This code system https://paho.org/fhir/esavi/CodeSystem/WHODrugDC provides a fragment that includes following codes in an undefined heirarchy:

Lvl	Code	Display
1	00000101001	Methyldopa
2	00000101002	Aldomet
2	00000101041	Alfametildopa
2	00000101044	Almedop
2	00000101045	Cardin
2	00000101046	Methyldopum
2	00000101086	Prodop
2	00000101087	Hipermessel
2	00000101089	Tensioval
2	00000101090	Cardiodopa
2	00000101091	Metildopa
2	00000101092	Etildopanan
2	00000101093	Aldotensin
2	00000101094	Angimet
2	00000101095	Metilcord
2	00000101096	Metilprod
2	00000101097	Pressomet
2	00000101098	Metilpress
2	00000101099	Ductomet
2	00000101100	Tildomet
2	00000101101	Kindomet
2	00000101102	Dometil
2	00000101103	Dopametil
2	00000101104	Aldoless
2	00000101105	Aldotil
2	00000101106	Medpress
2	00000101107	Gendomet
2	00000101108	Metilvita
2	00000101109	Dimipress
2	00000101110	Dopatral
2	00000101111	Dopagrand
2	00000101117	Dopasan
2	00000101118	Tensodopa
2	00000101121	Aldopa
2	00000101124	Coradopa
2	00000101135	Tremesal
2	00000101158	Metildopamek
2	00000101173	Toparal
2	00000101178	Hipermet
2	00000101179	Metildopa ethical
2	00000101184	Alpha-methyldopa
2	00000101185	Methyldopum anhydricum
2	00000101187	Metildopa icu-vita
2	00000101188	Venopressin
2	00000101199	Furp metildopa
2	00000101200	Lfm metildopa
2	00000101223	Alfametildopa dutriec
2	00000101224	Dopa pres
2	00000101225	Alfametildopa vivele
2	00000101226	Alfametildopa phi
2	00000101227	Alfametildopa heisecke
2	00000101228	Aditol
2	00000101229	Alfametildopa dallas
2	00000101230	Alfametildopa avanova
2	00000101231	Dopabrit
2	00000101236	Aldoperten
1	00000202001	Orciprenaline sulfate
2	00000202002	Alupent
2	00000202003	Metaprel
2	00000202005	Metaproterenol sulfate
2	00000202011	Metaproterenol
2	00000202022	Metaproternol sulfate
2	00000202023	Orciprenalina
2	00000202030	Orciprenalini sulfas
2	00000202032	Orlin
1	00000301001	Aminosalicylic acid
2	00000301003	Pas
2	00000301007	Para-aminosalicylic acid
2	00000301008	Aminosalylum
2	00000301014	Paser
2	00000301023	4-aminosalicylic acid
1	00000304001	Aminosalicylate sodium
2	00000304004	Sodium pas
2	00000304018	Monopas
2	00000304019	Pas
2	00000304031	Sodium aminosalicylate
2	00000304040	Aminosalicylic acid sodium
2	00000304041	Med pass
1	15268603001	COVID-19 vaccine NRVV Ad (ChAdOx1 nCoV-19)
2	15268603002	AZD 1222
2	15268603003	COVID-19 vaccine AstraZeneca
2	15268603004	Covishield
2	15268603005	ChAdOx1 nCoV-19
2	15268603007	Vaxzevria
2	15268603009	Vacuna COVID-19 AstraZeneca
2	15268603010	Vacina COVID-19 (recombinante)
2	15268603012	COVID-19 vacuna AstraZeneca
1	15268604001	Elasomeran
2	15268604002	Moderna COVID-19 vaccine
2	15268604003	COVID-19 vaccine Moderna
2	15268604004	TAK 919
2	15268604005	MRNA 1273
2	15268604006	CX-024414
2	15268604007	COVID-19 vaccine mRNA (mRNA 1273)
2	15268604008	Spikevax
1	15268607001	COVID-19 vaccine NRVV Ad5 (Ad5-nCoV)
2	15268607002	Ad5-nCoV
2	15268607005	Convidecia
1	15268614001	COVID-19 vaccine inact w.virion NIV-2020-770
2	15268614002	Covaxin
2	15268614003	BBV152
1	15268618001	COVID-19 vaccine prot. subunit (MVC-COV1901)
2	15268618002	Mvc covid-19 vaccine
2	15268618003	MVC-COV1901
1	15268620001	COVID-19 vaccine NRVV Ad5 (Gam-Covid-Vac)
2	15268620002	Gam-COVID-Vac component 2
2	15268620004	Sputnik V component 2
1	15268625001	Tozinameran
2	15268625002	BNT162b2
2	15268625003	Pfizer BioNTech COVID-19 vaccine
2	15268625005	Comirnaty
2	15268625006	COVID-19 vaccine mRNA (BNT162b2)
2	15268625007	Vacuna COVID-19 Pfizer BioNTech
2	15268625008	PF 07305885
2	15268625009	Vacuna Pfizer-BioNTech COVID-19
1	15268628001	COVID-19 vaccine prot. subunit (ZF 2001)
2	15268628003	ZF 2001
2	15268628006	Zifivax
1	15268640001	COVID-19 vaccine NRVV Ad26 (JNJ 78436735)
2	15268640002	JNJ 78436735
2	15268640003	Janssen COVID-19 vaccine
2	15268640004	COVID-19 vaccine Janssen
2	15268640005	Vacuna COVID-19 Janssen
2	15268640006	Vacina COVID-19 (recombinante)
1	15268643001	COVID-19 vaccine inact (Vero) HB02
2	15268643003	BBIBP-CorV
2	15268643005	COVID-19 vaccine (vero cell), inactivated
2	15268643007	Vacuna contra el SARS-COV-2 (Vero Cell), Inactivada
2	15268643009	Hayat vax
2	15268643011	Vacuna SARS-CoV-2 (celulas vero) inactivada
2	15268643012	COVID-19 vaccine inact (Vero) 19nCoV-CDC-Tan-HB02
1	15268644001	COVID-19 vaccine inact (Vero) CZ02
2	15268644002	CoronaVac
2	15268644004	Vacina adsorvida COVID-19 (inativada)
1	15268682001	COVID-19 vaccine prot. subunit (CIGB 66)
2	15268682002	Abdala
2	15268682003	CIGB 66
1	15268684001	COVID-19 vaccine NRVV Ad26 (Gam-Covid-Vac);COVID-19 vaccine NRVV Ad5 (Gam-Covid-Vac)
2	15268684002	Sputnik V
2	15268684003	Gam-COVID-Vac
1	152686A8001	Famtozinameran;Tozinameran
2	152686A8004	Comirnaty bivalente BA.4/BA.5
1	152686AA001	Riltozinameran;Tozinameran
2	152686AA003	Comirnaty bivalente BA.1