Homatropine

{{Short description|Medication}}

{{more citations needed|date=October 2021}}

{{Infobox drug

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 461770217

| image = Homatropine.svg

| tradename =

| Drugs.com = {{drugs.com|monograph|homatropine}}

| MedlinePlus = a601006

| pregnancy_category =

| legal_status = Rx only

| routes_of_administration =

| bioavailability =

| protein_bound =

| metabolism =

| elimination_half-life =

| CAS_number_Ref = {{cascite|changed|??}}

| CAS_number = 87-00-3

| ATC_prefix = S01

| ATC_suffix = FA05

| ATC_supplemental =

| PubChem = 6321423

| DrugBank_Ref = {{drugbankcite|changed|drugbank}}

| DrugBank = DB00725

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 16498795

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 8QS6WCL55Z

| ChEMBL_Ref = {{ebicite|changed|EBI}}

| ChEMBL = 1233442

| IUPAC_name = (N-Methyl-8-azabicyclo[3.2.1]oct-3-yl) 2-hydroxy-2-phenylacetate

| C=16 | H=21 | N=1 | O=3

| smiles = CN3[C@H]1CC[C@@H]3C[C@@H](C1)OC(=O)C(O)c2ccccc2

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/C16H21NO3/c1-17-12-7-8-13(17)10-14(9-12)20-16(19)15(18)11-5-3-2-4-6-11/h2-6,12-15,18H,7-10H2,1H3/t12-,13+,14+,15?

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = ZTVIKZXZYLEVOL-MCOXGKPRSA-N

}}

Homatropine (Equipin, Isopto Homatropine) is an anticholinergic medication that is an antagonist at muscarinic acetylcholine receptors and thus the parasympathetic nervous system. It is used in eye drops as a cycloplegic (to temporarily paralyze accommodation), and as a mydriatic (to dilate the pupil).

The related chemical compound homatropine methylbromide (methylhomatropine) is a different medication. Homatropine is less potent than atropine and has a shorter duration of action. It is available as the hydrobromide salt. Homatropine is also given as an atropine substitute,{{cite journal | vauthors = Scharer LL, Burhenne HJ | title = Megacolon associated with administration of an anticholinergic drug in a patient with ulcerative colitis | journal = The American Journal of Digestive Diseases | volume = 9 | issue = 4 | pages = 268–274 | date = April 1964 | pmid = 14142388 | doi = 10.1007/bf02232133 | s2cid = 19169565 }} given to reverse the muscarinic and CNS effects associated with indirect cholinomimetic (anti-AChase) administration.

Homatropine hydrobromide is on the World Health Organization's List of Essential Medicines.{{cite book | vauthors = ((World Health Organization)) | title = The selection and use of essential medicines 2023: web annex A: World Health Organization model list of essential medicines: 23rd list (2023) | year = 2023 | hdl = 10665/371090 | author-link = World Health Organization | publisher = World Health Organization | location = Geneva | id = WHO/MHP/HPS/EML/2023.02 | hdl-access=free }}

It is an antagonist of all five muscarinic acetylcholine receptors.{{cite journal | vauthors = Lavrador M, Cabral AC, Veríssimo MT, Fernandez-Llimos F, Figueiredo IV, Castel-Branco MM | title = A Universal Pharmacological-Based List of Drugs with Anticholinergic Activity | journal = Pharmaceutics | volume = 15 | issue = 1 | date = January 2023 | page = 230 | pmid = 36678858 | pmc = 9863833 | doi = 10.3390/pharmaceutics15010230 | doi-access = free | url = }}