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Apomorphine
Systematic (IUPAC) name
(6aR)- 6-Methyl- 5,6,6a,7-tetrahydro- 4H-dibenzo [de,g] quinoline- 10,11-diol
Identifiers
CAS number 41372-20-7
ATC code G04BE07 N04BC07
PubChem 6005
DrugBank APRD00531
ChemSpider 5783
Chemical data
Formula C 17H17NO2  
Mol. mass 267.322 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Bioavailability 100% following sc injection
Protein binding ~50%
Metabolism hepatic
Half life 40 minutes (range 30-60 minutes)
Excretion  ?
Therapeutic considerations
Pregnancy cat.  ?
Legal status II (California), non-scheduled (Rest of USA)
Routes sc
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Apomorphine (Apokyn, Uprima) is a type of dopaminergic agonist (agonist of the D1 and D2 type dopamine receptors), [1] historically a morphine decomposition product by boiling with concentrated acid, hence the name. It does not actually contain morphine or its skeleton, or bind to opioid receptors. Apomorphine is a relatively non-selective dopamine receptor agonist, having possibly slightly higher affinity for D2-like dopamine receptors.

Historically, apomorphine has been tried for a variety of uses including psychiatric treatment of homosexuality in the early 20th century. Currently, apomorphine is used in the treatment of Parkinson's disease and of erectile dysfunction. It was also successfully used in the treatment of heroin addiction, a purpose for which it was championed by the author William S. Burroughs. It is a potent emetic (i.e. it induces vomiting) and should not be administered without an antiemetic such as domperidone. The emetic properties of apomorphine are exploited in veterinary medicine to induce therapeutic emesis in canines that have recently ingested toxic or foreign substances.

For treatment of erectile dysfunction, it is believed that dopamine receptors in the hypothalamic region of the brain are the main target, as although dopamine receptors in the penis do facilitate erection, they do so far more weakly than those in the brain.[2]

Apomorphine is colourless as a liquid but stains green. Therefore care must be taken to avoid splashes. Apormophine does not remain stable for more than 24 hours in a plastic container, so syringes are discarded if not used within 24 hours.

Contents

Use in Parkinson's disease

First mooted as a treatment for Parkinson's disease as early as 1951,[3] its clinical use was first reported in 1970 by Cotzias et al.,[4] although its emetic properties and short half-life made oral use impractical. A later study found that combining the drug with the antiemetic domperidone improved results significantly.[5]

Therapeutic use in Parkinson's disease is effective because of the drug's strong dopaminergic action, with a rapid effect (within 3–20 minutes of injection) but a brief duration.[6] While apomorphine can be used in combination with l-dopa, the intention is usually to wean patients off of this, as by this stage they will probably be experiencing a great deal of dopa-induced dyskinesias and "off" periods.[6] Following a successful apomorphine challenge, training of patient and caregiver, and careful dose titration, there is no reason why an apomorphine pump cannot be an effective monotherapy.[6]

Erectile dysfunction

Apomorphine hydrochloride (trade name "Uprima") is used in the treatment of erectile dysfunction (male impotence). It is its mode of stimulating dopamine in the brain which is believed to enhance the sexual response. It was found to be of poor efficacy[7] in a large-scale study by Researchers at the UK's Drug Safety Research Unit and University of Portsmouth and discontinued in the UK in January 2006.[7] Around 65-70% of doctors felt it was ineffective, with 60% of over 11,000 patients (avg age 61) discontinuing in month 1 and a further 23% in month 2.[7][8] UK studies concentrated on males with generalized erectile dysfunction. Uprima effects desire and is not meant to produce an overall effect as say Viagra which works on blood flow. In those males who have problems with desire as opposed to generalized erectile dysfunction it works as expected.

Alzheimer's disease

Apomorphine has been reported [9] to be an inhibitor of Beta amyloid fibril formation, and may thus have potential as a therapeutic for Alzheimer's disease

References

  1. ^ Apomorphine-induced activation of dopamine receptors modulates FGF-2 expression in astrocytic cultures and promotes survival of dopaminergic neurons
  2. ^ Matsumoto K, Yoshida M, Andersson K, Hedlund P (2005). "Effects in vitro and in vivo by apomorphine in the rat corpus cavernosum.". Br J Pharmacol 146 (2): 259–67. doi:10.1038/sj.bjp.0706317. PMID 16025145.  
  3. ^ Schwab R, Amador L, Lettvin J. "Apomorphine in Parkinson's disease.". Trans Am Neurol Assoc 56: 251–3. PMID 14913646.  
  4. ^ Cotzias G, Papavasiliou P, Fehling C, Kaufman B, Mena I (1970). "Similarities between neurologic effects of L-dopa and of apomorphine.". N Engl J Med 282 (1): 31–3. PMID 4901383.  
  5. ^ Corsini G, Del Zompo M, Gessa G, Mangoni A (1979). "Therapeutic efficacy of apomorphine combined with an extracerebral inhibitor of dopamine receptors in Parkinson's disease.". Lancet 1 (8123): 954–6. doi:10.1016/S0140-6736(79)91725-2. PMID 87620.  
  6. ^ a b c Chaudhuri K, Clough C (1998). "Subcutaneous apomorphine in Parkinson's disease.". BMJ 316 (7132): 641. PMID 9522772. http://bmj.bmjjournals.com/cgi/content/full/316/7132/641#B2.  
  7. ^ a b c Pharmaceutical Business Review, "Study shows Abbott's Uprima ineffective for most UK patients"
  8. ^ MedicineNet study review
  9. ^ Lashuel HA, Hartley DM, Balakhaneh D, Aggarwal A, Teichberg S, Callaway DJE (2002). "New class of inhibitors of amyloid-beta fibril formation. Implications for the mechanism of pathogenesis in Alzheimer's disease". J Biol Chem 277 (45): 42881–42890. doi:10.1074/jbc.M206593200. PMID 12167652. http://www.jbc.org/cgi/content/abstract/277/45/42881.  

References for 7 and 8 are now broken links.

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