Resolution of hyphaema following intracameral injection of tenecteplase in a Stock Horse

Use of recombinant tissue plasminogen activator (rTPA) for treatment of fibrin in the anterior chamber of the horse

BACKGROUND

Recombinant intracameral tissue plasminogen activator (rTPA) administration can aid clearance of fibrin from the anterior chamber.

MATERIALS AND METHODS

In this retrospective multicentre case series, the effect of intracameral rTPA administration to treat fibrin in the anterior chamber resulting from trauma or inflammatory ocular disease was evaluated. Clinical data from 30 treatments in 29 horses were obtained from medical records from 2003 to 2022. Association between time from onset of clinical signs and time for rTPA treatment to effect was studied with regression analysis.

RESULTS

Twenty-seven horses (93.1%) had no previous history of ophthalmic disease; one had an iridic cyst, and another had equine recurrent uveitis. The majority of cases were related to trauma (79.3%). Median time from the onset of clinical signs to treatment was 12 h (IQR = 4-48 h). rTPA (72% 20 µg; 24% 25 µg; 3.3% 40 µg) was administered once in all but one eye, which was treated twice. Resolution of fibrin was seen in 96.9% (29/30) of treatments. Fibrin accumulation recurred in one case but resolved 14 days after the second treatment. Complications were seen in four treatments (13.3%): moderate pain for 24 h, intracameral debris and mild intracameral haemorrhage in a horse that received 40 µg of tissue plasminogen activator. Recurrence of fibrin accumulation was absent in 96.7% of cases. Median time to effect was 20 min (IQR = 10-45 min). Time for rTPA treatment to effect was not associated with time from fibrin formation (R2 = 0.09; p = 0.11).

CONCLUSION

Intracameral rTPA treatment can be considered at 20-25 µg in 0.1 mL solution to aid resolution of fibrin accumulation.

Intracameral tenecteplase during phacoemulsification in rabbits: clinical assessment of the anterior segment and biochemical analysis of the aqueous humor

Abstract To evaluate the use of tenecteplase in transoperative phacoemulsification in healthy rabbits, the study was carried out with fifteen New Zealand rabbits, divided into three groups: control group (CG), untreated group (UG) and treated group (TG). UG and TG were operated by phacoemulsification and TG received 50 µg / 0.3 mL of intracameral tenecteplase. The postoperative evaluations were 24 h, 72 h, 7 days, 15 days and 21 days. In TP21 the animals were submitted to euthanasia and aqueous humor samples were collected. No significant differences were observed in the clinical evaluations between CG and TG in relation to incidence rates of intraocular pressure (IOP), corneal edema, fibrin deposits, hyphema, aqueous flare and synechia. In the physicochemical evaluation of the aqueous humor, there were no significant differences between the three groups in relation to pH values and concentrations of chloride ions. The aqueous humor density values were statistically different between CG and the other groups. In the histological evaluation, there were no significant differences between the groups. The use of tenecteplase in transoperative phacoemulsification in rabbits did not present significant differences in terms of clinical, physicochemical and histological parameters.

Pharmacokinetics and thrombolytic effects of the recombinant tissue-type plasminogen activator in horses

Background

To test the efficacy of the recombinant tissue-type plasminogen activator (rt-PA) alteplase in horses, the thrombolytic effect was tested in in vitro generated equine thrombi. The extent of lysis was determined by measuring the decrease in thrombi weight over a period of 4 hours. In vivo pharmacokinetics of alteplase were determined in 6 healthy horses. A single dose (1 mg/kg) was applied via intravenous infusion over a period of 30 minutes Coagulation-related variables, blood count and clinical parameters were taken before the treatment and until 48 h after treatment. In addition, plasma rt-PA concentration was measured until 300 min after commencing the infusion.

Results

In vitro, a dose dependent decrease of thrombus weight ranging from a 56 (± 6.5) % decrease for 0.5 μg/ml to 92 (± 2.1) % decrease for 5 μg/ml rt-PA was noted. The D-dimer concentration in the lysis medium correspondingly increased from 0.10 up to 10.8 mg/l.

In vivo, none of the horses showed an adverse reaction to the alteplase infusion. In some horses blood parameters were slightly altered. The 1 mg/kg dose yielded the following pharmacokinetic parameters: Cmax = 1.25 ± 0.27 μg/ml; CL = 21.46 ± 5.67 ml/min/kg; dominant half life (t1/2α) = 6.81 ± 1.48 minutes; median elimination half life (t1/2β) = 171 min (range: 85–1061); AUC = 50.33 ± 17.62 μg · min /ml.

Conclusion

These findings indicate that a single dose of 1 mg/kg alteplase results in rt-PA plasma concentrations comparable to those in humans and might be sufficient for a thrombolytic therapy in horses. Further studies must be performed to determine the alteplase effectiveness in horses with jugular vein thrombosis.