AURONE FORTE

Indications

• Topical anesthesia for minor skin irritations
• Sore throat relief
• Dental procedures

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations.

Adults: Apply a thin layer to the affected area as needed, not exceeding the recommended frequency in product guidelines.

Mechanism of action

Benzocaine diffuses into nerve cells where it binds to sodium channels, preventing the channels from opening, and blocking the influx of sodium ions. Nerve cells unable to allow sodium into cells cannot depolarize and conduct nerve impulses. Benzocaine reversibly stabilizes the neuronal membrane, decreasing its permeability to sodium ions, thereby inhibiting depolarization of the neuronal membrane and blocking the initiation and conduction of nerve impulses.

Pharmacodynamics

Benzocaine is indicated for use as a topical anesthetic. It has a duration of action of approximately 10 minutes and a wide therapeutic window. Patients should be counselled regarding the risks of methemoglobinemia, a rare but serious condition that can occur with excessive use.

Pharmacokinetics

Benzocaine is poorly soluble in water, which limits its systemic absorption when applied topically. It is rapidly absorbed through the skin, and its effects are localized. The half-life and metabolism details are not extensively documented, but the drug is primarily metabolized in the liver. Clearance from the system generally occurs within a short time frame, correlating with its brief duration of action.

Adverse effects

• Methemoglobinemia
• Allergic reactions
• Local irritation
• Skin rash

Precautions

• Use with caution in patients with a history of methemoglobinemia
• Not for use on large areas of damaged skin or mucous membranes
• Avoid contact with eyes

Pregnancy

Benzocaine should be used in pregnancy only if the potential benefit justifies the potential risk to the fetus. Consult a healthcare professional.

Breast-feeding

Benzocaine is generally considered safe for use during breastfeeding, but caution is advised. Consult a healthcare professional for specific recommendations.

Storage

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

Formulations

• Topical cream
• Topical gel
• Topical ointment
• Lozenges

Indications

• Topical antiseptic
• Preservative in ophthalmic solutions
• Use in various pharmaceutical formulations

Dosage

Children: Refer to the BNF for Children for specific paediatric dosing recommendations, as chlorobutanol use may differ based on age and condition.

Adults: Refer to the BNF for specific adult dosing guidelines as chlorobutanol is used variably depending on formulation and indication.

Mechanism of action

Chlorobutanol acts as a detergent, disrupting the lipid structure of cell membranes which increases cell permeability, ultimately leading to cell lysis. It induces toxicity in conjunctival and corneal cells by causing cell retraction and cessation of normal cellular functions, including cytokine release, cell movement, and mitotic activity. Its mechanism also includes inhibition of oxygen utilization by the cornea, which can increase susceptibility to infections.

Pharmacodynamics

Chlorobutanol exhibits broad-spectrum antimicrobial activity as a detergent preservative. It has been shown in vitro to inhibit platelet aggregation through potentially unknown mechanisms, possibly involving the inhibition of the arachidonic acid pathway. This results in decreased thromboxane B2 formation, reduced cytosolic free calcium levels, and diminished ATP release. Additionally, chlorobutanol may have a negative inotropic effect on myocardial cells, affecting heart muscle contraction.

Pharmacokinetics

The pharmacokinetics of chlorobutanol are not thoroughly documented. However, being a detergent, it is expected to be absorbed and distributed in body tissues where it can exert its effects. The metabolism and excretion pathways are not well defined, necessitating further research to establish these parameters.

Adverse effects

• Conjunctival toxicity
• Corneal toxicity
• Cell retraction
• Cessation of normal cytokine activity
• Increased susceptibility to infection
• Platelet aggregation inhibition
• Myocardial negative inotropic effect

Precautions

• Use with caution in patients with compromised corneal integrity
• Monitor for signs of ocular toxicity
• Avoid exposure to sensitive tissues

Pregnancy

There is limited data on the safety of chlorobutanol during pregnancy; use only if clearly needed and the benefits outweigh the risks.

Breast-feeding

Caution is advised when administering chlorobutanol to breastfeeding mothers; consult a healthcare provider.

Storage

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

Formulations

• Topical solutions
• Ophthalmic preparations

Indications

• Pain relief
• Fever reduction
• Ear pain
• Testing drug metabolism

Dosage

Children: Refer to the BNF for Children for specific dosing guidance.

Adults: Refer to the BNF for specific dosing guidance.

Mechanism of action

Phenazone acts primarily in the central nervous system (CNS), increasing the pain threshold through the inhibition of cyclooxygenase enzymes, specifically COX-1, COX-2, and COX-3. This inhibition disrupts the synthesis of prostaglandins, which are mediators of pain and inflammation.

Pharmacodynamics

As an analgesic and antipyretic, phenazone serves to alleviate pain and reduce fever. It is frequently employed in pharmacological studies to assess the impact of other drugs or disease states on hepatic drug-metabolizing enzymes, demonstrating its importance in understanding drug interactions and metabolism.

Pharmacokinetics

Phenazone is absorbed well when administered orally. Its distribution in the body is extensive, and it is metabolized primarily in the liver, where it undergoes oxidation. The drug is excreted mainly through the kidneys. The elimination half-life can vary among individuals based on metabolic factors and liver function, necessitating caution in patients with hepatic impairment.

Adverse effects

• Nausea
• Vomiting
• Allergic reactions
• Skin rash
• Dizziness

Precautions

• Use with caution in patients with liver disease
• Monitor for signs of hypersensitivity

Pregnancy

Phenazone should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

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

Storage

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

Formulations

• Oral tablets
• Ear drops

Mechanism of action

Benzocaine diffuses into nerve cells where it binds to sodium channels, preventing the channels from opening, and blocking the influx of sodium ions. Nerve cells unable to allow sodium into cells cannot depolarize and conduct nerve impulses. Benzocaine reversibly stabilizes the neuronal membrane with decreases its permeability to sodium ions. Depolarization of the neuronal membrane is inhibited thereby blocking the initiation and conduction of nerve impulses.

Pharmacodynamics

Benzocaine is indicated for use as a topical anesthetic. It has a duration of action of approximately 10 minutes and a wide therapeutic window. Patients should be counselled regarding the risks of methemoglobinemia.

Mechanism of action

As a detergent, chlorobutanol disrupts the lipid structure of the cell membrane and increases the cell permeability, leading to cell lysis. It induces conjunctival and corneal cell toxicity via causing cell retraction and cessation of normal cytokines, cell movement, and mitotic activity. It disrupts the barrier and transport properties of the corneal epithelium as well as inhibits the utilization of oxygen by the cornea. Chlorobutanol also inhibits oxygen use by the cornea, which increases susceptibility to infection.

Pharmacodynamics

Chlorobutanol is a detergent preservative with a broad spectrum of antimicrobial activity. _In vitro_, chlorobutanol demonstrated to inhibit platelet aggregation and release via unknown mechanisms. A study proposes that the antiplatelet effect of chlorobutanol may occur from inhibition of the arachidonic acid pathway. It attenuated thromboxane B2 formation, elevation of cytosolic free calcium, and ATP release, and additionally exhibited a significant inhibitory activity toward several aggregation inducers in a time- and concentration-dependent manner. Chlorobutanol may exert a direct negative inotropic effect on myocardial cells to isometric tension produced by the heart. Chlorobutanol was shown to induce conjunctival and corneal cell toxicity _in vitro_: at a concentration of 0.1%, Cbl caused near depletion of the squamous layer while degeneration of corneal epithelial cells, generation of conspicuous membranous blebs, cytoplasmic swelling, and occasional breaks in the external cell membrane were observed at a concentration of 0.5%.

Mechanism of action

Antipyrine is thought to act primarily in the CNS, increasing the pain threshold by inhibiting both isoforms of cyclooxygenase, COX-1, COX-2, and COX-3 enzymes involved in prostaglandin (PG) synthesis.

Pharmacodynamics

Antipyrine is an analgesic and antipyretic that has been given by mouth and as ear drops. Antipyrine is often used in testing the effects of other drugs or diseases on drug-metabolizing enzymes in the liver. (From Martindale, The Extra Pharmacopoeia, 30th ed, p29)