OTOPHEN COMBINATION PRODUCT EAR DROPS

Indications

• Reversal of hypotension from spinal or epidural anesthesia
• Reversible airways obstruction (e.g., asthma, bronchospasm)
• Nasal congestion

Dosage

Children: For children aged 1 month to 11 years, the dose is 1 mg/kg/hour by intravenous infusion, adjusted according to plasma-theophylline concentration. For children aged 12 to 17 years, administer 500–700 micrograms/kg/hour by intravenous infusion, also adjusted according to plasma-theophylline concentration.

Adults: For reversal of hypotension, administer 3–7.5 mg by slow intravenous injection every 3–4 minutes, adjusting according to response, with a maximum of 9 mg per dose. For airways obstruction, 30–60 mg may be given orally three times a day.

Mechanism of action

Ephedrine acts by stimulating adrenergic receptors, leading to bronchodilation and vasoconstriction. It increases the release of norepinephrine from sympathetic nerve endings, enhancing its action on alpha and beta-adrenergic receptors, which results in increased peripheral resistance and cardiac output.

Pharmacodynamics

Ephedrine exhibits both alpha- and beta-adrenergic activity. Its alpha-adrenergic effects lead to vasoconstriction, while beta-adrenergic stimulation results in bronchodilation. The drug also has a mild central nervous system stimulant effect, which can contribute to side effects such as anxiety and insomnia.

Pharmacokinetics

Ephedrine is well-absorbed from the gastrointestinal tract and is distributed widely throughout the body. It has a relatively long half-life due to its resistance to metabolism. The drug is primarily excreted unchanged in the urine. Its pharmacokinetic profile can be influenced by factors such as renal function and the presence of other medications that may affect its clearance.

Contra-indications

• Hypersensitivity to ephedrine or any of its components
• Severe hypertension
• Tachyarrhythmias
• Severe coronary artery disease
• Hyperthyroidism
• Prostatic hypertrophy

Adverse effects

• Anxiety
• Headache
• Insomnia
• Nausea
• Tremor
• Dry mouth
• Dizziness
• Cardiac arrhythmias
• Hypertension
• Urinary retention
• Myocardial infarction
• Psychotic disorders
• Pulmonary edema

Interactions

• Other sympathomimetics
• Xanthines (e.g., theophylline)
• Monoamine oxidase inhibitors
• Antihypertensive agents
• Antidepressants
• Corticosteroids

Precautions

• Use with caution in patients with diabetes mellitus
• Caution in elderly patients
• Hypertension
• Ischaemic heart disease
• Glaucoma (risk of angle-closure)
• Chronic obstructive pulmonary disease

Pregnancy

Manufacturer advises avoidance due to potential risks, including increased fetal heart rate.

Breast-feeding

Present in breast milk; manufacturer advises avoidance due to reported irritability and disturbed sleep in infants.

Storage

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

Formulations

• Oral suspension
• Oral solution
• Tablets (15 mg, 30 mg)
• Solution for injection (30 mg per 10 ml)

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

• Bronchial asthma
• Hypotension
• Nasal congestion
• Cardiac arrest

Dosage

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

Adults: Refer to the BNF for specific dosing guidelines based on the condition being treated.

Mechanism of action

Ephedrine acts by activating alpha-adrenergic and beta-adrenergic receptors. Directly, it stimulates these receptors, leading to vasoconstriction (alpha-1), increased cardiac chronotropy and inotropy (beta-1), and bronchodilation (beta-2). Indirectly, it inhibits norepinephrine reuptake and promotes the release of norepinephrine from nerve cells, resulting in prolonged sympathetic stimulation.

Pharmacodynamics

Ephedrine elevates blood pressure through increased heart rate and cardiac output, while also variably raising peripheral resistance. It induces bronchodilation through beta-adrenergic receptor activation in the lungs. Additionally, it enhances urine outflow resistance by stimulating alpha-adrenergic receptors in bladder smooth muscle. The therapeutic dose range is broad, with potential dosages from 5mg to 50mg, and caution is advised regarding the risk of hypertension and tachyphylaxis.

Pharmacokinetics

Ephedrine is rapidly absorbed and reaches peak plasma concentrations within 1 to 2 hours following oral administration. It is metabolized in the liver and excreted primarily via the kidneys. The duration of action is variable, but it generally lasts for 2 to 4 hours. Its pharmacokinetic profile can be influenced by individual patient characteristics, including renal function.

Adverse effects

• Tachycardia
• Hypertension
• Palpitations
• Nervousness
• Dizziness
• Nausea
• Vomiting

Interactions

• mianserin+ephedrine: Unknown (decreases effects)
• volatile halogenated anaesthetics+ephedrine: Unknown (additive effect)

Precautions

• Use with caution in patients with cardiovascular disorders
• Monitor blood pressure and heart rate during treatment
• Consider potential for tachyphylaxis with prolonged use

Pregnancy

Use only if clearly needed, as safety in pregnancy has not been established.

Breast-feeding

Caution is advised; ephedrine may pass into breast milk.

Storage

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

Formulations

• Oral tablets
• Injectable solution

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

Ephedrine is a direct and indirect sympathomimetic amine. As a direct effect, ephedrine activates alpha-adrenergic and beta-adrenergic receptors. As an indirect effect, it inhibits norepinephrine reuptake and increases the release of norepinephrine from vesicles in nerve cells. These actions combined lead to larger quantities of norepinephrine present in the synapse for more extended periods of time, increasing stimulation of the sympathetic nervous system. Ephedrine acts as an agonist of alpha-1, beta-1 and beta-2-adrenergic receptors. The stimulation of alpha-1-adrenergic receptors causes the constriction of veins and a rise in blood pressure, the stimulation of beta-1-adrenergic receptors increases cardiac chronotropy and inotropy, and the stimulation of beta-2-adrenergic receptors causes vasodilation and bronchodilation. Ephedrine alkaloids are members of a large family of sympathomimetic compounds that include dobutamine and amphetamine. Members of this family increase blood pressure and heart rate by binding to alpha- and beta-adrenergic receptors present in many parts of the body, including the heart and blood vessels. These compounds are called sympathomimetics because they mimic the effects of epinephrine and norepinephrine, which occur naturally in the human body. In addition to their direct pharmacological effects, many of these compounds also stimulate the release of norepinephrine from nerve endings. The release of norepinephrine further increases the sympathomimetic effects of these compounds, at least transiently. Ephedrine does not contain a catechol moiety, and it is effective after oral administration. The drug stimulates heart rate and cardiac output and variably increases peripheral resistance; as a result, ephedrine usually increases blood pressure. Stimulation of the alpha-adrenergic receptors of smooth muscle cells in the bladder base may increase the resistance to the outflow of urine. Activation of beta-adrenergic receptors in the lungs promotes bronchodilation. Ephedrine stimulates both alpha- and beta-adrenergic receptors. It is believed that beta-adrenergic effects result from stimulation of the production of cyclic adenosine 3',5'-monophosphate (AMP) by activation of the enzyme adenyl cyclase, whereas a-adrenergic effects result from inhibition of adenyl cyclase activity. In contrast to epinephrine, ephedrine also has an indirect effect by releasing norepinephrine from its storage sites. With prolonged use or if doses are given frequently, ephedrine may deplete norepinephrine stores in sympathetic nerve endings and tachyphylaxis may develop to the cardiac and pressor effects. Tachyphylaxis to the bronchial effects of the drug may also occur, but it is not the result of norepinephrine depletion.

Pharmacodynamics

Ephedrine increases blood pressure by stimulating heart rate and cardiac output and variably increasing peripheral resistance. It causes bronchodilation due to the activation of beta-adrenergic receptors in the lungs. By stimulating alpha-adrenergic receptors in bladder smooth muscle cells, ephedrine also increases the resistance to the outflow of urine. The therapeutic window of ephedrine is wide, as patients can be given doses of 5mg up to 50mg. Patients should be counselled regarding the pressor effects of sympathomimetic amines and the risk of tachyphylaxis. Also, the use of ephedrine for hypotension prophylaxis is associated with a higher risk of hypertension, compared to when ephedrine is used to treat hypotension.