10 - Miscellaneous drugs

Miscellaneous drugs

© SPMM Course Miscellaneous drugs DRUG MECHANISM Amantadine Used in Parkinsonism. It augments dopaminergic neurotransmission through an unknown mechanism. Dextroamphetamine Methylphenidate

Methylphenidate, dextroamphetamine, and amphetamine are indirectly acting sympathomimetics – induce the release of dopamine and Noradrenaline from presynaptic neurons. Dextroamphetamine and methylphenidate are also weak inhibitors of catecholamine reuptake and inhibitors of monoamine oxidase. Atomoxetine Tricyclic like structure – phenylpropanolamine derivative. Selective inhibitor of the presynaptic noradrenaline reuptake (NARI) similar to the antidepressant reboxetine. Benztropine, Biperiden, Orphenadrine, Procyclidine Anticholinergic drugs. Used in the treatment of EPSEs induced by antipsychotics. Carbidopa Carbidopa inhibits aromatic-L-amino-acid decarboxylase (DOPA Decarboxylase). Administered together with l-dopa as Sinemet to reduce the peripheral conversion of dopa to dopamine. Carbidopa cannot cross the blood-brain barrier. Dantrolene Directly affects the formation of actin-myosin complexes in skeletal muscle through ryanodine calcium channel inhibition. Diphenhydramine, Hydroxyzine, Promethazine, Cyproheptadine. Antihistaminic drugs against central histamine H1 receptor. Cyproheptadine has both a potent antihistamine and serotonin 5-HT2 receptor antagonist properties. All of these agents have some antimuscarinic properties too. Cyproheptadine was used as anti-anorexic agent, and also to treat delayed ejaculation associated with SSRI use. Levodopa Dopamine precursor used in parkinsonism; is combined with carbidopa to reduce peripheral conversion to dopamine. Modafinil Activates hypocretin-producing neurons possibly through alpha 2 and/or alpha-1 adrenergic agonist properties (alerting effects) or some noradrenaline reuptake blocking effects; the stimulating effect of modafinil can be attenuated by prazosin. Pemoline Indirectly stimulates dopaminergic activity - but it has little actual sympathomimetic activity. A stimulant. Withdrawn due to hepatotoxicity. Reserpine

Depletes the stored dopamine and other monoamines from vesicles. Can lead to depression and suicide. Sildenafil Phosphodiesterase-5 Inhibitor. Propranolol .

Beta-adrenergic antagonist. Lipophilic and so can pass blood brain barrier and can have central actions. Reduces akathisia and peripheral signs of sympathetic overdrive seen in anxiety Pramipexole, ropinirole, apomorphine

Apomorphine, pramipexole, and ropinirole are dopamine agonists - bind about 20 times more selectively to dopamine D3 than D2 receptors. Bromocriptine is less selective 2:1. Pergolide is most selective 5:1. Bromocriptine and pergolide are ergotamine derivatives. Pramipexole is a nonergot dopamine agonist. Apomorphine is structurally related to morphine and other opioids. Sumatriptan 5HT1D and 1F agonist Yohimbine It is an alpha 2 antagonist sometimes used in treating erectile dysfunction.

© SPMM Course Lorcaserin, phentermine-topiramate combination, and naltrexone-bupropion combination are novel FDA approved treatment approaches to tackle obesity. These drugs are promoted as anorectic agents, similar to fenfluramine-phentermine combination ('fen-phen'), rimonabant, and sibutramine (all of the latter 3 which fell out of favour due to various adverse effects). Lorcaserin is a serotonin 2C receptor agonist; it is prescribed twice daily with an instruction to discontinue if 5% weight loss is not achieved by 12 weeks. The commonest side effect is a headache. In diabetic patients, this drug can induce hypoglycaemia. Phentermine is a sympathomimetic amine while topiramate is an antiepileptic drug. This combination is used in an extended-release preparation. Side effects include paraesthesia, dysgeusia and dizziness. Naltrexone is an opioid antagonist while bupropion is an aminoketone antidepressant that promotes weight loss in subjects even as a standalone drug (so a prescription of bupropion is not advised in those with a history of eating disorders).