Parasympatholytic drugs

Since the therapy with esterase inhibitors is not without risk a poisoning with atropine or other parasympatholytic drugs is treated only symptomatically. 

Pilocarpine is a widely studied peripheral stimulant of the parasympathetic system (101). It is used topically as a myotic to counteract the mydriatic effect of atropine and other parasympatholytic drugs. It has clinical value in the treatment of glaucoma when used as eye drop solutions ranging from 0.5 to 10% in concentration (102). Pilocarpine is reported to stimulate the growth of hair and therefore was employed in hair lotions (1). Internally, it was used as a diaphoretic in the treatment of nephritis (103). 

Several alkaloids derived from histidine occur in plants. Probably the best known of these is pilocarpine (5), found in species of Pilocarpus (Rutaceae) (Fig. 37.2). This compound is a peripheral stimulant of the parasympathetic system and is used topically as a myotic to counteract the mydriatic effects of atropine and other parasympatholytic drugs. Pilocarpine is used for the treatment of glaucoma (as a 0.5-10% solution). 

It is of note that in many parasympatholytic drugs used therapeutically, larger radicals are substituted for the N-methyl group as well as for the acid residue (see Table 8 and Sect B. Chap. S.l). 

The consequences of lack of selectivity can often be avoided if the drug does not require the blood route to reach the target organ, but is, instead, applied locally, as in the administration of parasympatholytics in the form of eye drops or in an aerosol for inhalation. 

Secondary hypotension is a sign of an underlying disease that should be treated first. If stroke volume is too low, as in heart failure, a cardiac glycoside can be given to increase myocardial contractility and stroke volume. When stroke volume is decreased due to insufficient blood volume, plasma substitutes will be helpful in treating blood loss, whereas aldosterone deficiency requires administration of a mineralocor-ticoid (e.g., fludrocortisone). The latter is the drug of choice for orthostatic hypotension due to autonomic failure. A parasympatholytic (or electrical pacemaker) can restore cardiac rate in bradycardia. 

Motion sickness. Effective prophylaxis can be achieved with the parasympatholytic scopolamine (p. 106) and H antihistamines (p. 114) of the diphenyl-methane type (e.g., diphenhydramine, meclizine). Antiemetic activity is not a property shared by all parasympatho-lytics or antihistamines. The efficacy of the drugs mentioned depends on the actual situation of the in vidual (gastric filling, ethanol consumption), environ-... 

All smooth muscle activity which is physiologically under a strong parasympathetic influence is effectively inhibited by atropine, for example in the gastrointestinal, genitourinary and respiratory tract. Parasympatholytics are very useful drugs in the treatment of spastic conditions (colic) in these regions. 

Parasympatholytics are used to induce a mydriasis in the ophthalmology for the examination of the retina. They are applied locally as drops or ointment. The drug-induced inability of the eyes to accommodate results in a serious, although transient, impairment of the visus. Therefore the long-acting atropine (7-10 days) is replaced by short-acting compounds like homatropine (1-3 days), cyclopentolate (1 day) or tropicamide (6 hours). 

Parasympatholytics (Anticholinergic Agents) Section 4 Drugs Acting on Cardiovascular Urinary System 161... 

Anticholinergic Drugs that decrease activity at acetylcholine synapses. These agents are often used to diminish activity in the parasympathetic nervous system (SYN parasympatholytic). 

Homatropine is a synthetic parasympatholytic representing the ester of tropine and mandelic add (Fig. 1). This drug antagonizes acetylcholine on MR and is thus used as mydriatic with less detrimental paralytic effects on ciliary eye muscle than atropine but showing faster and shorter action [1,33], Therefore, it belongs to the WHO list of essential medicines as mydriatic eye drops representing an alternative to atropine [41],... 

From the influence of the autonomic nervous system it follows that all sympatholytic or sympathomimetic and parasympatholytic or parasympathomimetic drugs can produce corresponding effects on cardiac performance. These possibilities are exploited therapeutically for instance, p-blockers for suppressing excessive sympathetic drive (p. 96) ipratropium for treating sinus bradycardia (p. 108). An unwanted activation of the sympathetic system can result from anxiety, pain, and other emotional stress. In these cases, the heart can be protected from harmful stimulation by psychopharmaceuticals such as benzodiazepines (diazepam and others important in myocardial infarction). 

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