Enteral administration dose-forms

Input functions [i.e., I(t)], describing the rate at which the administered dose enters a compartment, may have various forms depending on the administration schedule. The input function /(f) is added to the appropriate mass balance equation and can describe any drug administration pattern. First-order absorption... 

Alternative options are increasingly favoured in the form of oral iron polymaltose complexes. These are more expensive but attractive in that complications are less frequently encountered and the lethal toxicity that follows release of large amounts or ionic iron into the circulation does not occur. Carbonyl iron is not often used but available in some countries. In contrast combinations with vitamins and cobalt, still popular in certain areas, have no documented advantage and add quite unnecessary cost. Other routes are intramuscular injections and, except where oral administration is precluded, have disadvantages in that mobilization is unpredictable. Conversely, it is feasible to replace iron as a single total dose infusion but such procedures need to be given under supervised conditions. It is reiterated that the rate of rise in haemoglobin that follows adequate oral replacement is comparable to that achieved par-enterally. 

Acute lead-poisoning is by no means of as common occurrence aa the chronic form, and usually terminates in recovery. It is caused by the ingestion of a single large dose of the acetate, eubacetate, carbonate, ct of red lead. In such cases the administration of magnesium sulplmte is indicated it enters into double decomposition with the Pb salt to form the insoluble PbSO,. 

Tellurium excretion patterns depend on the chemical forms and mode of administration of the compounds. Parenterally administered tellurium is excreted mainly in the urine rather than the feces, whereas orally ingested tellurium salts are excreted mainly in the feces (Durbin 1960). After oral dosing to rats, 60 -80% of ingested tellurite is rapidly excreted in the feces. The absorbed tellurium is secreted in the bile and enters the intestine. Small amounts of absorbed elemental tellurium and tellurite are exhaled ( 0.1%) presumably as dime-thyltelluride, and produce a characteristic garlic-like breath odor (De Meio 1946). 

After oral administration, intestinal absorption of the statins varies between 30% and 85%. All of the statins, except simvastatin and lovastatin, are administered as active ffhydroxy acids. Simvastatin and lovastatin are administered as inactive lactones that must be transformed in the liver to their respective ffhydroxy acids. There is extensive first-pass hepatic uptake of all statins, but they enter the liver by different mechanisms. Uptake of atorvastatin, pravastatin, and rosuvastatin is mediated by the organic anion transporter 2 (OATP2). The lipophilic lactone forms of simvastatin and lovastatin are thought to enter the liver by simple diffusion. Due to extensive first-pass hepatic uptake, systemic bioavailability of the statins and their hepatic metabolites varies between 5% and 30% of administered doses. Except for fluvastatin and pravastatin, the metabolites of all statins have some HMG-CoA reductase inhibitory activity. Under steady-state conditions, small amounts of the parent drug and its metabolites produced in the liver can be found in the systemic circulation. In the plasma, >95% of statins and their metabolites are protein bound with the exception of pravastatin and its metabolites (50% bound). 

Chloroquine phosphate (aralen) is available for oral administration. Adults take 500 mg chloro-quine phosphate (300 mg base) weekly starting 1-2 weeks before entering an endemic area and continuing for 4 weeks after leaving. The pediatric dosage is 8.3 mg/kg chloroquine phosphate (5 mg base per kg, up to the maximum adult dose) taken orally by the same schedule. Note Primaquine phosphate is used to eradicate latent tissue forms of P. vivax and P. ovale and effect a radical cure after individuals leave areas endemic for these infections see Table 39-2 and text). 

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