Electropharmacological characterization of microminipigs as a laboratory animal using anti-influenza virus drug oseltamivir

Influenza associated cardiac arrhythmia- a systematic review

BACKGROUND

Influenza infection is rarely associated with cardiac conduction disorder. Cardiac arrhythmias due to such an infection have a full spectrum with ventricular arrythmias being the most common.

METHODS

In our systematic review from PubMed, OVID Medline and EMBASE we have identified 23 articles describing arrythmias associated with different influenza infection. Most of them were case reports where ventricular arrhythmias were the most common.

RESULTS

Complete heart block after influenza infection is usually temporary and a permanent pacemaker is rarely needed. There are reports of Influenza associated with arrhythmias in adults, neonates, and even fetuses in pregnant woman. Different mechanisms were described in literatures by which influenza causes arrhythmias such as interleukin 6 & tumor necrosis factor-alpha mediated inflammatory response, sympathetic overactivation, focal myocarditis and cleavage of angiotensin converting enzyme 2 protein which is cardioprotective.

CONCLUSIONS

ACE 2 binder influenza viruses have more prone to be associated with cardiac conduction disorder. Oseltamivir for influenza infection is also associated with bradycardia and can shorten or lengthen QT segment. Influenza vaccination has found to be protective from cardiac arrhythmia.

Oseltamivir-Associated Bradycardia in Critically Ill Patients

BACKGROUND

Oseltamivir is frequently administered to critically ill patients with presumed influenza. It may modulate Na⁺, K⁺, and Ca²⁺ channels to produce bradycardia.

OBJECTIVE

To evaluate the association between oseltamivir and bradycardia in critically ill patients and assess parameters associated with bradycardia.

METHODS

This was a retrospective audit of 203 critically ill adults with presumed influenza receiving at least 2 doses of oseltamivir. The primary outcome was the occurrence of bradycardia, defined as a heart rate (HR) ≤59 beats per minute (BPM) while receiving oseltamivir or a decrease of ≥20 BPM compared with the lowest HR before initiating oseltamivir.

RESULTS

A total of 88 (43.4%) patients manifested bradycardia, 59 with HR ≤59 BPM, 19 with HR decrease of ≥20 BPM, and 10 with both. The time from first dose to bradycardia was 51.4 ± 43 hours. In all, 48 (54.6%) patients received therapies for bradycardia, including increased inotropic/vasopressor dose, electrolyte replacement, electrocardiogram, discontinuation of other medications, cardiology consult, discontinuation of oseltamivir, and pacer placement. There were no significant differences between groups with bradycardia versus without in terms of demographics, laboratory values, hospital characteristics, or oseltamivir dosing. Multivariate logistic regression showed that bradycardia was associated with baseline HR, age, past medical history of neurological issues, and positive influenza status. Between hours 6 through 126, significant differences existed between groups in actual and lowest HR.

CONCLUSION AND RELEVANCE

Oseltamivir was associated with clinically relevant bradycardia in critically ill patients. Clinicians should closely monitor HR in critically ill patients receiving oseltamivir.

Characterization of microminipig as a laboratory animal for safety pharmacology study by analyzing fluvoxamine-induced cardiovascular and dermatological adverse reactions

Fluvoxamine is a selective serotonin-reuptake inhibitor, of which IC₅₀ values for serotonin- and noradrenaline-uptake process were reported to be 3.8 and 620 nmol/L, respectively, also known to directly inhibit cardiac Na⁺, Ca²⁺, and K⁺ channels. We characterized microminipig as a laboratory animal by analyzing fluvoxamine-induced cardiovascular and dermatological responses under halothane anesthesia. Fluvoxamine maleate was infused in doses of 0.1, 1, and 10 mg/kg over 10 min with a pause of 20 min (n = 4). The peak plasma concentrations were 35, 320, and 1906 ng/mL, of which free plasma concentrations were estimated as 20, 187, and 1108 nmol/L, respectively. The low and middle doses did not alter any cardiovascular variable. The high dose increased heart rate and mean blood pressure, prolonged QRS width, but shortened QT interval, whereas no significant change was detected in PR interval or QTcF. Moreover, it induced systemic erythema on the skin. Pretreatment of H₁/5-HT_2A antagonist cyproheptadine hydrochloride sesquihydrate in a dose of 0.3 mg/kg significantly attenuated the fluvoxamine-induced pressor response; but tended to further enhance sinus automaticity, atrioventricular nodal conduction; and ventricular repolarization in addition to intraventricular conduction delay; whereas it markedly suppressed onset of systemic erythema (n = 4). In microminipigs, cardiovascular adverse effects of the high dose may be manifested as a sum of its inhibitory action on the cardiac ionic channels and its stimulatory effects on serotonergic and adrenergic systems, whereas dermatologic reaction can be induced primarily through H₁/5-HT_2A receptor-dependent mechanism. Thus, microminipigs may be used for analyzing such multifarious adverse events of clinical serotonergic pharmacotherapy.

In vivo characterization of rate-dependent impact on the QT interval of microminipig assessed by atrial electrical pacing: Development of correction formulae of QT interval

Correction formulae of QT interval were developed for the halothane-anesthetized microminipigs by adopting atrial pacing (n=5), which were compared with Bazett's and Fridericia's formulae for humans, and Van de Water's one for dogs. The correction formulae: QTc=QT-0.2072 (RR-750) as linear and QTc=QT/(RR/750)^0.4007 as non-linear equations, were developed for microminipigs. These formulae can better correct the QT interval of the microminipigs compared with each of the conventional ones for humans and dogs. Moreover, analysis of the slope constant α values indicates that the rate-dependent change in the ventricular repolarization period of microminipig may better mimic that of humans than that of dogs.