Tetracaine hydrochloride eye drops with local anesthetic effectDear Colleagues, this week we will examine together an ophthalmic preparation used topically when a very short-acting local anesthetic effect is desired. I have selected this formula as the formula of the week, which I believe will particularly draw the attention of hospital pharmacists.Rp.
Tetracain hydrochloridum 0.05 g
Solutio pH 6,5 cum phenylhydrargyri borate ad. 10.00 ml
Ingredients in the formula;
Tetracaine chloride- Amethocaine hydrochloride- Tetracainii chloridum- Tetracaini hydrochloridum [Ph. Eur.3; Ph.Int.III];Tetracaine hydrochloride is a white, odorless, slightly hygroscopic crystalline powder. It is freely or very soluble in water; soluble in alcohol; slightly soluble in chloroform; practically insoluble in ether. The British Pharmacopoeia (BP) has reported the pH of its 1% solution as 4.5-5.5. Tetracaine is an ester-type, long-acting local anesthetic. It is considered the most toxic local anesthetic drug compared to other local anesthetics. It is available in various injectable forms for spinal anesthesia and preparations suitable for topical use. These preparations are typically used prior to examinations of the larynx, trachea, or esophagus to prevent laryngeal and esophageal reflexes and for local analgesia. Additionally, it can be used for the palliative relief of pain caused by Herpes labialis. Like other local anesthetics, tetracaine inhibits the generation and conduction of nerve impulses across the cell membrane. They block impulse conduction in excitable membranes by preventing the transient increase in permeability.
When its topical and aerosol solutions are used, its effect begins in 3-10 minutes and lasts for 30-60 minutes. In ophthalmic preparations, the effect begins in 15 minutes and lasts for approximately 15 minutes. Tetracaine hydrochloride should be stored at room temperature below 30°C in tightly closed, airtight containers. It must be protected from light. Aqueous solutions should be discarded if crystallization, discoloration, or cloudiness is observed.Phenylmercuric borate;Phenylmercuric borate is an organomercury compound with antibacterial and antifungal properties used as an antiseptic. It is primarily bacteriostatic, but also exhibits a slow bactericidal effect. Its activity has been reported to be pH-dependent. Like other phenylmercury compounds, it is included as a preservative in cosmetic, ophthalmic, and pharmaceutical preparations. For antiseptic action, it is applied to the skin and mucous membranes as a tincture (alcoholic solution) or ointment at a concentration of 0.001-0.1%.Preparation of the formula;The calculated amount of Tetracaine is dissolved in 10 ml of Phenylmercuric borate solution. It is filtered through a membrane filter using sterile filtration methods into a sterile eye drop bottle under aseptic conditions.Phenylmercuric borate solution with pH 6.5;
Rp
Acidum boricum 15.457 g
Natrii boras 0.589 g
Phenylhydrargyri boras 0.050 g
Aqua pro injectione ad 1000.000 ml
Preparation;200 ml of distilled water for injection is boiled and phenylmercuric borate is dissolved in it. Boric acid and medicinal borax are added to it and dissolved with heat. It is brought to the specified volume with water for injection. It is filtered through a glass filter with a maximum pore size of 20-40 µm, distributed into 20 ml ampoules, and sterilized. It is used as a solvent in eye drop preparations. It is incompatible with bromides, iodides, chlorides, sulfides, and certain sulfur derivatives.TETRACAINE HYDROCHLORIDE EYE DROPS; It should not be used without medical supervision. It should not be prescribed for the patient’s self-administration. It is contraindicated in patients known to be hypersensitive to tetracaine or any of its components.
Prolonged use of a topical ocular anesthetic may result in a decrease in the duration of effect; therefore, increasingly more medication may be required to achieve the desired anesthetic effect, and wound healing may be delayed. Such prolonged use may lead to corneal epithelial erosions followed by corneal infection and/or corneal opacification with permanent vision loss, or corneal perforation.
During anesthesia, it is crucial to protect the eye from irritating chemicals, foreign bodies, and rubbing. Patients should be warned not to touch or rub their eyes until the anesthetic effect wears off.
Systemic toxicity with topical ophthalmic use of local anesthetics is quite rare. For a simple topical examination, 1 or 2 drops are instilled prior to the procedure. More drops may be added as needed.
For minor surgical procedures such as foreign body removal or suture removal, 1 or 2 drops are instilled 1 to 3 times, every 10 or 15 minutes.
For prolonged anesthesia, such as in cataract extraction, 1 or 2 drops are used 3 to 5 times, every 10 to 15 minutes. The effect of topically applied anesthesia usually begins in 15 minutes and lasts for 15 minutes.
Wishing you a good week…
References:
1- TEB Formulary.
2- RxMediaPharma®2016 Interactive Drug Information Source.
Spec. Pharm. Ahmet Nezihi Pekcan
Pekcan Pharmacy – Konya
[email protected]
Tel: (332) 3520657http://www.majistralformul.com/
