Systemic reactions to ophthalmic drug preparations

The Efficacy of 2.5% Phenylephrine and Flurbiprofen Combined in Inducing and Maintaining Pupillary Dilatation during Cataract Surgery

Purpose

To evaluate the effectiveness of phenylephrine 2.5% and flurbiprofen 0.03% combined in inducing and maintaining mydriasis during extracapsular cataract extraction (ECCE).

Methods

One hundred patients undergoing ECCE + intraocular lens (IOL) implantation were randomly divided into four groups. The first group was given phenylphrine 10%, the second group phenylephrine 10% + flurbiprofen, the third group phenylephrine 2.5% and fourth group phenylephrine 2.5% + flurbiprofen. Cyclopentolate 1% was used in all patients. Phenylephrine and cyclopentolate were instilled preoperatively four times during 1 hour and flurbiprofen was given four times the day before surgery and twice with an hour's interval before operation. Pre-operative and post-cortex aspiration horizontal pupil diameters were measured with callipers viewed through the operating microscope.

Results

Pupil diameters in pre-operative and post-cortex aspiration were no different in the 2.5% and 10% phenylephrine groups (p>0.05). Both diameters were larger and pupillary constriction was smaller in the flurbiprofen groups (p<0.05).

Conclusions

2.5% phenylephrine was as effective as 10% phenylephrine, with and without flurbiprofen, in inducing and maintaining pupil dilatation during ECCE surgery.

Co-prescribing of topical and systemic beta-blockers in patients with glaucoma: a quality use of medicine issue in Australian practice

PURPOSE

Prescribing topical beta-blockers for patients with glaucoma, who are also being treated with systemic beta-blockers, raises efficacy and safety concerns. This potentially inappropriate co-prescribing practice is a Quality Use of Medicine issue. This study aimed to quantify the extent of co-prescribing of topical and systemic beta-blockers in Australian clinical practice.

METHODS

This is a retrospective analysis of de-identified billing data for supply (surrogate marker for prescribing) of topical and systemic beta-blockers from the Pharmaceutical Benefits Scheme (1999-2004) to concessional patients supplied either topical or systemic beta-blockers. The primary outcome was the percentage of patients supplied systemic beta-blockers within the patient population supplied topical beta-blockers. This percentage was calculated for each financial year (July 1999-June 2004), age group (<65 years; 65-74 years; 75-84 years; > or =85 years) and sex.

RESULTS

Approximately 20% of patients supplied topical beta-blockers (representing Australian glaucoma patients) were also supplied systemic beta-blockers, equating to more than 20 000 patients per year. This percentage varied with age, but not with year or sex. The percentage of patients co-supplied topical and systemic beta-blockers was the lowest (13%) for patients <65 years and the highest (23%) for patients 75-84 years.

CONCLUSIONS

Pharmaceutical Benefits Scheme supply data shows that the potentially inappropriate practice of co-prescribing topical and systemic beta-blockers affects more than 20 000 concessional patients in Australia each year, particularly the elderly. This Quality Use of Medicine issue has now been quantified; doctors, pharmacists and patients must be made aware of the reduced efficacy and potential for more side-effects from this co-prescribing practice.

Pharmacodynamics of a new ophthalmic mydriatic insert in healthy volunteers: potential alternative as drug delivery system prior to cataract surgery

Cataract surgery requires a satisfactory degree of mydriasis throughout the entire operation. A phase I, open-labelled, randomised, cross-over trial was conducted in 18 healthy volunteers to compare mydriasis obtained with subsequent administration of phenylephrine 10% and tropicamide 0.5% eyedrops or a new insoluble-matrix retropalpebral ophthalmic insert containing 5.38 mg phenylephrine and 0.28 mg tropicamide. Phenylephrine serum concentrations were measured over 6 hr following each treatment administration. Secondary end-points included cardiovascular, general and local tolerance and quantification of bacterial colonisation of the conjunctiva and the cultured insert, respectively. When normalized to the pupil diameter after conventional treatment, the diameter achieved with the insert was 1.13 (95% confidence interval, 0.94-1.48, P=0.38). Moreover, standard eye drops provided faster effective mydriasis than the insert, starting 30 min. as compared to 90 min. upon treatment administration (P<0.01, repeated-measures ANOVA). Phenylephrine concentrations remained almost undetectable for both treatments and no change in heart rate or blood pressure were observed throughout the study. Only three superficial punctuate keratitis were diagnosed with the insert and two with the eye drops. No significant bacterial contamination of conjunctiva swab and cultured insert was observed. The new insoluble-matrix retropalpebral ophthalmic mydriatic insert produced similar but delayed effective and prolonged mydriasis as compared to the standard delivery system. In addition to its potential usefulness in patients undergoing cataract surgery, such new ophthalmic delivery system may be an advantage in children who need to undergo fundus photography due to the single administration and excellent tolerance as well.

Systemic adverse effects of topical ocular treatments

Some eyedrops, gels or ointments may cause adverse effects as serious as those observed with systemic therapies. Because of their relatively poor penetration into eye tissue, ophthalmic drugs usually contain high concentrations of their active ingredient. Asking patients about these drugs to prevent interactions is useful when prescribing a new systemic treatment. Conversely, it is advisable to ask about ophthalmic drugs during the etiological investigation of possible iatrogenic effects.

Preventive effect of lacrimal occlusion on topical timolol-induced bronchoconstriction in asthmatics

AIM

To evaluate the potential preventive role of lacrimal occlusion on the topical timolol-induced bronchoconstriction in asthmatics.

METHODS

This was a prospective and single-masked study. Fourteen volunteer subjects with asthma were included. Collagen plugs were inserted into both canaliculi on one side to inhibit lacrimal drainage. The effect of lacrimal occlusion on lung function tests was measured before and 60 min after the instillation of a timolol drop in unplugged and plugged eyes. The spirometric measurements include forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, and mid expiratory flow-rate (FEF25-75).

RESULTS

The timolol (0.5%) drop administration into the eye caused a significant decrease in pulmonary functions in patients with asthma in whom the lacrimal punctae had not been occluded by collagen plug. P values were 0.008 for FVC and 0.001 for FEV1 and FEF25-75. The occlusion of the lacrimal duct by intracanalicular plugs significantly reduced this decrease in pulmonary function. P values were 0.6 for FVC, 0.8 for FEV1, and 0.5 for FEF25-75. The lacrimal occlusion did not affect heart rate and blood pressures. Three subjects complained of epiphora.

CONCLUSIONS

Lacrimal occlusion with intracanalicular collagen plugs may almost completely prevent the bronchoconstriction caused by topical timolol in asthmatics by inhibiting or decreasing systemic absorption of the medication.

Ocular adverse drug reactions

Drug-induced ocular side effects are described according to recent reports from the literature, the National Registry of Drug-Induced Ocular Side Effects, the World Health Organization (WHO) and the FDA. Adverse events are categorised as certain, probable/likely, possible, unlikely, conditional/unclassified and unassessable/unclassifiable where indicated. Ocular side effects of clinical importance are highlighted with guidelines for recognition, reporting and treatment of adverse drug reactions (ADRs). The current and future status of pharmacovigilance in ocular toxicology is addressed.

Cardiovascular considerations in using topical, oral, and intravenous drugs for the treatment of glaucoma and ocular hypertension: focus on beta-adrenergic blockade

Glaucoma and ocular hypertension are highly prevalent conditions in individuals over the age of 40 and are commonly seen together in patients with cardiovascular disease. Many of the antiglaucoma medications, when systemically absorbed, affect the sympathetic and parasympathetic nervous systems of patients and can cause cardiovascular toxicity. Such adverse effects are frequently associated with the long-term use of potentially toxic agents in elderly people, who are most prone to chronic eye disease. Moreover, patients may not associate their symptoms with the topical eye medications, and consequently may not report adverse drug effects. Drug-drug interactions can also occur when patients are taking medications for both cardiovascular disease and glaucoma. This review focuses on beta-adrenergic blockers as topical antiglaucoma medications and other topical antiglaucoma drugs. The systemic toxicity of these agents is reviewed, along with the possible drug interactions. Brief mention is also made of other antiglaucoma medications used alone and in combination with topical beta-blockers.

Bronchial responsiveness to beta-adrenergic stimulation and enhanced beta-blockade in asthma

OBJECTIVE

Beta-adrenergic blocking drugs have no effect on the airways of normal subjects but in asthma even small doses may cause severe deterioration. A seemingly obvious explanation for this abnormal sensitivity is that asthmatic airways, but not normal airways, are tonically dilated by the sympatho-adrenal system. However, studies suggest that sympatho-adrenal activity is normal in asthma, as is bronchial sensitivity to beta-agonists. The present study re-examines bronchial beta-adrenergic sensitivity in asthma and also measures antagonism produced in normal and asthmatic bronchi by a beta-blocking drug.

METHODOLOGY

The threshold bronchodilator doses of inhaled isoprenaline (dose required for a 35% increase in specific airway conductance 'PD35') was measured in 11 normal and 14 asthmatic adults on two separate occasions. After administering propranolol (inhaled or intravenously) PD35 was remeasured.

RESULTS

Sensitivity to isoprenaline was greater in symptomatic asthmatics (PD35 = 0.003 micromol) than in asymptomatic asthmatics (PD35 = 0.021 micromol) and in non-asthmatics (PD35 = 0.123 micromol; P < 0.001 in each case). Symptomatic asthmatics also showed 66-fold more antagonism than non-asthmatics when they were given propranolol by inhalation (P < 0.001) and sixfold more with intravenous propranolol (P = 0.005).

CONCLUSIONS

The increased sensitivity of asthmatics to inhaled isoprenaline suggests that they may also be more sensitive to their endogenous adrenaline, which may thus dilate and stabilize their airways. Taken with enhanced antagonism by propranolol, this provides insight into the aggravation of asthma by beta-blocking drugs.

Clindamycin, metronidazole, and chloramphenicol

Clindamycin, metronidazole, and chloramphenicol are three antimicrobial agents useful in the treatment of anaerobic infections. Clindamycin is effective in the treatment of most infections involving anaerobes and gram-positive cocci, but emerging resistance has become a problem in some clinical settings. Metronidazole is effective in the treatment of infections involving gram-negative anaerobes, but it is unreliable in the treatment of gram-positive anaerobic infections and is ineffective in treating aerobic infections. Additionally, metronidazole is often the drug of choice in treating infections in which Bacteroides fragilis is a serious concern. Chloramphenicol is effective in the treatment of a wide variety of bacterial infections, including serious anaerobic infections, but is rarely used in Western countries because of concerns about toxicity, including aplastic anemia and gray baby syndrome.

Allergic contact reactions due to phenylephrine hydrochloride in eyedrops

BACKGROUND

Dermatitis of and around the eye is common. Allergic contact reactions from phenylephrine are rare despite extensive use by ophthalmologists. Previous reports do not indicate crossreactivity between phenylephrine and other sympathomimetic drugs in patch testing.

METHODS

We report three cases of allergic contact reactions (dermato-conjunctivitis) after eyedrops. Skin prick tests, epicutaneous testing with the implicated drugs, additives, and a complete patch test battery, TRUE test (Upjohn-Pharmacia, Sweden), were performed in each patient.

RESULTS

All skin prick tests were negative. The three patients showed positive patch tests to phenylephrine and one of them also to ephedrine. Tolerance of the other eyedrops without phenylephrine was verified by challenge.

CONCLUSION

Phenylephrine was the responsible agent for the reactions in our patients as confirmed by clinical findings and positive patch tests. Our findings suggest the central structure as the sensitizing part of drug in the second patient. Patch testing is essential for diagnosis of allergic contact reactions of and around the eye.

A comparative study of the efficacy of 2.5% phenylephrine and 10% phenylephrine in pre-operative mydriasis for routine cataract surgery

It is common practice in many ophthalmic units to administer multiple applications of 10% phenylephrine in combination with an anti-cholinergic agent to ensure adequate pupil mydriasis prior to routine cataract surgery. Phenylephrine is a pure alpha-1 adrenoreceptor agonist known to produce marked systemic vasoconstriction and associated hypertension with occasional profound reflex bradycardia. Many reviews have suggested caution in the use of 10% phenylephrine in the elderly or hypertensive patient. In a prospective, randomised trial we have assessed pupil dilation comparing the efficacy of 10% phenylephrine (53 patients) versus 2.5% phenylephrine (62 patients). When administered in conjunction with 1% cyclopentolate four times over 1 hour pre-operatively, 2.5% phenylephrine was found to be as effective as 10% phenylephrine in the initiation and maintenance of mydriasis during both extracapsular and phacoemulsification cataract extraction.

Duration and long-term efficacy of phenylephrine-induced reduction in the systemic absorption of ophthalmic timolol in rabbits

Co-administration of phenylephrine decreases systemic timolol absorption after a single topical ocular dose of timolol in rabbits. This is probably due to vasoconstriction in the conjunctiva of the eye and nasal mucosa. In this study, we evaluated the duration of action and long-term efficacy of phenylephrine in reducing the systemic absorption of ophthalmic timolol in pigmented rabbits. Although co-administered phenylephrine had a short duration of interaction with systemic timolol absorption (20-60 min), its effect on systemic timolol absorption was substantial. The long-term vasoconstrictive effect of phenylephrine was studied by administering timolol-phenylephrine eyedrops into the eyes of rabbits once a day for two months. Systemic peak concentrations of timolol following timolol-phenylephrine eyedrop administration remained unchanged throughout the study. Phenylephrine may be useful additive in decreasing the systemic concentrations of ophthalmic drugs.

Ofloxacin compared with chloramphenicol in the management of external ocular infection

The safety and efficacy of 0.3% ofloxacin in treating bacterial ocular infections was compared with that of 0.5% chloramphenicol in a parallel-group, randomised clinical trial at five sites. Clinical and microbiological improvement rates were studied in 84 culture-positive patients. Patients with suspected bacterial ocular infections were evaluated for clinical improvement and were included in drug safety and comfort analyses. Clinical improvement did not differ significantly between drug treatments. All patients completing the study (79 assigned ofloxacin, and 74 chloramphenicol) showed clinical improvement. Clinical improvement in the culture-positive groups was 100% (41/41) after ofloxacin treatment, and 95% (41/43) after chloramphenicol treatment. Microbiological improvement rates were similar for the two drugs: 85% (33/39) improved with ofloxacin, and 88% (38/43) improved with chloramphenicol. Both drugs were well tolerated. Adverse reactions possibly due to the study medication occurred in 1% (1/89) of those who received ofloxacin, and in 4% (4/93) of those who received chloramphenicol.

Systemic morphine pharmacokinetics after ocular administration

Pharmacokinetics of a single dose of morphine ocularly applied is reported in rabbits before and after lacrimal canaliculi ligature. Our investigations are based on a sensitive reversed-phase ion-pair chromatographic determination of morphine. This study describes the various resorption sites of morphine when administered through the conjunctiva. After ocular administration, morphine rapidly reaches high blood levels compatible with pharmacological activity. Ocular bioavailability of morphine is higher than after non-parenteral routes. Canaliculi ligature modifies the morphine pharmacokinetic profile without significant modification of drug bioavailability. Our results suggest a great capacity of drug resorption for the conjunctiva, and indicate the major role of nasal mucosa in physiological conditions.

Chloramphenicol 4. Responsible topical use in ophthalmology

Chloramphenicol has gained widespread use in the topical treatment of ocular infections. The rationale for this use was based on the ability of chloramphenicol to penetrate the cornea and enter the anterior segment, together with its broad spectrum of antimicrobial activity. However, routine use in corneal ulceration or keratitis is not desirable. Hypopyon, when present, is usually sterile. Concerns about human exposure to chloramphenicol and its recent prohibition of use in food-producing animals, raise the need to review its indications and discuss alternatives. The role of chloramphenicol in ocular therapeutics is examined in this article.

Chloramphenicol 1. Hazards of use and the current regulatory environment

Chloramphenicol is a broad-spectrum antibiotic which has enjoyed extensive use in both medical and veterinary practice. Shortly after its introduction in the late 1940s, the use of chloramphenicol was associated with the induction of an idiosyncratic form of aplastic anaemia in man. This rare and unpredictable adverse effect has since been associated not only with systemic use but with topical applications, as well as occupational exposure. Recognition of the small risk of a potentially fatal adverse reaction, together with the risk of selection of chloramphenicol-resistant pathogens, has led to restrictions on the veterinary uses of chloramphenicol. In Australia at present, the use of chloramphenicol is only permitted in small animals. Its use is specifically prohibited in food-producing animals, including horses.