Dopamine Cimetidine

Prolactin-producing hypophyseal adenoma (prolactinoma) is the most common functional pituitary adenoma. Its prevalence peaks in women between 20 and 30 years of age. Hyperprolactinemia can be a cause of infertility and is associated with diminished gonadotropin secretion, secondary amenorrhea, and galactorrhea. The patient should first be examined for drug-induced hyperprolactinemia before any infertility work-up is initiated. For example, antidepressants, cimetidine, dopamine antagonists, reser-pine, sulpiride, verapamil, methyldopa, and estrogen therapy are known to interface with prolactin secretion. 

The phenotiiiazines may decrease the effectiveness of tiie dopamine receptor agonists. When pramipexole is administered concurrently witii cimetidine, ranitidine, verapamil, and quinidine, there is an increased effect of pramipexole When ropinirole is administered with the estrogens, particularly estradiol, there may be an increased effect of ropinirole... 

Uses Obesity Action Blocks uptake of norepinephrine, serotonin, dopamine Dose 10 mg/d PO, may to 5 mg after 4 wk Caution [C, -] w/ SSRIs, Li, dextromethorphan, opioids Contra MAOI w/in 14 d, uncontrolled HTN, arrhythmias Disp Caps SE HA, insomnia, xerostomia, constipation, rhinitis, tach, HTN Interactions T Risk of serotonin synd W/ dextromethorphan, ergots, fentanyl, Li, meperidine, MAOIs, naratriptan, pentazocine, rizatriptan, sumatriptan, SSRIs, tryptophan, zolmitriptan, St. John s wort effects W/ cimetidine, erythromycin, ketoconazole T CNS depression W/ EtOH EMS Use fentanyl w/ caution, may T risk of serotonin synd concurrent EtOH use can T CNS depression OD May cause tach, HTN, diaphoresis, HA, fever, agitation, muscle tremors, and Szs symptomatic and supportive... 

An interesting observation in our structure-activity studies was that ethylamine, a part of the histamine molecule, 4-(2-ethylamine)imidazole, known for a long time to be a potent stimulator of gastric secretion, also produced duodenal ulcers in rats (20,22). Furthermore, structural similarities also exist between dopamine and histamine H receptor antagonists metiamide and cimetidine (23,24). 

Clinically important, potentially hazardous interactions with amprenavir, aprepitant, bedomethasone, buprenorphine, calcium, chloramphenicol, cimetidine, dobazam, clorazepate, cyclosporine, cyproterone, darunavir, dasatinib, delavirdine, dexamethasone, diazoxide, disulfiram, dopamine, fesoterodine, fluconazole, flunisolide, fluoxetine, fosamprenavir, ginkgo biloba, hydrocortisone, imatinib, indinavir, influenza vaccines, isoniazid, isradipine, itraconazole, lacosamide, lapatinib, lopinavir, meperidine, methylprednisolone, midazolam, mivacurium, nelfinavir, nilotinib, nilutamide, phenylbutazone, piracetam, posaconazole, prednisolone, prednisone, primrose, ritonavir, rivaroxaban, sage, saquinavir, solifenacin, St John s wort, sucralfate, telithromycin, temsirolimus, teniposide, ticlopidine, tizanidine, tolvaptan, triamcinolone, uracil/tegafur, vigabatrin... 

Dopamine antagonists (e.g., phenothiazines, haloperidol, methyidopa) Opiates Estrogens H2-antagonists (e.g., cimetidine) MAO inhibitors Dopamine agonists (e.g., levodopa, bromocriptine, pergolide, cabergoline) ... 

Metoclopramide increases gastric transit time, enhancing the absorption of substances absorbed in the small intestine (e.g., ethanol, cyclosporin) and decreasing the absorption of substances absorbed in the stomach (e.g., cimetidine, digoxin). Anticholinergic drugs and dopamine-function-enhancing substances such as levodopa reduce the effectiveness of metoclopramide. Because metoclopramide releases catecholamine, it should be used cautiously with monoamine oxidase inhibitors such as tranylcypromine. Because metoclopramide inhibits plasma cholinesterase, it increases the effectiveness of succinylcholine, a skeletal muscle relaxant. 

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