Favipiravir treatment in Thai children with COVID-19: effectiveness, safety, and modeling drug exposure

Demographics and clinical characteristics	COVID-19 non-pneumonia (n = 2,044)			COVID-19 pneumonia (n = 955)
	No FPV (n = 961)	FPV (n = 1,083)	P	No FPV (n = 152)	FPV (n = 803)	P
Age (years)
<5	185 (19.3)	578 (53.4)	<0.001	52 (34.2)	459 (57.2)	<0.001
5–18	776 (80.7)	503 (46.5)		100 (65.8)	344 (42.8)
Biological sex (male)	n = 961	n = 1,081		n = 152	n = 803
	472 (49.1)	588 (54.4)	0.017	79 (52.0)	430 (53.6)	0.211
Underlying conditions	n = 863	n = 981		n = 148	n = 787
	109 (12.6)	290 (29.6)	<0.001	25 (16.9)	186 (23.6)	0.072
Cardiovascular disease	n = 130	n = 335		n = 34	n = 192
	7 (5.4)	30 (9.2)	0.181	1 (2.9)	27 (14.1)	0.070
Gastrointestinal disease	n = 127	n = 320		n = 33	n = 190
	0 (0.0)	1 (0.3)	1.000	0 (0.0)	0 (0.0)	NA
Genetic disease	n = 127	n = 321		n = 34	n = 190
	0 (0.0)	9 (2.8)	0.066	1 (3.0)	8 (4.2)	1.000
Hematologic malignancy	n = 127	n = 321		n = 33	n = 191
	1 (0.8)	16 (5.1)	0.050	1 (3.0)	5 (2.6)	1.000
History of preterm birth	n = 127	n = 320		n = 33	n = 193
	0 (0.0)	11 (3.4)	0.039	0 (0.0)	15 (7.8)	0.136
Neurological disease	n = 128	n = 323		n = 34	n = 192
	4 (3.1)	11 (3.4)	1.000	2 (5.9)	17 (8.9)	0.746
Pulmonary disease	n = 139	n = 331		n = 35	n = 201
	44 (31.7)	80 (24.2)	0.093	6 (17.1)	56 (27.9)	0.184
Obesity	n = 128	n = 327		n = 33	n = 193	0.214
	9 (7.0)	33 (10.1)	0.311	1 (3.0)	21 (10.9)
Renal disease	n = 127	n = 321		n = 33	n = 190
	0 (0.0)	3 (0.9)	0.562	0 (0.0)	2 (1.1)	1.000
Rheumatological disease	n = 127	n = 320		n = 33	n = 190
	0 (0.0)	3 (0.9)	0.562	0 (0.0)	1 (0.5)	1.000
Solid tumor	n = 127	n = 321		n = 33	n = 191
	0 (0.0)	4 (1.3)	0.581	0 (0.0)	6 (3.1)	0.596
Transplantation	n = 127	n = 320		n = 33	n = 191
	0 (0.0)	3 (0.9)	0.562	0 (0.0)	2 (1.1)	1.000
COVID-19 vaccination	n = 555	n = 619		n = 134	n = 617
	14 (2.5)	28 (4.5)	0.065	1 (0.8)	10 (1.6)	0.699
Predominant strain during infection^†	n = 961	n = 1,083		n = 152	n = 803
Pre-delta/omicron	314 (32.7)	62 (5.7)	<0.001	71 (46.7)	134 (16.7)	<0.001
Delta	477 (49.6)	319 (29.5)		65 (42.8)	317 (39.5)
Omicron	170 (17.7)	702 (64.8)		16 (10.5)	352 (43.8)
SARS-CoV-2 Diagnosis
Rapid antigen test	144 (98.0)	277 (95.2)	0.196	12 (92.3)	146 (96.1)	0.443
	n = 147	n = 291		n = 13	n = 152
Waves
Pre-delta/omicron	1 (100)	1 (100)	NA	2 (100)	2 (100)	NA
Delta	52 (98.1)	40 (95.2)	0.582	3 (100)	32 (100)	NA
Omicron	91 (97.9)	236 (95.2)	0.366	7 (88.0)	112 (94.9)	0.376
Sites
Non-hospital	101 (99.0)	49 (98.0)	0.551	3 (100)	14 (100)	NA
Hospital	43 (95.6)	228 (94.6)	1.000	9 (90.0)	132 (95.7)	0.394
RT-PCR	841 (99.8)	973 (99.6)	0.692	149 (100)	760 (100)	NA
	n = 843	n = 977		n = 149	n = 760
Waves
Pre-delta/omicron	298 (99.3)	58 (100)	1.000	70 (100)	130 (100)	NA
Delta	447 (100)	306 (100)	NA	64 (100)	304 (100)	NA
Omicron	96 (100)	609 (99.4)	1.000	15 (100)	326 (100)	NA
Sites
Non-hospital	477 (99.6)	106 (100)	1.000	68 (100)	151 (100)	NA
Hospital	364 (100)	867 (99.5)	0.326	81 (100)	609 (100)	NA
Ct of SARS-CoV-2 RT-PCR at diagnosis, mean ± SD
N gene	n = 628	n = 773		n = 124	n = 629
	24.2 ± 6.2	20.8 ± 5.8	<0.001	24.3 ± 5.6	22.4 ± 6.1	0.001
ORF gene	n = 399	n = 607		n = 100	n = 531
	25.2 ± 6.9	22.0 ± 5.9	<0.001	24.0 ± 5.6	22.3 ± 5.9	0.008
Clinical severity	n = 961	n = 1,083		n = 152	n = 803
Mild	961 (100.0)	1,083 (100.0)	NA	-	-	0.007
Moderate	-	-		147 (96.7)	708 (88.2)
Severe	-	-		4 (2.6)	82 (10.2)
Critical illness	-	-		1 (0.7)	13 (1.6)
Outcomes of treatment
Duration (days) of FPV treatment, median (IQR)		n = 1,071			n = 801
	-	4 (4–5)	NA	-	4 (4–5)	NA
Duration (days) between diagnosis and FPV initiation, median (IQR)		n = 1,077			n = 802
	-	1 (0–1)	NA	-	1 (0–2)	NA
Duration (days) between symptom onset to FPV initiation, median (IQR)		n = 1,046			n = 673
	-	1 (1–3)	NA	-	2 (1–3)	NA
Received antibiotics	5 (0.5)	44 (4.1)	<0.001	7 (4.6)	89 (11.1)	0.015
Received corticosteroids	3 (0.3)	25 (2.3)	<0.001	2 (1.3)	69 (8.6)	0.002
Received oxygenation	0 (0.0)	8 (0.7)	0.008	0 (0.0)	98 (12.2)	<0.001
Isolation
Home/community	296 (30.8)	77 (7.1)	<0.001	21 (13.8)	74 (9.2)	<0.001
Field hospital	263 (27.4)	61 (5.6)		49 (32.3)	83 (10.3)
Hospital	402 (41.8)	945 (87.3)		82 (54.0)	646 (80.5)
Duration of fever (days), median (IQR)	n = 55 8 (5–14)	n = 590 6 (5–8)	0.012	n = 23 14 (10–14)	n = 382 7 (5–9)	<0.001
Condition at discharge	n = 946	n = 1,025
Complete recovery	889 (94.0)	997 (97.3)	<0.001	144 (94.7)	691 (87.8)	0.013
Partial recovery	57 (6.0)	28 (2.7)		7 (4.6)	96 (12.2)
Death	0 (0.0)	0 (0.0)		1 (0.7)	0 (0.0)
Length of hospital admission, median (IQR)	n = 663 10 (7–11)	n = 1,002 5 (3–8)	<0.001	n = 130 11 (8–13)	n = 720 8 (5–11)	<0.001
Hospital	9 (6–10) n = 401	5 (3–8) n = 941	<0.001	12 (8–13) n = 81	8 (4–10) n = 638	<0.001
Field hospital	10 (8–12) n = 262	11 (9–12) n = 61	0.074	10 (8–12) n = 49	11 (9–13) n = 82	0.074

1 Mann-Whitney U or Student’s t-tests were used to compare continuous variables. Data are presented as n (%) unless stated otherwise.

1† The ancestral Wuhan strain and alpha variant were the predominant circulating strains during the first to third waves (Pre-delta/omicron). Delta and omicron variants were the predominant circulating strains during the fourth and fifth waves, respectively.

1 COVID-19, coronavirus disease 2019; Ct, cycle threshold; FPV, favipiravir; IQR, interquartile range; NA, not applicable; N gene, nucleocapsid gene; ORF gene, open reading frame gene; RT-PCR, reverse transcription polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SD, standard deviation.

Table 2.

Potential factors for predicting clinical recovery at discharge of patients with and without COVID-19 pneumonia

Factors	COVID-19 non-pneumonia				COVID-19 pneumonia
	OR (95% CI)	P	aOR (95% CI)	P	OR (95% CI)	P	aOR (95% CI)	P
Age (years)
<5	2.4 (1.4, 4.1)	0.002	1.9 (1.1, 3.3)	0.030
5–18	Reference		Reference
Underlying disease
History of preterm birth					0.3 (0.1, 0.9)	0.033	0.2 (0.1, 0.7)	0.011
Pulmonary disease					0.4 (0.2, 0.9)	0.031	0.4 (0.2, 0.9)	0.028
Predominant strain during infection†
Pre-delta/omicron	Reference				Reference
Delta	1.3 (0.8, 2.1)	0.360			0.2 (0.1, 0.5)	<0.001
Omicron	3.2 (1.7, 5.9)	<0.001			0.3 (0.1, 0.7)	0.003
Treatment
FPV	2.3 (1.4, 3.6)	<0.001	1.9 (1.2, 3.1)	0.010	0.4 (0.2, 0.8)	0.016
ICU admission					0.2 (0.1, 0.5)	<0.001	0.1 (0.1, 0.4)	0.001

1 Factors with P < 0.10 in the univariable analysis were included in multivariable analyses.

1 aOR, adjusted odds ratio; CI, confidence interval; COVID-19, coronavirus disease 2019; FPV, favipiravir; ICU, intensive care unit; OR, odds ratio.

Table 3.

Factors associated with fever duration in COVID-19 participants who had a fever at baseline (n = 2,076 participants)

Variables	Coefficient(d)	(95% CI)	P	Coefficient(d)	(95% CI)	P
Age (years)
<5	Reference
≥5	1.1	(0.74, 1.55)	<0.001
Biological sex
Male	Reference
Female	0.08	(–0.33, 0.49)	0.704
Underlying disease	–0.03	(–0.50, 0.43)	0.890
History of COVID-19 vaccination	–1.12	(–2.39, 0.14)	0.082
Predominant strain during infection^†
Pre-delta/pre-omicron	Reference
Delta	–0.38	(–1.21,0.46)	0.377
Omicron	–3.33	(–4.12, –2.55)	<0.001	–3.02	(–3.85, –2.19)	<0.001
Clinical severity
Non-pneumonia	Reference
Pneumonia	0.73	(0.32, 1.15)	0.001	0.49	(0.07, 0.90)	0.022
Treatment
FPV	–3.21	(–3.99, –2.44)	<0.001	–2.66	(–3.44, –1.88)	<0.001
Antibiotics	1.1	(0.30, 1.92)	0.008
Time from COVID-19 diagnosis until FPV	0.94	(0.80, 1.08)	<0.001
administration (d)

1 Factors with P < 0.10 in the univariable analysis were included in multivariable analyses.

1 CI, confidence interval; COVID-19, coronavirus disease 2019; FPV, favipiravir; RT-PCR, reverse transcription polymerase chain reaction.

Simulations of FPV plasma PK in Thai children and adolescents weighing 3 kg, 5 kg, 8 kg, 10 kg, 20 kg, and 35 kg. PK parameter values at these weights were derived from allometric scaling of plasma PK observed in Thai adults weighing 60 kg. BID, twice daily; CL, clearance; Ctrough, trough concentration; D, day; EC90, 90% effective concentration; FPV, favipiravir; IP, investigational product; KA, absorption rate constant; PK, pharmacokinetics; Vd, volume of distribution.

Supplementary Table 1.

Clinical manifestations of COVID-19 patients with and without pneumonia and favipiravir treatment at the time of diagnosis

Clinical manifestations	COVID-19 non-pneumonia			COVID-19 pneumonia
	No FPV n = 961	FPV n = 1083	P	No FPV n = 152	FPV n = 803	P
Fever	497 (52.0) n = 956	912 (84.5) n = 1079	<0.001	53 (34.9) n = 152	614 (76.7) n = 801	<0.001
Chills	4 (0.4) n = 956	8 (0.7) n = 1079	0.397	1 (0.7) n = 152	2 (0.3) n = 801	0.804
Conjunctivitis	3 (2.1) n = 140	2 (1.4) n = 147	0.678	0 (0.0) n = 20	2 (0.9) n = 233	1.000
Nasal discharge	450 (48.7) n = 925	446 (41.9) n = 1065	0.002	69 (59.0) n = 117	357 (46.7) n = 765	0.013
Dyspnea	13 (1.4) n = 919	20 (1.9) n = 1060	0.413	5 (4.4) n = 115	76 (10.0) n = 763	0.053
Cough	654 (70.3) n = 930	661 (61.9) n = 1068	<0.001	90 (77.6) n = 116	542 (70.6) n = 768	0.119
Abdominal pain	11 (1.2) n = 920	21 (2.0) n = 1060	0.167	5 (4.4) n = 115	5 (0.7) n =763	0.005
Diarrhea	78 (8.5) n = 921	142 (13.4) n = 1062	<0.001	13 (11.3) n = 115	102 (13.3) n = 765	0.547
Nausea/vomiting	38 (4.1) n = 920	207 (19.5) n = 1062	<0.001	9 (7.8) n = 115	120 (15.7) n = 763	0.026
Rash	5 (0.5) n = 919	7 (0.7) n = 1060	0.740	0 (0) n = 115	3 (0.4) n = 763	1.000
Febrile seizure	0 (0.0) n = 919	18 (1.7) n = 1060	<0.001	2 (1.7) n = 115	38 (5.0) n = 763	0.120

1 Mann–Whitney U or Student’s t-tests were used to compare continuous variables. Data are presented as n (%) unless stated otherwise.

1 COVID-19, coronavirus disease 2019; FPV, favipiravir.

Supplementary Table 2.

Demographic and clinical characteristics of COVID-19 participants with and without pneumonia and partial or complete clinical recovery at discharge.

Potential factors	COVID-19 non-pneumonia			COVID-19 pneumonia
	Partial clinical recovery (n = 85)	Complete clinical recovery (n = 1886)	P	Partial clinical recovery (n = 104	Complete clinical recovery (n = 835)	P
Age (years)
<5	17 (20.0)	700 (37.1)	0.001	57 (54.8)	443 (52.7)	0.735
5–18	68 (80.0)	1,184 (62.8)		47 (45.2)	392 (47.0)
Biological sex (male)	37 (43.5) n = 85	983 (52.2) n = 1884	0.119	54 (51.9)	439 (52.6)	0.900
Underlying disease or condition	14 (16.7) n = 84	367 (21.6) n = 1696	0.278	33 (32.4) n = 102	174 (21.3) n = 819	0.011
Cardiovascular disease	1 (6.7) n = 15	35 (8.4) n = 417	1.000	5 (16.1) n = 31	22 (11.5) n = 191	0.466
Gastrointestinal disease	0 (0.0)	0 (0.0)	NA	2 (2.0) n = 98	0 (0.0) n = 804	0.012
Genetic disease	0 (0.0) n = 15	6 (1.4) n = 411	1.000	1 (3.2) n = 31	8 (4.2) n = 189	1.000
Hematologic malignancy	0 (0.0) n = 15	17 (4.1) n = 411	1.000	0 (0.0) n = 31	6 (3.2) n = 189	0.598
History of preterm birth	1 (6.7) n = 15	10 (2.4) n = 410	0.330	5 (16.1) n = 31	10 (5.2) n = 191	0.025
Neurological disease	0 (0.0) n = 15	12 (2.9) n = 414	1.000	5 (14.7) n = 34	13 (6.9) n = 188	0.164
Obesity	2 (13.3) n = 15	39 (9.4) n = 417	0.644	3 (9.7) n = 31	19 (10.0) n = 191	1.000
Pulmonary disease	6 (40.0) n = 15	117 (27.0) n = 433	0.255	14 (42.4) n = 33	48 (24.1) n = 199	0.028
Renal disease	0 (0.0) n = 15	3 (0.7) n = 411	1.000	0 (0.0) n = 31	2 (1.1) n = 188	1.000
Rheumatological disease	0 (0.0) n = 15	3 (0.7) n = 410	1.000	0 (0.0) n = 31	1 (0.5) n = 188	1.000
Solid tumor	0 (0.0) n = 15	4 (1.0) n = 411	1.000	1 (3.2) n = 31	5 (2.7) n = 189	1.000
Transplantation	0 (0.0) n = 15	3 (0.7) n = 410	1.000	0 (0.0) n = 31	2 (1.1) n = 189	1.000
COVID-19 vaccination	4 (8.3) n = 48	36 (3.3) n = 36	0.080	1 (1.4) n = 71	7(1.2) n = 596	0.596
Predominant strain during infection^†			<0.001			<0.001
Pre-delta/pre-omicron	25 (29.4)	347 (18.4)		8 (7.7)	195 (23.4)
Delta	42 (49.4)	740 (39.2)		55 (52.9)	327 (39.2)
Omicron	18 (21.2)	799 (42.4)		41 (39.4)	313 (37.5)
Ct of SARS-CoV-2 RT-PCR, median (IQR)
N gene	20.2 (17–24) n = 60	21.3 (17.6–26.5) n = 1306	0.078	21.5 (18.3–25.2) n = 87	21.4 (18.3–26.8) n = 656	0.769
ORF gene	22.2 (16.7–25) n = 30	22 (18.4–27.9) n = 945	0.400	20.8 (17.5–25) n = 68	21.1 (18.5–25.9) n = 550	0.458
Clinical severity						0.001
Mild	85 (100)	1,883 (100)	NA	-	-
Moderate	-	-		89 (85.6)	751 (89.9)
Severe	-	-		9 (8.7)	76 (9.1)
Critical	-	-		6 (5.8)	8 (1.0)
Laboratory results at COVID-19 diagnosis
Anemia	11 (73.3) n = 15	253 (69.1) n = 366	1.000	12 (63.2) n = 19	99 (64.7) n = 153	0.894
Leukopenia	1 (6.7) n = 15	59 (16.2) n = 366	0.483	3 (15.8) n = 19	29 (18.8) n = 154	1.000
Neutropenia	1 (6.7) n = 15	37 (15.2) n = 243	0.705	3 (15.8) n = 19	20 (13.0) n = 154	0.722
Lymphopenia	2 (13.3) n = 15	64 (26.5) n = 242	0.367	3 (15.8) n = 19	46 (28.9) n = 154	0.282
Thrombocytopenia	0 (0.0) n = 15	8 (2.1) n = 371	1.000	3 (15.8) n = 19	2 (1.3) n = 151	0.010
Elevated AST	1 (16.7) n = 6	46 (18.7) n = 246	1.000	2 (28.6) n = 7	13 (25.5) n = 51	1.000
Elevated ALT	0 (0.0) n = 6	22 (8.9) n = 246	1.000	2 (28.6) n = 7	9 (18.0) n = 50	0.610
Elevated TB	0 (0.0) n = 4	3 (1.7) n = 172	1.000	1 (25.0) n = 4	0 (0.0) n = 42	0.087
Elevated DB	0 (0.0) n = 4	7 (4.1) n = 172	1.000	2 (50.0) n = 4	0 (0.0) n = 42	0.006
Hypoalbuminemia	0 (0.0) n = 4	2 (1.2) n = 172	1.000	1 (25.0) n = 4	3 (7.3) n = 41	0.320
CRP (mg/L), median (IQR)	3.4 (2.9–7.7) n = 5	1.6 (0.6–4.2) n = 117	0.080	5.2 (3.8–9.5) n = 7	3.0 (1.8–13.0) n = 36	0.377
Treatment
FPV	28 (32.9)	997 (52.9)	<0.001	96 (92.3)	691 (82.8)	0.013
Steroids	0 (0.0)	27 (1.4)	0.628	8 (7.7)	63 (7.5)	0.957
Antibiotics	2 (2.4)	47 (2.5)	1.000	15 (14.4)	80 (9.6)	0.123
Antifungal agents	0 (0.0)	1 (0.1)	1.000	0 (0.0)	0 (0.0)	NA
Oxygenation	0 (0.0)	7 (0.4)	1.000	14 (13.5)	84 (10.1)	0.285
ICU admission	0 (0.0)	4 (0.2)	1.000	14 (13.5)	35 (4.2)	<0.001
Duration of ICU stay, median (IQR)	0 (0.0)	5 (3–8) n = 3	NA	3 (2.5–8) n = 8	7.5 (4.5–11) n = 28	0.073
Duration of FPV administration, median (IQR)	4 (4–5) n = 28		0.893	4 (4–5) n = 96	4 (4–5) n = 689	0.069
Time from diagnosis until FPV administration, median (IQR)	1 (1–2) n = 28	1 (0–1) n = 993	0.075	1 (0–2) n = 96	1 (0–2) n = 690	0.834
Time from COVID-19 symptom onset until FPV administration, median (IQR)	2 (1–3) n = 27	1 (1–3) n = 967	0.407	1 (1–3) n = 69	2 (1–3.5) n = 588	0.354

1 Mann–Whitney U or Student’s t-tests were used to compare continuous variables. Data presented as n (%) unless stated otherwise.

1† The ancestral Wuhan strain and alpha variant were the predominant circulating strains during the first to third waves (Pre-delta/omicron); delta and omicron variants were the predominant circulating strains during the fourth and fifth waves, respectively.

1 ALT, alanine transaminase; AST, aspartate transaminase; COVID-19, coronavirus disease 2019; Ct, cycle threshold; CRP, C-reactive protein;

1 DB, direct bilirubin; FPV, favipiravir; ICU, intensive care unit; IQR, interquartile range; NA, not applicable; N gene, nucleocapsid gene; ORF gene, open reading frame gene; RT-PCR, reverse transcription polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SD, standard deviation; TB, total bilirubin.

Supplementary Table 3.

Laboratory results at FPV treatment initiation and completion for patients with and without COVID-19 pneumonia

	COVID-19 non-pneumonia			COVID-19 pneumonia
	Treatment initiation	Treatment completion	P	Treatment initiation	Treatment completion	P
Hematocrit, median (IQR)	36.5 (33.9–38.5) n = 120	36.6 (34.1–39) n = 750	0.569	36.7 (34.8–39.1) n = 537	0.493
Anemia	90 (75) n = 120	519 (69.3) n = 749	0.205	58 (60.4) n = 96	341 (63.5) n = 537	0.564
WBC (cells/mm³), median (IQR)	7,295 (5,210–9,345) n = 120	6,970 (5,380–9,260) n = 751	0.947	7,750 (6,145–9,775) n = 96	7,810 (5,900–9,950) n = 535	0.961
Leukopenia	24 (20) n = 120	151 (20) n = 750	0.973	17 (17.7) n = 96	86 (16.1) n = 535	0.690
ALC (cells/mm³), median (IQR)	1,539 (776–4;3,120) n = 93	2,444 (1,346–4,329) n = 666	<0.001	2,295 (1,475–4,556) n = 96	2,806 (1,616–4,681) n = 464	0.186
Lymphopenia	51 (54.8) n = 93	288 (43.3) n = 665	0.036	37 (38.5) n = 96	200 (37.5) n = 533	0.850
ANC (cells/mm³), median (IQR)	4,277 (2,280–6,497) n = 94	3,172 (1,946–5,096) n = 668	0.005	3,520 (2,110–5,661) n = 96	3,197 (1,981–5,200) n = 533	0.272
Neutropenia	8 (8.5) n = 94	106 (15.9) n = 667	0.060	11 (11.5) n = 96	85 (16) n = 533	0.260
Platelet × 103 (cells/mm³), median (IQR)	284 (223–326) n = 120	278 (226–337) n = 753	0.862	269 (236–333) n = 93	289 (230–356) n = 535	0.649
Thrombocytopenia	4 (3.3) n = 120	26 (3.5) n = 753	1.000	2 (2.2) n = 93	27 (5.1) n = 535	0.290
AST (U/L), median (IQR)	30 (22–37) n = 77	37 (27–47) n = 652	0.001	44 (27–49) n = 34	39 (30–50) n = 331	0.808
Elevated AST	12 (15.6) n = 77	191 (29.3) n = 651	0.011	8 (23.5) n = 34	115 (34.7) n = 331	0.188
ALT (U/L), median (IQR)	16 (12–21) n = 26	18 (13–25) n = 652	0.023	19 (16–25) n = 33	20 (14–29) n = 330	0.829
Elevated ALT	6 (7.8) n = 77	59 (9.1) n = 651	0.712	4 (12.1) n = 33	50 (15.2) n = 330	0.800
TB (mg/dL), median (IQR)	0.3 (0.2–0.4) n = 34	0.3 (0.2–0.4) n = 219	0.661	0.3 (0.2–0.4) n = 24	0.3 (0.2–0.5) n = 174	0.099
Elevated TB	2 (5.9) n = 34	5 (2.3) n = 219	0.239	1 (4.2) n = 24	3 (1.7) n = 174	0.406
DB (mg/dL), median (IQR)	0.1 (0.1–0.2) n = 32	0.1 (0.1–0.2) n = 211	0.735	0.1 (0.1–0.2) n = 23	0.1 (0.1–0.2) n = 170	0.107
Elevated DB	2 (5.9) n = 34	11 (5.0) n = 219	0.689	1 (4.2) n = 24	11 (6.3)n = 174	1.000
Albumin (g/L), median (IQR)	45 (42–47) n = 37	44 (41–47) n = 232	0.481	44 (42–46) n = 24	43 (40–46)–n = 188	0.105
Hypoalbuminemia	1 (2.7) n = 37	13 (5.6) n = 232	0.700	0 (0) n = 24	13 (6.9) n = 188	0.370

1 Mann–Whitney U or Student’s t-tests were used to compare continuous variables. Data presented as n (%) unless stated otherwise. Anemia, lymphopenia and thrombocytopenia, elevated AST, ALT, alkaline phosphatase, and albumin were determined according to age reference values [1].

1 ALC, absolute lymphocyte count; ALT, alanine transaminase; ANC, absolute neutrophil count; AST, aspartate transaminase; COVID-19, coronavirus disease 2019; DB, direct bilirubin; FPV, favipiravir; IQR, interquartile range; NA, not applicable; TB, total bilirubin; WBC, white blood cell.

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DOI: https://doi.org/10.2478/abm-2026-0011 | Journal eISSN: 1875-855X | Journal ISSN: 1905-7415

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Language: English

Page range: 96 - 113

Published on: Apr 30, 2026

Published by: Chulalongkorn University

In partnership with: Paradigm Publishing Services

Keywords:

children,

COVID-19,

favipiravir,

pharmacokinetic modeling,

Thailand

Related subjects:

Medicine,

Assistive professions, nursing,

Basic medical science,

Basic medical science, other,

Clinical medicine,

Clinical medicine, other

© 2026 Sujittra Chaisavaneeyakorn, Nopporn Apiwattanakul, Chonnamet Techasaensiri, Nattakarn Tantawarak, Bandit Thinkhamrop, Supattra Rungmaitree, Siriporn Phongjitsiri, Tavitiya Sudjaritruk, Suvaporn Anugulruengkitt, Pope Kosalaraksa, Thirapa Nivesvivat, Puttichart Khantee, Pornumpa Bunjoungmanee, Panit Takkinsatian, Thiraporn Kanjanaphan, Rudiwilai Samakoses, Tim R. Cressey, Henry Pertinez, Andrew Owen, Kulkanya Chokephaibulkit, published by Chulalongkorn University
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 20 (2026): Issue 2 (April 2026)

Favipiravir treatment in Thai children with COVID-19: effectiveness, safety, and modeling drug exposure

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