Pharmacokinetics Atenolol 50mg PO

Pharmacokinetics -- Atenolol 50mg PO

Description and mechanism of action

Atenolol is a medication which comes in 25 mg, 50 mg, and 100mg tablets. It is described as "a synthetic, beta1-selective (cardioselective) adrenoreceptor blocking agent, may be chemically described as [a] benzeneacetamide" (Drugs.com, 2011). Another website says it is "without intrinsic sympathomimetic and membrane stabilizing activity" (Ogbru, 2006). The drug was developed as a treatment for hypertension that was developed as a replacement for Propranolol (Healthline, 2011). The advantage of Atenolol over Propranolol is that it does not cross the blood-brain barrier, and thus it does not have as many central nervous system complications.

Pharmacokinetics

The drug is unable to be completely absorbed as it travels the gastrointestinal (GI) tract. "Approximately 50% of an oral dose is absorbed from the gastrointestinal tract, the remainder being excreted unchanged in the feces. Peak blood levels are reached between two (2) and four (4) hours after ingestion" (Drugs.com, 2011). The drug is absorbed rapidly and consistently, but incompletely. The portion that is available to the body then is fifty percent. Because the drug is not easily metabolized by the liver 85% of it is renally excreted when the drug is taken intravenously, versus 50% for the tablet. Only approximately 6% to 16% of the drug is bound to proteins in the plasma (MIS, 2004). According to Drugs.com (2011);

"The elimination half-life of oral atenolol is approximately 6 to 7 hours, and there is no alteration of the kinetic profile of the drug by chronic administration. Following intravenous administration, peak plasma levels are reached within 5 minutes. Declines from peak levels are rapid (5- to 10-fold) during the first 7 hours; thereafter, plasma levels decay with a half-life similar to that of orally administered drug."

The elimination of the drug is almost completely through via the kidneys and it is not affected by either dialysis or by liver problems.

Absorption and Contraindications

Since this is a medication for hypertension, there has not been very much research done in its use where certain populations are concerned. The route that the drug takes and the contraindications involved with regard to children are not known because there have not been enough child subjects use the drug to make these elements known (MIS, 2004). Men and women are the same with regard to how the drug affects them. Studies have shown the extreme effectiveness of Atenolol as "an effective antihypertensive agent providing 24-hour reduction of blood pressure" (Drugs.com, 2011). The drug can also be used in adults and the elderly as a hypertensive, and in cases of both angina pectoris and myocardial infarction. The contraindications for the adult group are for people whose systolic blood pressure is less than 100 mmHg or whose heart rate is below 50 beats per minute. The drug is indicated in these cases. It is necessary to be cautious when prescribing the drug to elderly populations. Although this group has more hypertension and the other problems for which Atenolol may be prescribed, it is necessary to watch that the systolic blood pressure especially when the patient is 60 years of age or older (Drugs.com). It is also necessary to note that;

"In general, elderly patients present higher atenolol plasma levels with total clearance values about 50% lower than younger subjects. The half-life is markedly longer in the elderly compared to younger subjects. The reduction in atenolol clearance follows the general trend that the elimination of renally excreted drugs is decreased with increasing age" (Drugs.com, 2011).