Dosage forms rectal administration

In the request for a pharmacy preparation, the physician often prescribes the administration route. Pharmacists have to critically evaluate whether the proposed route is appropriate to reach the desired bioavailability. For example, conventional oral medications may not be suitable for patients with a nasogastric feeding tube, children, or nauseous patients and alternative routes such as parenteral, rectal, or nasal have to be considered (see also Sect. 37.6.3). When adapting a dosage form or administration route to special needs of a patient, the pharmacist is required to consider safety aspects. It is important to recognise that an active substance approved for oral administration may never have... 

Rectal Administration. The administration of drugs by a solid rectal dosage form (i.e., suppositories) results in a wide variability in the rate and extent of absorption in children [79]. This fact, coupled with the inflexibility of a fixed dose, makes this a route that should not be promoted for pediatric patients. At least one death involving a 7-month-old infant can be directly attributed to the use of solid rectal dosage form of a therapeutic dose of morphine [80]. 

Drugs are administrated by intravenous routes or ex-travascular routes including oral, sublingual, subcutaneous, intramuscular, rectal (by enema or suppository), and transdermal. Available dosage forms include suspensions, immediate-release capsules or tablets, sustained-release capsules or tablets, and enteric-coated capsules or tablets that resist dissolution in the acidic pfi of the stomach. 

Suppositories are pharmaceutical dosage forms intended for administration of medicine via the rectum, vagina, or urethra that melt, soften, or dissolve in the body cavity. Rectal and vaginal suppositories are most common but urethral suppositories are sometimes used. Suppositories are indicated for administering drugs to infants and small children, severely debilitated patients, those who cannot take medications orally, and those for whom the parenteral route might be unsuitable. Suppositories are used to administer drugs for either systemic or local application. Local applications include the... 

Softgel capsules have gained popularity and use in the pharmaceutical industry for human and veterinary use, as an oral dosage form, as suppositories for rectal and vaginal administration, single... 

In certain areas of the world, particularly some European countries and Japan, rectal dosage forms are somewhat more accepted by the patient population and, hence, development of rectal dosage forms has surpassed that in the United States. According to a survey in 1970, approximately 7.5% of all prescriptions in France were formulations intended for rectal administration.Even though a few countries may find rectal dosage forms more acceptable, these still represent a small area of the world-wide market share which can be assigned to rectal drug therapy. 

There are at least two common problems that can lead to drug loss following rectal administration. First, for effective absorption, the dosage form must be retained in the rectum. Thus if the dosage form or parts thereof are lost prematurely from the rectum, drug absorption will be substantially reduced. A study with children showed that when thiopentone suppositories were voided within 40 min, an effective plasma level was maintained for less than 2 h, whereas when the suppositories were retained, an effective level was maintained for about 24 h. 

As discussed earlier, the pH of the rectal fluid can have a marked effect on the absorption of drugs from the rectum. Since the rectal fluid has a relatively low buffering capacity and the volume of the rectal fluid is small, it might be expected that the contents of the rectal dosage form largely control the pH of the rectum during administration. On this basis, one may be able to utilize the pH characteristics of the drug and incorporate suitable buffers and other excipients in the... 

The most common route of exposure to the shortacting barbiturates is ingestion of oral dosage forms. Several of these agents are also available for parenteral administration (intramuscular or intravenous) and have been used as rectal suppositories. 

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