different phases, such as oil and water. This property allows it to stabilize emulsions and improve the solubility of poorly soluble drugs. Additionally, poloxamer can form micelles in solution, encapsulating hydrophobic drugs and facilitating their delivery in the body.

Pharmacodynamics

Poloxamer exhibits surfactant properties that can enhance drug absorption and bioavailability by altering the permeability of biological membranes. Its action as a solubilizing agent can improve the pharmacological effects of drugs by ensuring they remain in a bioavailable form longer. The polymeric nature of poloxamer can also lead to sustained release of encapsulated drugs, prolonging their therapeutic effect.

Pharmacokinetics

Poloxamer is poorly absorbed when administered orally and is primarily excreted unchanged in the feces. Its absorption through the skin is minimal, making it more suitable for topical applications. The pharmacokinetics can vary based on the formulation and route of administration, with its action typically being localized rather than systemic.

Adverse effects

• Skin irritation
• Allergic reactions
• Gastrointestinal disturbances
• Headache

Precautions

• Use with caution in patients with known allergies to surfactants
• Assess for skin sensitivity before use
• Monitor for adverse reactions during therapy

Pregnancy

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

Breast-feeding

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

Storage

Store at room temperature, away from moisture and heat. Keep container tightly closed.

Formulations

• Poloxamer 188 (used as a surfactant in various formulations)
• Poloxamer 407 (used in pharmaceutical formulations and drug delivery systems)

Dosage

Children: Refer to specific drug formulations and product labels as purified substances can vary widely in their use and dosing.

Adults: Refer to specific drug formulations and product labels as purified substances can vary widely in their use and dosing.

Mechanism of action

The mechanism of action for purified compounds varies widely depending on the specific substance. Generally, purified drugs exert their effects by interacting with specific biological targets, such as receptors, enzymes, or ion channels, leading to a desired therapeutic effect. This interaction can involve binding to receptors to activate or inhibit signaling pathways, modulating enzymatic activity, or altering physiological processes.

Pharmacodynamics

Pharmacodynamics describes the effects of a drug on the body and the relationship between drug concentration and effect. For purified drugs, this can involve dose-response relationships and the time course of their action. The purified form often enhances potency and reduces variability in response among patients, which can lead to more predictable therapeutic outcomes. The overall effect is determined by the drug's affinity for its target, the efficacy of the drug-receptor interaction, and the downstream signaling pathways activated as a result of this interaction.

Pharmacokinetics

Pharmacokinetics involves the absorption, distribution, metabolism, and excretion (ADME) of a drug. For purified substances, absorption can be more efficient due to the absence of impurities that may affect solubility or stability. Distribution may also be enhanced, leading to higher bioavailability. Metabolism can be influenced by the structure of the purified compound, as it may be metabolized more readily by liver enzymes. Excretion typically occurs through the kidneys or liver, depending on the molecular characteristics of the purified drug.

Pregnancy

Consult with a healthcare professional, as the safety of purified forms of medications during pregnancy may vary depending on the specific substance.

Breast-feeding

Consult with a healthcare professional, as the safety of purified forms of medications during breastfeeding may vary depending on the specific substance.

Storage

Store in a cool, dry place, away from light and moisture, and keep out of reach of children.

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

There is no well controlled data that can formally substantiate the method of action. However, ongoing studies suggest that there may exist a histological wound healing profile induced by allantoin in rats that leads to the amelioration and fastening of the reestablishment of normal skin. This facilitation of wound healing is supported by observations that wounds inflicted to rat subjects to which topical allantoin preparations were applied histologically demonstrated increased vasodilation, presence of inflammatory exudates, number of inflammatory cells, angiogenesis, fibroblast proliferation, and increased collagen deposition when compared to rat subjects with wounds that did not receive any allantoin administration.

Pharmacodynamics

There is no well controlled and appropriate data that can formally substantiate the pharmacodynamic properties of allantoin. Nevertheless, ongoing studies suggest that allantoin possesses moisturizing and keratolytic effects, as well as abilities to increase the water content of the extracellular matrix and enhance the desquamation of upper layers of dead skin cells, all of which are activities that can promote cell proliferation and facilitate wound healing.

Mechanism of action

HIV-1 co-opts various host factors during its replicative cycle, including during host cell entry, nuclear integration, replication, and virion assembly. Following the initial fusion with the host cell membrane, the viral capsid is released into the host cell cytoplasm. The capsid comprises approximately 250 hexamers and exactly 12 pentamers, each composed of monomeric capsid proteins (CA). Each CA monomer has an N-terminal and C-terminal domain (NTD/CTD) and offers an interaction surface for host cell machinery. Several important protein-protein interaction interfaces occur between CA monomers in the assembled multimers; the binding constants of these proteins are substantially lower for assembled multimers than individual capsid monomers. To facilitate HIV-1 genomic integration, the capsid must cross the nuclear envelope, for which it utilizes the nuclear pore complex (NPC). Two host proteins shown to be essential for capsid nuclear entry that directly bind to the capsid are cleavage and polyadenylation specificity factor subunit 6 (CPSF6) and nucleoporin 153 (Nup153, an NPC protein present on the nucleoplasmic face of the complex). Both proteins bind the same phenylalanine-glycine binding pocket between the NTD and CTD of neighbouring CA monomers in multimeric CA assemblies. Lenacapavir contains a difluorobenzyl ring that occupies the same binding pocket as CPSF6/Nup153, overlapping with the benzyl group of F321 in CPSF6 and F1417 in Nup153 in the overlayed structures. Crystal structures of lenacapavir bound to CA hexamers reveal that six lenacapavir molecules bind to each hexamer, establishing extensive hydrophobic interactions, two cation-π interactions, and seven hydrogen bonds, contacting ~2,000 Ų of buried protein surface area. Strong binding of lenacapavir, therefore competitively interrupts capsid interactions with CPSF6 and Nup153. _In vitro_ HIV-1 replication inhibition experiments in a variety of cell lines show EC₅₀ values of ~12-314 pM, with greater efficacy against early steps over later steps. At very low concentrations (0.5 nM), lenacapavir inhibits viral nuclear entry, while at higher concentrations (5-50 nM), it additionally inhibits viral DNA synthesis and reverse transcription. As CPSF6 and Nup153 are essential for nuclear entry, it is likely that lenacapavir binding inhibits these interactions and blocks capsid nuclear entry. Lenacapavir may have additional effects beyond blocking interactions with host cell factors. Lenacapavir increases the rate and extent of CA assembly, dramatically extends the lifetime of assembled CA structures, even at high salt concentrations, and alters assembled capsid morphology. The stabilizing concentration is ~1:1, closely mimicking the observed binding stoichiometry to isolated CA hexamers. Further analysis suggests that lenacapavir binding alters intra- and inter-hexamer interactions, altering the structure and stability of the resulting assemblies. Serial passage of HIV-1 in increasing concentrations of lenacapavir resulted in the appearance of major resistance mutations Q67H and N74D, which remain sensitive to other antiretroviral drugs. Extended passage resulted in the additional mutations L56I, M66I, K70N, N74S, and T107N. All identified resistance mutations map to the lenacapavir binding site, and all but the Q67H variant show reduced replication capacity _in vitro_. Additional studies have shown no lenacapavir resistance in variants associated with resistance to other antiretrovirals or naturally occurring polymorphisms, suggesting a very low potential for cross-resistance in combination therapy.

Pharmacodynamics

Lenacapavir is an antiviral drug with an extended pharmacokinetic profile. Lenacapavir works against the HIV-1 virus by inhibiting viral replication: it interferes with a number of essential steps of the viral lifecycle, including viral uptake, assembly, and release. Single subcutaneous doses ≥100 mg in healthy volunteers resulted in plasma concentrations exceeding the 95% effective concentration (EC₉₅) for ≥12 weeks while doses ≥300 mg exceeded the EC₉₅ for ≥24 weeks. In treatment-naive HIV-1-infected patients, a single subcutaneous dose of 20-450 mg resulted in a mean maximum log₁₀-transformed reduction in plasma HIV-1 RNA of 1.35-2.20 by the ninth-day post-injection.

Mechanism of action

... The metabolic mechanisms of methanol toxicity /are/ reviewed. ... It is noted that the most severe toxicity occurs many hours following peak blood and tissue methanol concentrations so that these do not necessarily provide an accurate indication of toxicity. Individual differences are seen both in this latent period and in individual susceptibility to methanol. This susceptibility may depend on the activity of folic acid requiring metabolic reactions involved in formate metabolism, formate being an intermediate produced during methanol oxidation and responsible for many toxic effects of methanol. Studies of the characteristics of methanol poisoning in non-primates and monkeys are examined. Despite the ingestion of lethal doses of methanol, non-primates generally do not develop significant metabolic acidosis nor impairment of vision, and no consistent histopathology has been demonstrated in these species. In monkeys, results suggest that the latent period represents a period of compensated metabolic acidosis; when compensatory mechanisms are exhausted, blood pH begins to drop. Formate accumulates and produces acidosis in the methanol poisoned monkey, but not in the rat, apparently due to a slower rate of formate metabolism to carbon dioxide in the monkey. ... Studies demonstrating the role of alcohol dehydrogenase in methanol metabolism in the monkey are reported; however, the catalase/peroxidative system which participates in methanol metabolism in rats apparently does not function in the monkey. Formaldehyde and formate metabolism are also examined. The regulation of the rate of formate metabolism is governed by regulation of the hepatic tetrahydrofolate concentrations. ... Further research is needed to determine what step or process it is which places the primate at a distinct liability in the metabolic disposition of one carbon moieties. Methanol toxicity is observed in monkeys and humans but is not seen in rats or mice. The expression of methanol poisoning is related to the ability of an animal to metabolize formate to carbon dioxide. Since the rate of formate oxidation is related to hepatic tetrahydrofolate content and the activites of folate dependent enzymes, studies were designed to determine hepatic concentrations of hepatic tetrahydrofolate and activites of folate dependent enzymes of human liver and livers of species considered insensitive to methanol poisoning. An excellent correlation between hepatic tetrahydrofolate and maximal rates of formate oxidation has been observed. In human liver, levels were only 50% of those observed for rat liver and similar to those found in monkey liver. Total folate was also lower (60% decreased) in human liver than that found in rat or monkey liver. Interestingly, mouse liver contains much higher hepatic tetrahydrofolate and total folate than rat or monkey liver. This is consistent with higher formate oxidation rates in this species. A second important observation has been made. 10-Formyltetrahydrofolate dehydrogenase activity, the enzyme catalyzing the final step of formate oxidation to carbon dioxide, was markedly reduced in both monkey and human liver. Thus, two mechanisms may be operative in explaining low formate oxidation in species susceptible to methanol toxicity, low hepatic tetahydrofolate levels and reduced hepatic 10-formyltetrahydrofolate dehydrogenase activity. Formic acid, the toxic metabolite of methanol, has been hypothesized to produce retinal and optic nerve toxicity by disrupting mitochondrial energy production. It has been shown in vitro to inhibit the activity of cytochrome oxidase, a vital component of the mitochondrial electron transport chain involved in ATP synthesis. Inhibition occurs subsequent to the binding of formic acid to the ferric heme iron of cytochrome oxidase, and the apparent inhibition constant is between 5 and 30 mM. Concentrations of formate present in the blood and tissues of methanol-intoxicated humans, non-human primates and rodent m