REMDESIVIR (VEKLURY) FOR TREATING COVID-19 PATIENTS: WHAT TO EXPECT FROM A CARDIAC ELECTROPHYSIOLOGICAL PERSPECTIVE

BACKGROUND

Remdesivir was authorized with conditions in Canada on July 27, 2020 for the treatment of severe COVID-19 in adults and youth (aged ≥ 12 years) with pneumonia requiring supplemental oxygen. In the Canadian Veklury® monograph, it is mentioned that current non-clinical and clinical data do not suggest a risk of QT prolongation, but QT prolongation has not been fully evaluated in humans. Interestingly, in a recent small series of 67 patients treated with remdesivir alone daily (200 mg Day 1, 100 mg Days 2-7); although no instance of torsades de pointes was reported, there was a mean 24.4-ms increase in the QTc, with 9% of all QTc ≥ 500 ms and 9% of all DQTc ≥ 60 ms. Our aim was therefore to further evaluate the effects of remdesivir on cardiac electrophysiology.

METHODS AND RESULTS

1) Ex vivo Langendorff retroperfusion experiments: Isolated hearts from male Hartley guinea pigs were either let at their natural sinus rhythm (SR) or paced at basic cycle lengths (BCL) of 250 or 200 ms. They were allowed to stabilize and were then exposed for 15 minutes to either remdesivir 3 (n=7), 10 (n=7) or 30 (n=5) µmol/L to assess drug-induced effect on monophasic action potential duration measured at 90% repolarization (MAPD90). 2) In vivo wireless cardiac telemetry experiments: Guinea pigs (n=3) implanted with radio transmitters were administered i.p. daily doses of remdesivir (5 mg/kg on Day 1 and 2.5 mg/kg on Days 2-10) and continuous ECG recordings were made. Results: See Tables.

CONCLUSION

Previous clinical studies have shown peak plasma concentrations of remdesivir in the 5-10 µmol/L range after the 200 mg Day 1 dose. In the present study, remdesivir had hardly any significant ex vivo effect on MAPD90 at clinically relevant concentrations (3-30 µmol/L). However, in vivo, the drug caused significant prolongation of the QT at Day 1 and Day 10 and of QTcF at Day 10. Interestingly, a trend toward bradycardia was observed in vivo after each administration of remdesivir. More in vivo experiments are therefore required to rule out any QTc-prolonging effects of remdesivir at clinically recommended dosage.

Pimozide (Orap) prolongs cardiac repolarization by blocking the rapid component of the delayed rectifier potassium current in native cardiac myocytes

BACKGROUND

Several cases of QT prolongation and ventricular tachyarrhythmia have been reported with pimozide, a potent neuroleptic useful in the management of motor and phonic tics associated with Tourette syndrome. To further elucidate the mechanism underlying these clinical observations, the effects of pimozide on monophasic action potential duration (MAPD(90)) and on potassium currents involved in the repolarization of native isolated ventricular myocytes were examined.

METHODS AND RESULTS

Studies were undertaken in eight isolated guinea pig hearts that demonstrated reverse rate-dependent prolongation of cardiac repolarization by pimozide 100 nmol/L. Action potential duration increased 24% from baseline 115 +/- 2 to 142 +/- 4 msec with pimozide 100 nmol/L during pacing at 250 msec cycle length, while a 10% increase from 97 +/- 2 to 107 +/- 3 msec was seen with pacing at a cycle length of 150 msec. Experiments in native isolated ventricular myocytes (n = 20) demonstrated concentration-dependent block of the rapid component (I(Kr)) of the delayed rectifier potassium current: tail current was decreased by 50% at 15 nmol/L.

CONCLUSIONS

Pimozide possesses cardiac electrophysiological effects similar to those of class III antiarrhythmic drugs. These effects are concentration-dependent and observed at recommended dosages of the drug. Since pimozide is strongly metabolized by CYP3A4, special care should be taken to avoid potential pharmacokinetic interactions leading to high plasma levels of pimozide and proarrhythmia.

Domperidone should not be considered a no-risk alternative to cisapride in the treatment of gastrointestinal motility disorders

BACKGROUND

Several cases of QT prolongation and ventricular tachyarrhythmia have been reported with domperidone, a gastrokinetic and antiemetic agent available worldwide but still under investigation in the United States. Although electrolyte disturbances such as hypokalemia could account for some of these events, we hypothesized that domperidone may have unsuspected electrophysiological effects predisposing some patients to proarrhythmia.

METHODS AND RESULTS

Studies were undertaken in 9 isolated guinea pig hearts, which demonstrated reverse use-dependent prolongation of cardiac repolarization by 100 nmol/L domperidone. Action potential duration increased 27% from baseline with domperidone (from 114+/-3 to 145+/-2 ms) during pacing at a cycle length of 250 ms, and a 9% increase (from 97+/-2 to 106+/-3 ms) was seen with pacing at a cycle length of 150 ms. Experiments in human ether-a-go-go-related gene (HERG)-transfected Chinese hamster ovary cells (n=32) demonstrated a concentration-dependent block of the rapid component (I(Kr)) of the delayed rectifier potassium current. The tail current decreased by 50% at 162 nmol/L domperidone.

CONCLUSIONS

Domperidone possesses cardiac electrophysiological effects similar to those of cisapride and class III antiarrhythmic drugs. These effects are observed at clinically relevant concentrations of the drug. Therefore, domperidone should not be considered a no-risk alternative to cisapride, a drug that was recently withdrawn from the US market.

Vitamin K modulates cardiac action potential by blocking sodium and potassium ion channels

BACKGROUND

Cardiovascular collapses, syncopes, and sudden deaths have been observed following the rapid administration of intravenous vitamin K. Our objectives were to characterize the effects of vitamin K on cardiac action potentials and to evaluate effects of vitamin K on sodium and potassium currents, namely I(Na), I(Kr), and I(Ks).

METHODS AND RESULTS

Guinea pig hearts (n = 21) were paced at a cycle length of 250 msec and exposed to vitamin K at 1.15-4.6 micromol/L (2.5-10 mg/L). Monophasic action potential duration measured at 90% repolarization (MAPD(90)) was not significantly reduced (-1.6 +/- 0.3 msec; P >.05; N.S.) at 1.15 micromol/L, but increased by 6.5 +/- 0.4 msec (P <.05) at 2.3 micromol/L. MAPD(90) was not measurable at 4.6 micromol/L, as a result of inexcitability. Patch-clamp experiments in ventricular myocytes demonstrated a approximately 50% reduction in I(Na) by 10 micromol/L vitamin K and a concentration-dependent reduction of the K(+) current elicited by short depolarizations (250 msec; I(K250)). Estimated IC(50) for I(K250), mostly representing I(Kr), was 2.3 micromol/L. Vitamin K was less potent to block the K(+) current elicited by long depolarizations (5,000 msec; I(K5000)), mostly representing I(Ks), with an estimated IC(50) over 100 micromol/L.

CONCLUSIONS

Therapeutic concentrations ( approximately 1.5 micromol/L) of intravenous vitamin K modulate cardiac action potential by blocking ionic currents involved in cardiac depolarization and repolarization.

Sildenafil (Viagra) prolongs cardiac repolarization by blocking the rapid component of the delayed rectifier potassium current

BACKGROUND-Several cases of unexpected death have been reported with sildenafil in patients predisposed to ischemic cardiac events. Although acute episodes of ischemia could account for some of these deaths, we hypothesized that sildenafil may have unsuspected electrophysiological effects predisposing some patients to proarrhythmia. METHODS AND RESULTS-Studies were undertaken in 10 isolated guinea pig hearts that demonstrated prolongation of cardiac repolarization in a reverse use-dependent manner by sildenafil 30 mcmol/L. Action potential duration increased 15% from baseline 117+/-3 to 134+/-2 ms with sildenafil during pacing at 250 ms cycle length, whereas a 6% increase from 99+/-2 to 105+/-2 ms was seen with pacing at 150 ms cycle length. Experiments in human ether-a-go-go-related gene (HERG)-transfected HEK293 cells (n=30) demonstrated concentration-dependent block of the rapid component (I(Kr)) of the delayed rectifier potassium current: activating current was 50% decreased at 100 mcmol/L. This effect was confirmed using HERG-transfected Chinese hamster ovary (CHO) cells, which exhibit no endogenous I(K)-like current. CONCLUSIONS-Sildenafil possesses direct cardiac electrophysiological effects similar to class III antiarrhythmic drugs. These effects are observed at concentrations that may be found in conditions of impaired drug elimination such as renal or hepatic insufficiency, during coadministration of another CYP3A substrate/inhibitor, or after drug overdose and offer a new potential explanation for sudden death during sildenafil treatment.

Droperidol lengthens cardiac repolarization due to block of the rapid component of the delayed rectifier potassium current

INTRODUCTION

Torsades de pointes have been observed during treatment with droperidol, a butyrophenone neuroleptic agent. Our objectives were (1) to characterize the effects of droperidol on cardiac repolarization and (2) to evaluate effects of droperidol on a major time-dependent outward potassium current involved in cardiac repolarization (I(K)r).

METHODS AND RESULTS

Isolated, buffer-perfused guinea pig hearts (n = 32) were stimulated at different pacing cycle lengths (150 to 250 msec) and exposed to droperidol in concentrations ranging from 10 to 300 nmol/L. Droperidol increased monophasic action potential duration measured at 90% repolarization (MAPD90) in a concentration-dependent manner by 9.8+/-2.3 msec (7.3%+/-0.7%) at 10 nmol/L but by 32.7+/-3.6 msec (25.7%+/-2.2%) at 300 nmol/L (250-msec cycle length). Increase in MAPD90 also was reverse frequency dependent. As noted previously, droperidol 300 nmol/L increased MAPD90 by 32.7+/-3.6 msec (25.7%+/-2.2%) at a pacing cycle length of 250 msec but by only 14.1+/-1.3 msec (13.6%+/-2.3%) at a pacing cycle length of 150 msec. Patch clamp experiments performed in isolated guinea pig ventricular myocytes demonstrated that droperidol decreases the time-dependent outward K+ current elicited by short depolarizations (250 msec; I(K)250) in a concentration-dependent manner. Estimated IC50 for I(K)250, which mostly underlies I(K)r, was 28 nmol/L. Finally, HERG K+ current elicited in HEK293 cells expressing high levels of HERG protein was decreased 50% by droperidol 32.2 nmol/L.

CONCLUSION

Potent block of I(K)r by droperidol is likely to underlie QT prolongation observed in patients treated at therapeutic plasma concentrations (10 to 400 nmol/L) of the drug.

Concomitant Block of the Rapid (I(Kr)) and Slow (I(Ks)) Components of the Delayed Rectifier Potassium Current is Associated With Additional Drug Effects on Lengthening of Cardiac Repolarization

BACKGROUND: The delayed rectifier potassium current, which comprises both a rapid (I(Kr)) and as slow (I(Ks)) component, is a major outward current involved in repolarization of cardiac myocytes. I(Kr) is the target of most drugs that prolong repolarization, whereas electrophysiological effects resulting from combined block of I(Kr) and I(Ks) still need to be characterized. METHODS AND RESULTS: Studies in isolated, buffer-perfused guinea pig hearts were undertaken to compare lengthening of cardiac repolarization under conditions of I(Kr) block alone, I(Ks) Block alone, or combined block of I(Kr) and I(Ks). In protocol A, isolated perfusion with N-acetylprocainamide (NAPA) (I(Kr) block), indapamide (I(Ks) block), or combined NAPA/indapamide was performed at a pacing cycle length of 250 msec. Increases in monophasic action potential duration measured at 90% polarization (MAPD(90)) from baseline after perfusion with NAPA 100 µmol/L (IC(50) for block of I(Kr)) was 19 +/- 6 msed (P <.05), after indapamide 100 µmol/L (EC(50) for block of I(Ks)) 13 +/- 2 msec (P <.05), but 42 +/- 5 msec after combined NAPA 100 µmol/L and indapamide 100 µmol/L (P <.05 vs. baseline and isolated administrations), suggesting the possibility of excessive lengthening of cardiac repolarization by blocking both I(Kr) and I(Ks). As well, in protocol B where sequential perfusions with dofetilide (I(Kr) blocker), dofetilide/indapamide, and indapamide in the same hearts were used, combined dofetilide/indapamide infusion showed a greater increase in MAPD(90) during all pacing cycles studied (250 to 150 msec). CONCLUSIONS: Combined I(Kr) and I(Ks) block may lead to excessive lengthening of cardiac repolarization. This may predispose patients to proarrhythmia during coadministration of drugs.

Thioridazine lengthens repolarization of cardiac ventricular myocytes by blocking the delayed rectifier potassium current

Proarrhythmia has been observed with the antipsychotic agent thioridazine (THIO). The mechanisms underlying these effects are unknown. The objectives of this study were 1) to characterize the effects of THIO on cardiac repolarization and 2) to determine whether lengthening of the Q-T interval could be explained by blocking major K+-repolarizing currents. Isolated, buffer-perfused guinea pig hearts (n = 32) were stimulated at various pacing cycle lengths (150-250 ms) and exposed to THIO at concentrations ranging from 300 nM to 3 microM. THIO increased monophasic action potential duration at 90% repolarization (MAPD90) in a concentration-dependent manner from 14.9 +/- 1.8 at 300 nM to 37.1 +/- 3.2 ms at 3 microM. Increase in MAPD90 was also reverse frequency-dependent; THIO (300 nM) increased MAPD90 by 14.9 +/- 1.8 ms at a pacing cycle length of 250 ms, but by only 7.7 +/- 1.2 ms at a pacing cycle length of 150 ms. Patch-clamp experiments demonstrated that THIO decreases the time-dependent outward K+ current elicited by short depolarizations (250 ms; IK250) in a concentration-dependent manner. Estimated IC50 for IK250, which mostly underlies IKr, was 1.25 microM. Time-dependent outward K+ current elicited in tsA201 cells expressing high levels of HERG protein was also decreased approximately 50% by 1.25 microM THIO. On the other hand, THIO was less potent (IC50 of 14 microM) to decrease time-dependent K+ current elicited by long pulses (5000 ms; IK5000). Under the latter conditions, IK5000 corresponds mainly to IKs. Thus, these results demonstrate block of K+ currents and lengthening of cardiac repolarization by THIO in a concentration-dependent manner. This may provide an explanation of Q-T prolongation observed in some patients treated with THIO.

Block of potassium currents in guinea pig ventricular myocytes and lengthening of cardiac repolarization in man by the histamine H1 receptor antagonist diphenhydramine

Treatment with second generation histamine H1 receptor antagonists has been associated with lengthening of the Q-T interval and proarrhythmia. Similarly, lengthening of the Q-T interval has been reported in patients after overdosing with diphenhydramine (DPH), a first generation agent. Therefore, our study was designed 1) to assess effects of DPH on cardiac repolarization and 2) to characterize effects of the drug on major voltage-dependent cardiac K+ currents. First, we noticed that oral administration of DPH at usual dosages to healthy volunteers or to patients (prior to angioplasty) was associated with prolongation of the Q-Tc interval. Although this effect was modest in most individuals, Q-Tc was increased more than 20 ms in 7 of 20 patients. Second, we noticed that exposure of isolated guinea pig hearts to DPH 10(-5) M caused a lengthening of monophasic action potential duration. This effect was potentiated by the combined perfusion of other K+ channel blockers such as indapamide. Finally, experiments performed with the patch-clamp technique demonstrated unequivocal block of the rapid component of the delayed rectifier (IKr) by DPH; however, IC50 determined for block of IKr (3 x 10(-5) M) is approximately 40-fold greater than plasma concentrations of the drug measured at usual dosages (7 x 10(-7) M). Consequently, in agreement with the long-term clinical use of the drug, prolongation of cardiac repolarization should be minimal in most patients at usual dosages but may be observed with overdosing. Nevertheless, caution remains since excessive lengthening of cardiac repolarization may occur after administration of DPH with other drugs due to 1) concomitant block of other ionic currents or 2) pharmacokinetic interactions leading to toxic concentrations of DPH.

Birthmarks to worry about. Cutaneous markers of dysraphism

Most birthmarks are benign lesions of little concern. On rare occasions, though, congenital cutaneous lesions may indicate an underlying systemic disorder. This article provides an overview of midline cutaneous lesions that are associated with underlying cranial and spina dysraphic conditions.

In vitro characterization of cytochrome P450 2D6 inhibition by classic histamine H1 receptor antagonists

Classic antihistamines, namely diphenhydramine, chlorpheniramine, clemastine, perphenazine, hydroxyzine, and tripelennamine, share structural features with substrates and inhibitors of the polymorphic cytochrome P450 (CYP) isozyme CYP2D6. Therefore, the current study was undertaken to characterize the in vitro inhibition of CYP2D6 by these commonly used, histamine H1 receptor antagonists. Microsomal incubations were performed using bufuralol as a specific CYP2D6 substrate and microsomes derived from human cells transfected with CYP2D6 cDNA. Reaction velocities were assessed in the absence and presence of antihistamines (20 microM) at 11 substrate concentrations (1, 2.5, 5, 7.5, 10, 15, 20, 25, 50, 75, and 100 microM), as well as at three nonsaturating substrate concentrations (2.5, 5, and 20 microM) and three inhibitor concentrations (5, 20, and 50 microM). In the presence of all antihistamines, the Vmax and KM of bufuralol 1'-hydroxylation were significantly altered, compared with the uninhibited reaction (p < 0.05). Lineweaver-Burke plots suggested competitive inhibition of the reaction by diphenhydramine and mixed inhibition by all other antihistamines tested. Diphenhydramine and chlorpheniramine, with estimated Ki values of approximately 11 microM, were the weakest inhibitors of CYP2D6 in vitro. Whereas tripelennamine, promethazine, and hydroxyzine were similar in their inhibitory capacities (Ki approximately 4-6 microM), clemastine appeared to be significantly more potent, with a Ki of approximately 2 microM. These data demonstrate that classic histamine H1 receptor antagonists, available in over-the-counter preparations, inhibit CYP2D6 in vitro. Furthermore, the CYP2D6-inhibitory concentrations of these antihistamines are in the range of their expected hepatic blood concentrations, suggesting that, under specific circumstances, clinically relevant interactions between classic antihistamines and CYP2D6 substrates might occur.

Block of the rapid component of the delayed rectifier potassium current by the prokinetic agent cisapride underlies drug-related lengthening of the QT interval

BACKGROUND

Lengthening of the QT interval and torsades de pointes resulting in cardiac arrests and deaths have been noticed during treatment with cisapride, a newly developed gastrointestinal prokinetic agent. The rapid (I[Kr]) and slow (I[Ks]) components of the delayed rectifier current (I[K]) are candidate ionic currents to explain cisapride-related toxicity because of their role in repolarization of cardiac ventricular myocytes. Our objectives were to (1) characterize effects of cisapride on two major time-dependent outward potassium currents involved in the repolarization of cardiac ventricular myocytes, I(Kr) and I(Ks), and (2) determine action potential-prolonging effects of cisapride on isolated hearts.

METHODS AND RESULTS

A first set of experiments was performed in isolated guinea pig ventricular myocytes with the whole-cell configuration of the patch-clamp technique. Cells were held at -40 mV while time-dependent outward currents were elicited by depolarizing pulses lasting either 250 ms (I[K250]) or 5000 ms (I[K5000]). Effects of cisapride on the I(Kr) component were assessed by measurement of time-dependent activating currents elicited by short pulses (250 ms; I[K250]) to low depolarizing potentials (-20, -10, and 0 mV). Time-dependent activating currents elicited by long pulses (5000 ms; I[K5000]) to positive potentials (>+30 mV) were recorded to assess effects of the drug on the I(Ks) component. A second set of experiments was conducted in isolated guinea pig hearts buffer-perfused in the Langendorff mode to assess effects of the drug on monophasic action potential duration measured at 90% repolarization (MAPD90). Hearts were exposed to cisapride 100 nmol/L at decremental pacing cycle lengths of 250, 225, 200, 175, and 150 ms to determine reverse frequency-dependent effects of the drug. Overall, 112 myocytes were exposed to seven concentrations of cisapride (10 nmol/L to 10 micromol/L). Cisapride inhibited I(Kr), the major time-dependent outward current elicited by short pulses (I[K250]) to low depolarizing potentials, in a concentration-dependent manner with an IC50 of 15 nmol/L (therapeutic levels, 50 to 200 nmol/L). Conversely, block of I(Ks) by the drug was less potent (estimated IC50 >10 micromol/L). In isolated hearts (n=9 experiments), cisapride 100 nmol/L increased MAPD90 by 23+/-3 (P<.05) at a basic cycle length of 250 ms but by only 7+/-1 ms (P<.05) at a basic cycle length of 150 ms.

CONCLUSIONS

Block of I(Kr) gives an explanation to lengthening of cardiac repolarization observed in isolated guinea pig hearts. Potent block of I(Kr) is also likely to underlie prolongation of the QT interval observed in patients receiving clinically recommended doses of cisapride as well as severe cardiac toxicity (torsades de pointes) observed in patients with increased plasma concentrations of the drug.

Block of IKs by the diuretic agent indapamide modulates cardiac electrophysiological effects of the class III antiarrhythmic drug dl-sotalol

Indapamide is a diuretic agent with direct electrophysiological effects on ionic currents involved in cardiac repolarization. In particular, indapamide blocks the slow component of delayed rectifier potassium current. In contrast, most class III antiarrhythmic agents, such as dl-sotalol, block the rapid component of delayed rectifier potassium current. Computer simulations have suggested potentiation of drug effects on cardiac repolarization by the combined block of the rapid component of delayed rectifier potassium current and the slow component of delayed rectifier potassium current. Therefore, the objective of our study was to evaluate the modulation of cardiac electrophysiological effects of dl-sotalol by indapamide. Two indices of cardiac repolarization, monophasic action potential duration at 90% repolarization and effective refractory period, at two basic cycle lengths (800 and 400 msec) were determined in 24 anesthetized open-chest dogs. In two treatment groups (n = 6/group), data were obtained at base line and every 2 min during steadily increasing concentrations of dl-sotalol (0-40 microg/ml) either alone or in the presence of indapamide (500 ng/ml). Data were also obtained in dogs receiving either a low-dose (500 ng/ml) or a high-dose (up to 7.5 microg/ml) infusion regimen of indapamide alone. Administration of dl-sotalol was associated with concentration-dependent increases in monophasic action potential duration at 90% repolarization and effective refractory period, whereas repolarization was only slightly altered by the administration of indapamide alone. However, concentration-response curves of dl-sotalol were shifted to the left in dogs treated with the combination of dl-sotalol and indapamide, and the EC50 values of dl-sotalol estimated for the prolongation of monophasic action potential duration at 90% repolarization and effective refractory period were decreased 3-fold during the coadministration of both drugs (P < .05 vs. dl-sotalol alone). Thus, under conditions of normal K+ levels, clinically relevant concentrations of indapamide modulate dl-sotalol effects on cardiac repolarization. Additional block of cardiac K+ currents, especially the rapid component of delayed rectifier potassium current and the slow component of delayed rectifier potassium current could explain these observations.

Cutaneous granulomas as a presenting sign in ataxia-telangiectasia

Telangiectasia is the classic cutaneous finding of ataxia-telangiectasia (AT) and is often the physical finding that suggests the diagnosis. We report a patient in whom noninfectious cutaneous granulomas were the presenting cutaneous feature of AT and discuss immunodeficiency syndromes that are associated with similar cutaneous granulomas.

'Membranous aplasia cutis' with hair collars. Congenital absence of skin or neuroectodermal defect?

BACKGROUND

The skin and the nervous system are both derived from ectoderm. Separation of neural ectoderm from epithelial ectoderm occurs concurrently with the closure of the neural tube. This chronologic association may explain the cutaneous abnormalities often found overlying neural tube defects. A ring of dark long hair encircling a congenital scalp lesion (the hair collar sign) is one such marker and is often associated with encephaloceles, meningoceles, and heterotopic brain tissue.

OBSERVATIONS

We describe six children with aplasia cutis who displayed the hair collar sign. Aplasia cutis is a relatively heterogeneous disorder; however, these lesions had a unique and strikingly similar appearance. This subtype of aplasia cutis, which we have termed membranous aplasia cutis, shares several clinical and histologic features with cranial neural tube defects.

CONCLUSIONS

We propose that membranous aplasia cutis is a form fruste of a neural tube defect and may be derived from a similar embryological defect. Recent advances in the understanding of cranial neural tube closure may provide support for this hypothesis.

Childhood rosacea

Rosacea usually occurs in adults and rarely has been noted in children. We recently observed three children with rosacea, all of whom responded dramatically to systemic and topical antibiotics. Rosacea in childhood must be distinguished from other erythematous facial disorders, most commonly acne, granulomatous perioral dermatitis, and sarcoidosis. The distribution of facial lesions; the presence of telangiectasias, flushing, and pustules; and the appearance of lesional biopsy sections and the ocular lesions, if present, allow differentiation of rosacea from other facial eruptions.