Gastric emptying time

FIGURE 1.6 In order to avoid extensive hepatic first-pass metabolism, nitroglycerin is given sublingually. GDN = 1,2- or 1.3-glyceryl dinitrate V.C. = vena cava. 

Drugs such as clindamycin and lincomycin should be taken on an empty stomach. Only 20 to 35% of clindamycin and lincomycin is absorbed from the gastrointestinal tract, and taking these agents with a meal further hinders their absorption and produces a plasma concentration of antibiotics that is ineffective. 

The tetracyclines should be taken orally 1 h before or 2 h after meals. Absorption of these agents is impaired by the presence of milk and milk products and by the concomitant administration of aluminum hydroxide gels, sodium bicarbonate, calcium and magnesium salts, or iron preparations because of the chelation of divalent and trivalent cations by these agents. 

Anticholingergic drugs such as propantheline should be taken 1 h before meals. Anticholinergic drugs are able to inhibit the secretion of gastric juice, which is ordinarily stimulated by food. 

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Most pancreatic enzyme supplements are enteric coated to release enzymes in the alkaline environment of the intestine this minimizes enzyme destruction in the stomach. Enteric-coated pancreatic enzyme supplements require fewer daily dosage units, but delivery of the drug to the site of action and effectiveness may be delayed by gastric emptying time.41... 

Levodopa, a dopamine precursor, is the most effective agent for PD. Patients experience a 40% to 50% improvement in motor function. It is absorbed in the small intestine and peaks in the plasma in 30 to 120 minutes. A stomach with excess acid, food, or anticholinergic medications will delay gastric emptying time and decrease the amount of levodopa absorbed. Antacids decrease stomach acidity and improve levodopa absorption. Levodopa requires active transport by a large, neutral amino acid transporter protein from the small intestine into the plasma and from the plasma across the blood-brain barrier into the brain (Fig. 29-2). Levodopa competes with other amino acids, such as those contained in food, for this transport mechanism. Thus, in advanced disease, adjusting the timing of protein-rich meals in relationship to levodopa doses may be helpful. Levodopa also binds to iron supplements and administration of these should be spaced by at least 2 hours from the levodopa dose.1,8,16,25... 

Fig. 8.2. Gastric emptying time for 50% fluid emptying, T5o in humans in various motility phases. Data from reference [57],...

Absorption/Distributton - Mexiletine is well absorbed (approximately 90%) from the Gl tract. The absorption rate is reduced in clinical situations (such as acute Ml) in which gastric emptying time is increased. 

Gastric ulcer Gastric ulcer may produce a delay in gastric emptying time and may complicate therapy (antral stasis). 

Song, Y. M., Sheu, W. H. H., and Lee, W. J. (2001). Acute biochemical variations induced by calcium citrate and calcium carbonate in Type 2 diabetic patients Impaired calcium absorption in Type 2 diabetic patients with prolonged gastric emptying time. /. Diabet. CompUc. 15, 97-102. 

Gastric emptying time Irregular Increased Slightly increased... 

E. To be approved, generic formulations must exhibit the same rate and extent of absorption as the trademark compound. All of the other choices can affect drug absorption. For example, slowing gastric emptying time may increase the absorption of a... 

Metoclopramide has antiemetic properties because it Accelerates gastric emptying time... 

Ovulation-related cyclicity Oral contraceptives or ERT Gastric emptying time Weight... 

Domperidone is structurally related to droperidol. It does not cross the blood-brain barrier to the same extent as droperidol so has fewer sedative side effects. It has an effect both on the CTZ and by a peripheral action on the stomach by increasing gastric emptying. Timing of the dose of drug is important for maximal efficacy. 

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