Distribution of propranolol in periocular tissues: a comparison of topical and systemic administration

To compare intralesional and oral propranolol for treating periorbital and eyelid capillary hemangiomas

Purpose:

A pilot randomized control trial to compare the efficacy and side effects of intralesional and oral propranolol in periorbital and eyelid capillary hemangiomas.

Methods:

Twenty patients were prospectively randomized to two groups of ten each. Group 1 was initiated on oral propranolol 1 mg/kg/day titrated to final dose of 3 mg/kg/day over 1 week which was continued for 6 months and then tapered over 1 week; Group 2 received 3 doses of direct intralesional propranolol hydrochloride 1 mg/ml; 0.2 ml/cm 4–6 weeks apart. Hemangioma area and corneal astigmatism were measured.

Results:

Within each group at 6 months there was a significant reduction in area (group 1: 83.48 ± 11.67%, P = 0.0019; group 2: 67.78 ± 21.71%, P = 0.0019) and improvement in astigmatism (pre, post: group 1: 2.98D @ 179.8°, 1.13D @ 179.8°, P = 0.0045; group 2: 1.62D @ 90.16°, 0.75D @ 179.9°, P = 0.0001). There was no difference in area reduction (P = 0.056), change in appearance (P = 0.085), ptosis (P = 0.23) and side effects (lethargy, poor feeding; P = 0.171) between the two groups.

Conclusion:

Efficacy and side effects with intralesional propranolol are comparable to oral propranolol for periorbital and eyelid lesions.

Ocular Safety of Intravitreal Propranolol and Its Efficacy in Attenuation of Choroidal Neovascularization

PURPOSE

Determine the safe dose of intravitreal propranolol (IVP), and evaluate its inhibitory effect on laser-induced choroidal neovascularization (CNV).

METHODS

To determine the IVP safe dose, 32 rabbits were divided into 4 groups. Three of these groups received IVP (15 μL) corresponding to 15 μg (group B), 30 μg (group C), and 60 μg (group D). The control group (A) received 15 μL saline. Safety was assessed by ocular examination, electroretinography (ERG), routine histopathologic evaluation, immunohistochemistry for glial fibrillary acidic protein (GFAP), and real-time qPCR for GFAP, VEGF, thrombospondin 1 (TSP1), and pigment epithelium-derived factor (PEDF). A similar experiment was performed in 24 mice by using a 100-fold lower amount of propranolol (0.15, 0.3, and 0.6 μg in 2 μL) based on vitreous volume. For assessment of the angioinhibitory effects of IVP, CNV was induced in 42 mice via laser burns. Mice were divided into two groups: group 1 received the safe dose of IVP (0.3 μg in 2 μL) and group 2 received saline. Neovascularization area was quantified by intercellular adhesion molecule (ICAM)-2 immunostaining of choroidal-scleral flat mounts by using ImageJ software.

RESULTS

According to clinical, ERG, and histopathologic findings, 30 μg IVP was chosen as the safe dose in rabbit eyes, comparable to 0.3 μg IVP in mouse eyes. As compared to the control eyes, the development of CNV was attenuated (4.8-fold) in mice receiving 0.3 μg IVP.

CONCLUSIONS

Intravitreal propranolol injection up to the final dose of 30 μg in rabbits and 0.3 μg in mice was safe, and was effective in attenuation of CNV in mice.

Pharmacokinetics and local safety profile of propranolol eye drops in rabbits

BACKGROUND

Oral propranolol, a nonselective β-blocker, is able to reduce the progression of retinopathy of prematurity in newborns, but it appeared unsafe. This study aimed to find, in rabbits, a propranolol eye drop concentration able to induce lower plasma but higher retinal concentrations than those obtained after oral administration.

METHODS

Male New Zealand white rabbits were treated with oral propranolol (0.25 mg/kg/6 h) for 5 d, and propranolol concentrations were measured after 1, 2, 3, and 6 h in plasma, aqueous humor, vitreous humor, and retina. These concentrations were compared with those obtained after the administration of one drop of 25 μl of propranolol 0.1% prepared in saline, applied every 6 h to both eyes for 5 d. A Draize eye test and histological analyses were performed to assess eye drop tolerability.

RESULTS

The administration of eye drops produced retinal concentrations similar to, but plasma concentrations significantly lower than, those measured after oral administration. The local tolerability profile was excellent.

CONCLUSION

Propranolol eye drops are able to ensure high retinal and low plasma concentrations of propranolol, and this finding opens the perspective of possible topical treatment with propranolol in newborns with retinopathy of prematurity.

Effects of dosing protocol on distribution of propranolol in periocular tissues after topical ocular instillation

PURPOSE

Our previous study demonstrated that topical ocular instillation can deliver effective concentrations of propranolol in the periocular tissues, and may be superior to oral propranolol in the treatment of periocular capillary hemangiomas. The objective of this study was to investigate the effects of dosing protocol on the distribution of propranolol in the periocular tissues and plasma after topical ocular instillation.

METHODS

Each rabbit received propranolol 0.5% ophthalmic solution using one of the following dosing protocols: three drops of 50 μL, one drop of 50 μL, or one drop of 25 μL. The periocular tissues (e.g. eyelids and extraocular muscles) and blood were collected and assayed for propranolol at 1 h after dosing.

RESULTS

Decreasing the concentration of eye drops (1% to 0.5%), decreasing the number of eye drops during dosing (three drops to one drop), or decreasing the instilled volume (50 µL to 25 µL) generally lowered the concentration of propranolol in the periocular tissues. Nevertheless, therapeutic levels of propranolol (> 0.4 μg/g) were delivered to the periocular tissues at 1 h after dosing using any of the three protocols examined. Dose-dependent concentrations in some periocular tissues and plasma were observed over the dose range of 0.125 mg to 1.5 mg. The plasma concentration of propranolol was not measurable when a single 25 μL of propranolol 0.5% was instilled in the eye.

CONCLUSIONS

The dosing protocol of topical ocular instillation can be tailored to achieve the desired therapeutic concentrations of propranolol in the periocular tissues while minimizing systemic exposure.

The effect of β receptor blockade through propranolol on corneal neovascularization

PURPOSE

To evaluate the inhibitory effects of propranolol, a nonselective and lipophilic β-adrenergic receptor blocker, on alkali-induced corneal neovascularization (NV).

METHODS

Corneal NV was induced in 24 eyes of 24 Wistar rats using NaOH. Following alkali burn, animals were randomized into 4 groups according to topical treatment. Group I received 0.9% NaCl, Group II received preservative-free dexamethasone sodium phosphate 1 mg/mL, Group III received propranolol hydrochloride 1 mg/mL, and Group IV received 0.5 mg/mL propranolol hydrochloride drops twice a day for 7 days. The inhibitory effects of the drugs were compared as the percent areas of cornea covered by NV. Anti-vascular endothelial growth factor (VEGF) and anti-active caspase-3 immunostainings were also performed in corneal sections.

RESULTS

The median percent area of corneal NV was 59% (40.3-65.6) in Group I, 25.5% (20.9-43.4) in Group II, 68.9% (36.7-78.0) in Group III, and 50.4% (42.2-63.3) in Group IV. Group III and IV did not show any difference in comparison to Group I. Group II showed a statistically significant smaller area of corneal NV compared with Group I, III, and IV (P=0.004 for each comparison). Anti-VEGF immunostaining was significantly less in Group II compared with the other groups. Anti-active caspase-3 immunostaining was not different among the treatment groups.

CONCLUSIONS

Topical propranolol 1 or 0.5 mg/mL does not have a significant inhibitory effect on alkali-induced corneal NV in rats.

Understanding the pharmacokinetics of anxiolytic drugs

INTRODUCTION

Anxiety disorders are considered the most common mental disorders and they can increase the risk for comorbid mood and substance use disorders, significantly contributing to the global burden of disease. For this reason, anxiolytics are the most prescribed psychoactive drugs, particularly in the Western world.

AREAS COVERED

This review aims to analyze pharmacokinetic profile, plasma level variations so as the metabolism, interactions and possible relation to clinical effect of several drugs which are used primarily as anxiolytics. The drugs analyzed include benzodiazepines, anticonvulsants (pregabalin, gabapentin), buspirone, β-blockers and antihistamines (hydroxyzine). Regarding the most frequently used anxiolytic benzodiazepines, data on alprazolam, bromazepam, chlordesmethyldiazepam, chlordiazepoxide, clotiazepam, diazepam, etizolam, lorazepam, oxazepam, prazepam and clonazepam have been detailed.

EXPERT OPINION

There is a need for a more balanced assessment of the benefits and risks associated with benzodiazepine use, particularly considering pharmacokinetic profile of the drugs to ensure that patients, who would truly benefit from these agents, are not denied appropriate treatment. An optimal pharmacological approach involving an integrative pharmacokinetic and pharmacodynamic optimization strategy would ensure better treatment and personalization of anxiety disorders. So it would be desirable for the development of new anxiolytic drug(s) that are more selective, fast acting and free from the unwanted effects associated with the traditional benzodiazepines as tolerance or dependence.