Meperidine parenteral administration

The answer is c. (Hardman, pp 543—544. Katzang, p 2533) Fentanyl is a chemical relative of meperidine that is nearly 100 times more potent than morphine. The duration of action, usually between 30 and 60 min after parenteral administration, is shorter than that of meperidine. Fentanyl citrate is only available for parenteral administration intramuscularly and intravenously. Tran sbuc cal ( lollipop ) and transdermal patches avoid first-pass metabolism of fentanyl. 

Spasmolytics. N-Butylscopolamine (p. 104) is used for the relief of painful spasms of the biliary or ureteral ducts. Its poor absorption (N.B. quaternary N absorption rate <10%) necessitates parenteral administration. Because the therapeutic effect is usually weak, a potent analgesic is given concurrently, e.g., the opioid meperidine. Note that some spasms of intestinal musculature can be effectively relieved by organic nitrates (in biliary colic) or by nifedipine (esophageal hypertension and achalasia). 

The IV or IM administration of parenteral narcotics (meperidine, morphine, fentanyl) is commonly used to treat the pain associated with labor. Compared to epidural analgesia, parenteral opioids are associated with lower rates of oxytocin augmentation, shorter stages of labor, and fewer instrumental deliveries. 

Relief of pain - While subcutaneous administration is suitable for occasional use, IM administration is preferred for repeated doses. If IV administration is required, decrease dosage and inject very slowly, preferably using a diluted solution. Meperidine is less effective when administered orally than when given parenterally. Reduce proportionately (usually by 25% to 50%) when administering concomitantly with phenothiazines and other tranquilizers. 

Diphenoxylate is a synthetic meperidine analog with little or no analgesic activity. However in high doses it shows opioid activity such as euphoria and a morphine-like physical dependence after chronic administration. Its insolubility however, in aqueous solution prevents parenteral abuse. Nevertheless, diphenoxylate has in most countries been replaced by loperamide. 

Meperidine is commercially available in parenteral solutions for intravenous and intramuscular administration and in oral tablets and solution. 

In postoperative patients, a parenteral dose of 2-3 mg butorphanol produces analgesia and respiratory depression approximately equal to that produced by 10 mg morphine or 80-100 mg meperidine the onset, peak, and duration of action are similar to those that follow the administration of morphine. The plasma t of butorphanol is -3 hours, like pentazocine, analgesic doses of butorphanol produce an increase in pulmonary arterial pressure and in the work of the heart systemic arterial pressure is slightly decreased. 

Following subcutaneous or IM administration, onset of analgesia occurs within 10-15 minutes and peak effects occur within 1 hour [1,3]. Meperidine binds to both albumen and alpha-l-acid glycoprotein (AAG). The AAG level is dependent on the stress response and levels increase with trauma and infection. Further variability may be induced by eryrthocyte binding. Following intramuscular administration of meperidine the elimination half-life is 3.6 hours (3.1-4.1 hours). The average parenteral dose of meperidine is 1-1.5 mg/kg. 

Studies in rats have determined that subcutaneous doses of both meperidine and normeperidine lower the seizure threshold. In contrast, after intracerebro-ventricular (ICV) administration, meperidine raised the threshold while normeperidine lowered it. Naloxone antagonized this anticonvulsant effect of ICV-administered meperidine and enhanced the pro-convulsant effect of normeperidine. Neurotoxic symptoms can range from muscle twitching and jerking to full tonic-clonic seizures. Symptoms are worsened with parenteral doses approaching 1 g/day, in patients with underlying seizure disorders, pre-eclampsia, and acute renal failure. 

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