Stomach emptying rate

Solubility Stomach emptying rate Dissolution rate... 

Drug release and retention at the site of absorption are very important for the enhancement of the bioavailability, particularly when the absorption sites are localized to a certain area of the GI route. This control of the transition of the drug can be achieved using bioadhesive excipients. Chlorothiazide (CT), a diuretic and antihypertensive drug, was better orally absorbed when administered with mucoadhesive polymers [25], The absorption of CT is considered to be saturable and site-specific, because a low dose is better absorbed, and a decreased stomach emptying rate and slow GI transition rate are better for increased absorption. As chitosan is a mucoadhesive polymer, the absorption of CT is expected to be enhanced... 

A drug in a suspension is in solid form, but is finely divided and has a large surface area. Drug particles can diffuse readily between the stomach and small intestine so that absorption is relatively insensitive to stomach emptying rate. 

Vehicle-dependent effects are relevant not only because solvents and suspending agents allow delivery of higher concentrations, but also because the choice of vehicle can alter absorption rate. This may be related to decreased stomach emptying rate (for vegetable oils) or altered partitioning among fluid phases in the GI tract and across the epithelial cell membranes. Lipophilic compounds dissolved in oil will not be absorbed until the oil phase is acted upon by bile salts, converted to chylomicrons, and absorbed. If the compounds are dissolved or suspended in water, they may partition much more rapidly into cells this may be facilitated by rapid absorption of a water-miscible solvent such as alcohol or DMSO. 

In summary, food will delay stomach emptying and, as a result, may decrease the rate of availability of a drug from its oral dosage form. The extent of availability of that drug, however, may be increased, decreased, or unaffected by meals. Thus, it is important for the pharmacist to counsel patients on the importance of timing the taking of their medications relative to their mealtimes. 

Usually, an increase in Cg that would affect the dissolution rate would occur only when another process, such as membrane transport or stomach emptying, becomes the rate-limiting step in drug absorption. As a general rule pharmacists should advise patients to take their oral medications with a full glass of water to ensure that dissolution occurs under optimal conditions. 

Thus, it was suggested that pectin may moderate the glucose (and hence the insulin) response by delaying the rate at which stomach emptying occurs. 

The intestinal phase, which occurs as chyme enters the duodenum. This involves many inhibitory controls neural and endocrine mechanisms limit the rate of stomach emptying so that the secretory and absorptive mechanisms of the small intestine can cope effectively with the entry of gastric contents. 

Gastrointestinal 1 secretions J, rate of stomach emptying J, rate of intestinal transit time J, liver volume and blood flow... 

The stomach empties liquids faster than solids. The rate of transfer of gastric contents to the small intestine is retarded by the activity of receptors sensitive to acid, fat, osmotic pressure and amino acids in the duodenum and the small intestine and stimulated by material that has arrived from the stomach. Gastric emptying is a simple exponential or square-root function of the volume of a test meal - a pattern that holds for meals of variable viscosity. To explain the effect of a large range of substances on emptying, an osmoreceptor has been postulated which, like a red blood cell, shrinks in hypertonic solutions and swells in hypotonic solutions. 

If one observes animals on a diet with a high concentration of browned materials, one immediately notes that almost all of the animals have severe diarrhea. It is also obvious on further examination that animals on the diet develop enlarged cecums. Another observed effect upon the digestive system of animals is the increase in the excretion of essential and nonessential amino acids in the form of short peptides, 4-6 residues long, in the feces. Coupled with this, the fecal nitrogen content is approximately 35% above the control, possibly relating to the existence of diarrhea and the decrease in the rate of stomach emptying (33). 

Since most drugs are largely absorbed in the upper part of the small intestine, drugs that alter the rate at which the stomach empties can affect absorption. Propantheline, for example, delays gastric emptying and reduces paracetamol (acetaminophen) absorption, (p.l92), whereas metoclopra-mide , (p.l91), has the opposite effect. However, the total amount of drug absorbed remains unaltered. Propantheline also increases the absorption of hydrochlorothiazide , (p.959). Drugs with antimuscarinic effects decrease the motility of the gut, thus the tricyclic antidepressants can increase the absorption of dicoumarol , (p.457), probably because they... 

Propantheline 30 mg intravenously delayed the peak serum levels of paracetamol 1.5 g in 6 convalescent patients from about 1 hour to 3 hours. Peak levels were lowered by about one-third, but the total amount of paracetamol absorbed was unchanged. This effect occurs because propantheline is an antimuscarinic drug that slows the rate at which the stomach empties, so that the rate of absorption in the gut is reduced. The practical consequence of this is likely to be that rapid pain relief with single doses of paracetamol may be delayed and reduced by antimuscarinics (see Table 18. r, (p.672), and Table 18.2 , (p.674) for a list) but this needs clinical confirmation. If the paracetamol is being taken in repeated doses over extended periods this seems unlikely to be an important interaction because the total amount absorbed is unchanged. 

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