Meperidine anticholinergic effect

Meperidine Strong agonist with anticholinergic effects... 

Diphenoxylate + Atropine (Lomotil, Lonox) [C-V] [Opioid Antldiarrheal] Uses D Action Constipating meperidine congener, 4-GI motility Dose Adults. Initial, 5 mg PO tid-qid until controlled, then 2.5-5 mg PO bid 20 mg/d max Feds >2 y. 0.3-0.4 mg/kg/24 h (of diphenoxylate) bid-qid, 10 mg/d max Caution [C, +] Contra Obstructive jaundice, D d/t bacterial Infxn children <2 y Disp Tabs, Liq SE Drowsiness, dizziness, xerostomia, blurred vision, urinary retention, constipation Interactions T Effects W/ CNS depressants, opioids, EtOH, T risk HTN crisis W/ MAOIs EMS Monitor for Sxs of electrolyte disturbances and hypovolemia d/t D OD May cause Szs, hypotension, and anticholinergic effects (xerostomia [dry mouth], urine retention, flushed skin) activated charcoal may be effective for OD... 

Meperidine has no spasmolytic effects but an anticholinergic effect, displacing the dose-response curve for carbacholine to the right, indicating competitive antagonism. Only chemically induced spasm of guinea pig large intestine is relaxed by direct application of meperidine solution, possibly due to meperidines local activity. 

Administration of atropine with meperidine (Demerol), flurazepam (Dalmane), diphenhydramine (Benadryl), phenothiazines, and the tricyclic antidepressants may increase the effects of atropine. There is a decreased effectiveness of haloperidol when administered with the anticholinergic dragp. 

Meperidine Demerol) is a phenylpiperidine derivative of morphine that was developed in the late 1930s as a potential antichohnergic agent. It has some anticholinergic side effects that lead to tachycardia, blurred vision, and dry mouth. Meperidine is approximately one-fifth as potent as morphine and is absorbed only half as well when administered oraUy as parenteraUy. It has a rapid onset and short duration of action (2 hours), that is, approximately one-fourth that of morphine. 

Geriatric Considerations - Summary Diphenoxylate is an analog of meperidine and can cause opiate adverse effects. When discontinued, physical dependence and withdrawal symptoms can occur. Adverse GI effects such as constipation, nausea/vomit-ing, and abdominal pain may result from normal doses. Afropine is added to discourage abuse but can cause anticholinergic adverse effects in the older adult. The benefits of f his drug combination for older adulfs are limifed by fhe risk of adverse effects. 

In ordinary doses, meperidine exerts inappreciable effects on respiration and circulation. In large doses, it interferes with the facilitatory function of the pneumotaxic center and the vagal afferent impulses, thereby reducing the rate and depth of respiration. With still higher doses, meperidine produces an irregular respiratory rhythm and ultimately induces apnea. It causes relaxation of the ureter, gall bladder, and bronchi. This action is partly a direct one on the smooth muscle of these structures and, in part, a result of its anticholinergic activity. It does not affect the size of the pupil or alter the tonus of the uterus. 

Additive effects are likely after concomitant use of nortriptyline with CNS depressants, including alcohol, analgesics, barbiturates, narcotics, tranquilizers, and anesthetics (oversedation) atropine and other anticholinergic drugs, including phenothiazines, antihistamines, meperidine, and antiparkinsonian agents (oversedation, paralytic ileus, visual changes, and severe constipation) and metrizamide (increased risk of convulsions). 

Azablcyclane XV was reported to be 6-8 times as potent an analgesic as meperidine but to have much less anticholinergic activity. It was stated that tolerance developed rapidly but no dependence was seen. In a series of 60 analogs (XVI) of profadol, maximum analgesic activity was found with an N-phenethyl group and a free phenolic hydroxyl. Alkylation of the hydroxyl prevented the potentiating effect of the phenethyl substituent. 

The miotic effect of anticholinesterase eye-drops may be potentiated by dexpanthe-nols such as pantothenic acid, a member of the B-vitamin group which forms a part of co-enzyme A, and by clofibrate (Atromid-S). Their effects may be antagonized by longterm corticosteroid therapy, anticholinergics, antihistamines, meperidine, sympatho-mimetics and tricyclic antidepressants. 

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