Ondansetron

Product NDC: 65084-333
11-digit product format: 650840333
Labeler code: 65084
Product ID: 65084-333_e33c8e05-9243-4c1f-8173-3519b647250c
Type: HUMAN PRESCRIPTION DRUG
Nonproprietary name: Ondansetron
Dosage form: TABLET
Route: ORAL
Labeler: McKesson Corporation dba RX Pak
Application: ANDA077851
Marketing category: ANDA
Marketing start: 2018-07-11
Marketing end: 0000-00-00
Substance: ONDANSETRON HYDROCHLORIDE
Active strength: 8 mg/1
Pharmacologic classes: Serotonin 3 Receptor Antagonists [MoA],Serotonin-3 Receptor Antagonist [EPC]
NDC exclude flag: No
Listing certified through: 2020-12-31
Current FDA listing: Historical FDA.report record

NDC auxiliary status#

These records are reproduced from FDA’s unfinished, excluded, and compounder listings. They describe what appeared in the source files; a missing record does not establish a regulatory status. View all current auxiliary records, including entries without an NDC. · View the auxiliary file history.

Current NDC status page 1 of 1 · 2 matching rows.

Dataset, Scope, Product NDC table
Dataset	Scope	Product NDC	Package NDC	Code	Status	Reporting period	Source date
excluded product	product	65084-333		D	Discontinued by firm		2026-08-17
excluded package	package	65084-333	65084-333-10	D	Discontinued by firm		2026-08-17

Observed NDC auxiliary status history#

This history shows the information present in each captured FDA auxiliary file. It is not a continuous regulatory timeline, and a missing record does not establish a status.

Historic NDC status page 1 of 1 · 24 matching rows.

View current auxiliary records. · View the auxiliary file history.

Captured / source date, Dataset, Scope table
Captured / source date	Dataset	Scope	Package NDC	Snapshot	Source SHA-256
2025-12-14 17:58 UTC · source 2025-12-05	excluded product	product		`d630ba8d3edf…`	`732f749b63fb…`
2025-12-14 17:58 UTC · source 2025-12-05	excluded package	package	65084-333-10	`d630ba8d3edf…`	`732f749b63fb…`
2025-08-27 00:01 UTC · source 2025-08-26	excluded product	product		`f5e01cc5f278…`	`a2eaf40c39c3…`
2025-08-27 00:01 UTC · source 2025-08-26	excluded package	package	65084-333-10	`f5e01cc5f278…`	`a2eaf40c39c3…`
2025-04-01 02:39 UTC · source 2025-03-31	excluded product	product		`2ef7874e63bc…`	`57b86245f4fa…`
2025-04-01 02:39 UTC · source 2025-03-31	excluded package	package	65084-333-10	`2ef7874e63bc…`	`57b86245f4fa…`
2025-03-28 20:22 UTC · source 2025-03-28	excluded product	product		`a1b67e2a42f9…`	`c4cf2c586c0d…`
2025-03-28 20:22 UTC · source 2025-03-28	excluded package	package	65084-333-10	`a1b67e2a42f9…`	`c4cf2c586c0d…`
2025-03-22 03:12 UTC · source 2025-03-21	excluded product	product		`cfe11265f3b6…`	`090c488252e2…`
2025-03-22 03:12 UTC · source 2025-03-21	excluded package	package	65084-333-10	`cfe11265f3b6…`	`090c488252e2…`
2025-03-10 12:48 UTC · source 2025-03-10	excluded product	product		`cdf11ea48f46…`	`ba0047e9e063…`
2025-03-10 12:48 UTC · source 2025-03-10	excluded package	package	65084-333-10	`cdf11ea48f46…`	`ba0047e9e063…`
2025-02-02 03:52 UTC · source 2025-01-31	excluded product	product		`302b2466d912…`	`e7b80fea0513…`
2025-02-02 03:52 UTC · source 2025-01-31	excluded package	package	65084-333-10	`302b2466d912…`	`e7b80fea0513…`
2025-01-20 13:05 UTC · source 2025-01-20	excluded product	product		`ed331223b511…`	`672a5bd82f5f…`
2025-01-20 13:05 UTC · source 2025-01-20	excluded package	package	65084-333-10	`ed331223b511…`	`672a5bd82f5f…`
2025-01-11 03:41 UTC · source 2025-01-10	excluded product	product		`0efc9e666f02…`	`f202fb6c5f17…`
2025-01-11 03:41 UTC · source 2025-01-10	excluded package	package	65084-333-10	`0efc9e666f02…`	`f202fb6c5f17…`
2024-11-09 02:27 UTC · source 2024-11-08	excluded product	product		`ad56d346431e…`	`cc804d4bbf1e…`
2024-11-09 02:27 UTC · source 2024-11-08	excluded package	package	65084-333-10	`ad56d346431e…`	`cc804d4bbf1e…`
2024-10-04 04:10 UTC · source 2024-10-03	excluded product	product		`367a005e9d99…`	`383a685ebd0f…`
2024-10-04 04:10 UTC · source 2024-10-03	excluded package	package	65084-333-10	`367a005e9d99…`	`383a685ebd0f…`
2024-07-10 04:00 UTC · source 2024-07-09	excluded product	product		`557ba5c1ecfa…`	`9c80585c8c6e…`
2024-07-10 04:00 UTC · source 2024-07-09	excluded package	package	65084-333-10	`557ba5c1ecfa…`	`9c80585c8c6e…`

Source provenance: Browse the complete Orange Book source catalog · source snapshot 42.

Orange Book products#

Current product rows page 1 of 1 · 2 matching rows.

Application-product, Trade name, Ingredient table
Application-product	Trade name	Ingredient	Strength	Dosage form / route	TE codes	RLD / RS	Approval date
A077851-001	ONDANSETRON HYDROCHLORIDE	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB		2007-06-25
A077851-002	ONDANSETRON HYDROCHLORIDE	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB		2007-06-25

Therapeutic equivalence codes#

Current TE-code rows page 1 of 1 · 2 matching rows.

Application-product, TE code table
Application-product	TE code
A077851-001	AB
A077851-002	AB

Observed Orange Book product history#

Observed FDA ZIP history: Each table is queried independently by exact application/product key from successfully parsed Orange Book snapshots. Capture times identify archived source observations; absence or a change between snapshots is not inferred. FDA publication files that were not recoverable as structured ZIP data are not represented as states.

Product history page 1 of 3 · 84 observed states.

Captured, Edition, Application-product table
Captured	Edition	Application-product	Trade name	Strength	Dosage form / route	Product TE source text	Approval date	Source SHA-256
2026-08-18 06:07:40	2026-07	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`caaa826d4ba7…`
2026-08-18 06:07:40	2026-07	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`caaa826d4ba7…`
2026-02-19 14:30 UTC	2026-02	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`011fe1cb6892…`
2026-02-19 14:30 UTC	2026-02	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`011fe1cb6892…`
2025-12-14 10:44 UTC · 2 captures of this ZIP	2025-12	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`31067a03dcf5…`
2025-12-14 10:44 UTC · 2 captures of this ZIP	2025-12	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`31067a03dcf5…`
2025-08-23 18:47 UTC	2025-08	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`6a471c1ec25d…`
2025-08-23 18:47 UTC	2025-08	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`6a471c1ec25d…`
2025-03-22 03:13 UTC · 3 captures of this ZIP	2025-03	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`fd3edfee7708…`
2025-03-22 03:13 UTC · 3 captures of this ZIP	2025-03	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`fd3edfee7708…`
2025-02-26 10:13 UTC · 3 captures of this ZIP	2025-02	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`b8a1b40f171c…`
2025-02-26 10:13 UTC · 3 captures of this ZIP	2025-02	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`b8a1b40f171c…`
2025-01-19 17:59 UTC · 7 captures of this ZIP	2025-01	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`03ed91905a0d…`
2025-01-19 17:59 UTC · 7 captures of this ZIP	2025-01	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`03ed91905a0d…`
2024-12-13 21:23 UTC · 2 captures of this ZIP	2024-12	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`2680178bc6a6…`
2024-12-13 21:23 UTC · 2 captures of this ZIP	2024-12	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`2680178bc6a6…`
2024-09-14 05:58 UTC · 2 captures of this ZIP	2024-09	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`5bbf6a4d5a75…`
2024-09-14 05:58 UTC · 2 captures of this ZIP	2024-09	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`5bbf6a4d5a75…`
2024-11-08 22:44 UTC · 3 captures of this ZIP	2024-11	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`d8e5a09893c0…`
2024-11-08 22:44 UTC · 3 captures of this ZIP	2024-11	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`d8e5a09893c0…`
2024-10-29 15:01 UTC	2024-10	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`d06236e962d9…`
2024-10-29 15:01 UTC	2024-10	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`d06236e962d9…`
2024-08-13 05:28 UTC · 3 captures of this ZIP	2024-08	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`79d66fd596c7…`
2024-08-13 05:28 UTC · 3 captures of this ZIP	2024-08	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`79d66fd596c7…`
2024-07-13 05:37 UTC · 2 captures of this ZIP	2024-07	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`301d65b070ca…`
2024-07-13 05:37 UTC · 2 captures of this ZIP	2024-07	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`301d65b070ca…`
2024-06-18 03:08 UTC · 5 captures of this ZIP	2024-06	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`1e350fbaab3a…`
2024-06-18 03:08 UTC · 5 captures of this ZIP	2024-06	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`1e350fbaab3a…`
2024-05-31 18:47 UTC	2024-05	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`8072bd15b7f6…`
2024-05-31 18:47 UTC	2024-05	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`8072bd15b7f6…`
2022-06-29 02:47 UTC · 2 captures of this ZIP	2022-06	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`5c6f7cd8ea54…`
2022-06-29 02:47 UTC · 2 captures of this ZIP	2022-06	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`5c6f7cd8ea54…`
2022-04-08 23:34 UTC	2022-04	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`5d02ea3f76ae…`
2022-04-08 23:34 UTC	2022-04	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`5d02ea3f76ae…`
2022-04-04 05:41 UTC	2022-04	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`4b0b4de00fa7…`
2022-04-04 05:41 UTC	2022-04	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`4b0b4de00fa7…`
2019-12-13 00:20 UTC	2019-12	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`74a2ff9319b5…`
2019-12-13 00:20 UTC	2019-12	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`74a2ff9319b5…`
2022-03-09 01:35 UTC	2022-03	A077851-001	ONDANSETRON HYDROCHLORIDE	EQ 4MG BASE	TABLET / ORAL	AB	2007-06-25	`bb7c543d1eb4…`
2022-03-09 01:35 UTC	2022-03	A077851-002	ONDANSETRON HYDROCHLORIDE	EQ 8MG BASE	TABLET / ORAL	AB	2007-06-25	`bb7c543d1eb4…`

Observed Orange Book normalized TE history#

Normalized TE history page 1 of 3 · 84 observed states.

Captured, Edition, Application-product table
Captured	Edition	Application-product	TE code	Order	Source SHA-256
2026-08-18 06:07:40	2026-07	A077851-001	AB	1	`caaa826d4ba7…`
2026-08-18 06:07:40	2026-07	A077851-002	AB	1	`caaa826d4ba7…`
2026-02-19 14:30 UTC	2026-02	A077851-001	AB	1	`011fe1cb6892…`
2026-02-19 14:30 UTC	2026-02	A077851-002	AB	1	`011fe1cb6892…`
2025-12-14 10:44 UTC · 2 captures of this ZIP	2025-12	A077851-001	AB	1	`31067a03dcf5…`
2025-12-14 10:44 UTC · 2 captures of this ZIP	2025-12	A077851-002	AB	1	`31067a03dcf5…`
2025-08-23 18:47 UTC	2025-08	A077851-001	AB	1	`6a471c1ec25d…`
2025-08-23 18:47 UTC	2025-08	A077851-002	AB	1	`6a471c1ec25d…`
2025-03-22 03:13 UTC · 3 captures of this ZIP	2025-03	A077851-001	AB	1	`fd3edfee7708…`
2025-03-22 03:13 UTC · 3 captures of this ZIP	2025-03	A077851-002	AB	1	`fd3edfee7708…`
2025-02-26 10:13 UTC · 3 captures of this ZIP	2025-02	A077851-001	AB	1	`b8a1b40f171c…`
2025-02-26 10:13 UTC · 3 captures of this ZIP	2025-02	A077851-002	AB	1	`b8a1b40f171c…`
2025-01-19 17:59 UTC · 7 captures of this ZIP	2025-01	A077851-001	AB	1	`03ed91905a0d…`
2025-01-19 17:59 UTC · 7 captures of this ZIP	2025-01	A077851-002	AB	1	`03ed91905a0d…`
2024-12-13 21:23 UTC · 2 captures of this ZIP	2024-12	A077851-001	AB	1	`2680178bc6a6…`
2024-12-13 21:23 UTC · 2 captures of this ZIP	2024-12	A077851-002	AB	1	`2680178bc6a6…`
2024-09-14 05:58 UTC · 2 captures of this ZIP	2024-09	A077851-001	AB	1	`5bbf6a4d5a75…`
2024-09-14 05:58 UTC · 2 captures of this ZIP	2024-09	A077851-002	AB	1	`5bbf6a4d5a75…`
2024-11-08 22:44 UTC · 3 captures of this ZIP	2024-11	A077851-001	AB	1	`d8e5a09893c0…`
2024-11-08 22:44 UTC · 3 captures of this ZIP	2024-11	A077851-002	AB	1	`d8e5a09893c0…`
2024-10-29 15:01 UTC	2024-10	A077851-001	AB	1	`d06236e962d9…`
2024-10-29 15:01 UTC	2024-10	A077851-002	AB	1	`d06236e962d9…`
2024-08-13 05:28 UTC · 3 captures of this ZIP	2024-08	A077851-001	AB	1	`79d66fd596c7…`
2024-08-13 05:28 UTC · 3 captures of this ZIP	2024-08	A077851-002	AB	1	`79d66fd596c7…`
2024-07-13 05:37 UTC · 2 captures of this ZIP	2024-07	A077851-001	AB	1	`301d65b070ca…`
2024-07-13 05:37 UTC · 2 captures of this ZIP	2024-07	A077851-002	AB	1	`301d65b070ca…`
2024-06-18 03:08 UTC · 5 captures of this ZIP	2024-06	A077851-001	AB	1	`1e350fbaab3a…`
2024-06-18 03:08 UTC · 5 captures of this ZIP	2024-06	A077851-002	AB	1	`1e350fbaab3a…`
2024-05-31 18:47 UTC	2024-05	A077851-001	AB	1	`8072bd15b7f6…`
2024-05-31 18:47 UTC	2024-05	A077851-002	AB	1	`8072bd15b7f6…`
2022-06-29 02:47 UTC · 2 captures of this ZIP	2022-06	A077851-001	AB	1	`5c6f7cd8ea54…`
2022-06-29 02:47 UTC · 2 captures of this ZIP	2022-06	A077851-002	AB	1	`5c6f7cd8ea54…`
2022-04-08 23:34 UTC	2022-04	A077851-001	AB	1	`5d02ea3f76ae…`
2022-04-08 23:34 UTC	2022-04	A077851-002	AB	1	`5d02ea3f76ae…`
2022-04-04 05:41 UTC	2022-04	A077851-001	AB	1	`4b0b4de00fa7…`
2022-04-04 05:41 UTC	2022-04	A077851-002	AB	1	`4b0b4de00fa7…`
2019-12-13 00:20 UTC	2019-12	A077851-001	AB	1	`74a2ff9319b5…`
2019-12-13 00:20 UTC	2019-12	A077851-002	AB	1	`74a2ff9319b5…`
2022-03-09 01:35 UTC	2022-03	A077851-001	AB	1	`bb7c543d1eb4…`
2022-03-09 01:35 UTC	2022-03	A077851-002	AB	1	`bb7c543d1eb4…`

FDA-Initiated Inactive NDC Indexing#

NDC, Effective, Action table
NDC	Effective	Action	Document	Indexing SPL	Related label
65084-333-10	2020-07-22	C162847	48780-1	ab0e2407-33d0-f274-e053-dbdaa90a6471	These highlights do not include all the information needed to use ONDANSETRON TABLETS, USP safely and effectively. See full prescribing information for ONDANSETRON TABLETS, USP. ONDANSETRON tablets USP, for oral use Initial U.S. Approval: 1991

openFDA label cross-check#

OpenFDA label data provides additional search and identifier links. DailyMed’s Structured Product Label is the canonical label on FDA.report. Matching records are deduplicated before they are shown below.

Matched openFDA labels page 1 of 1 · 10 matching rows.

Brand, Generic, Manufacturer table
Brand	Generic	Manufacturer	SPL set ID	Effective date	Available safety fields	Join
ondansetron	ONDANSETRON HYDROCHLORIDE	Ascend Laboratories, LLC	2edc0788-dc38-4d21-ba8e-71f159e2d3b1	2026-07-22	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
Ondansetron	ONDANSETRON	REMEDYREPACK INC.	36592150-7e19-474c-9f96-cc8341e28b5d	2026-03-20	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
Ondansetron	ONDANSETRON	Golden State Medical Supply, Inc.	2b9ea1fc-59a4-8189-e063-6394a90a9ae6	2026-01-27	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
Ondansetron	ONDANSETRON	Natco Pharma USA LLC	64527de5-0b92-4340-9243-7a37e8ff96d9	2025-12-19	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
Ondansetron	ONDANSETRON	Bryant Ranch Prepack	f08f56de-8678-4da9-8cae-013a5c393453	2024-10-02	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
Ondansetron	ONDANSETRON TABLETS	Natco Pharma Limited	59c817b7-a1c6-48a5-9bfc-2c381532bfd9	2021-11-29	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
ondansetron	ONDANSETRON HYDROCHLORIDE	Proficient Rx LP	bde7c22c-0047-4735-8df6-b48e8dfa478a	2021-01-01	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
ONDANSETRON	ONDANSETRON	Proficient Rx LP	41c0dc3d-a616-425e-9073-625a0cb692c4	2019-11-01	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
ONDANSETRON	ONDANSETRON	Sun Pharmaceutical Industries, Inc.	834bc56a-657d-4733-9a60-47040cb5c7bf	2019-09-11	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851
ondansetron	ONDANSETRON HYDROCHLORIDE	Bryant Ranch Prepack	37de0550-a6d1-46a8-a0b8-447b0dcf70ad	2019-06-12	Warnings, Adverse reactions	Exact identifier application applno (ANDA): 077851 application number: ANDA077851

UNII, Preferred term, Registry number table
UNII	Preferred term	Registry number	Matched term
NMH84OZK2B	ONDANSETRON HYDROCHLORIDE	103639-04-9	ONDANSETRON HYDROCHLORIDE
4AF302ESOS	ONDANSETRON	99614-02-5	Ondansetron