Atenolol is available in the form of 25, 50, and 100mg oraltablets.[21][4] It is also available in the form of oral tablets containing a combination of 50 or 100mg atenolol and 50mg chlortalidone.[21] Atenolol was previously available in a 0.5mg/mL solution for injection as well, but this formulation was discontinued.[21]
Hypertension treated with a β-blocker such as atenolol, alone or in conjunction with a thiazide diuretic, is associated with a higher incidence of new onset type 2 diabetes mellitus compared to those treated with an ACE inhibitor or angiotensin receptor blocker.[22][23]
β-blockers, of which atenolol is mainly studied, provides weaker protection against stroke and mortality in patients over 60 years old compared to other antihypertensive medications.[24][25][26][18]Diuretics may be associated with better cardiovascular and cerebrovascular outcomes than β-blockers in the elderly.[27]
Rarely, atenolol has been associated with induction of acute delirium.[28][2][29]
Overdose
Symptoms of overdose are due to excessive pharmacodynamic actions on β1 and also β2-receptors. These include bradycardia (slow heartbeat), severe hypotension with shock, acute heart failure, hypoglycemia and bronchospastic reactions. Treatment is largely symptomatic. Hospitalization and intensive monitoring is indicated. Activated charcoal is useful to absorb the drug. Atropine will counteract bradycardia, glucagon helps with hypoglycemia, dobutamine can be given against hypotension and the inhalation of a β2-mimetic such as hexoprenalin or salbutamol will terminate bronchospasms. Blood or plasma atenolol concentrations may be measured to confirm a diagnosis of poisoning in hospitalized patients or to assist in a medicolegal death investigation. Plasma levels are usually less than 3 mg/L during therapeutic administration, but can range from 3–30 mg/L in overdose victims.[30][31]
The beta-blocking effects of atenolol, as measured by reduction of exercise-related tachycardia, are apparent within 1hour and are maximal within 2 to 4hours following a single oral dose.[4] The general effects of atenolol, including beta-blocking and antihypertensive effects, last for at least 24hours following oral doses of 50 or 100mg.[4] With intravenous administration, maximal reduction in exercise-related tachycardia occurs within 5minutes and following a single 10mg dose has dissipated within 12hours.[4] The duration of action of atenolol is dose-related and is correlated with circulating levels of atenolol.[4]
Pharmacokinetics
Absorption
The oralbioavailability of atenolol is approximately 50 to 60%.[2][3] The absorption of atenolol with oral administration is rapid and consistent but is incomplete.[4] About 50% of an oral dose of atenolol is absorbed from the intestines, with the rest excreted in feces.[4]Maximal concentrations of atenolol occur 2 to 4hours following an oral dose, whereas peak concentrations occur within 5minutes with intravenous administration.[4] The pharmacokinetic profile of atenolol results in it having relatively consistent plasma drug levels with about 4-fold variation between individuals.[4]
Atenolol is classified as a beta blocker with low lipophilicity and hence lower potential for crossing the blood–brain barrier and entering the brain.[44] This in turn may result in fewer effects in the central nervous system as well as a lower risk of neuropsychiatric side effects.[44] Only small amounts of atenolol are said to enter the brain.[2][3] The brain-to-blood ratio of atenolol was 0.2 : 1 in one study, whereas the ratio for propranolol was 33 : 1 in the same study.[3]
Metabolism
Atenolol undergoes minimal or negligible metabolism by the liver.[4][5] It has been estimated that about 5% of atenolol is metabolized.[6] This is in contrast to other beta blockers like propranolol and metoprolol, but is similar to nadolol.[4] In accordance with its lack of hepatic metabolism, the pharmacokinetics of atenolol are not altered in hepatic impairment, unlike the case of propranolol.[5] Two metabolites of atenolol have been identified: hydroxyatenolol and atenolol glucuronide.[2] It has been said that it is unknown if these metabolites are active.[2] However, another source stated that hydroxyatenolol has one-tenth the beta-blocking activity of atenolol.[3]
Elimination
Instead of by hepatic metabolism, atenolol is eliminated from the blood mainly via renalexcretion.[4] Atenolol is excreted about 40 to 50% in urine and 50% in feces with oral administration.[3][4] Conversely, it is excreted 85 to 100% in urine unchanged and 10% in feces with intravenous administration.[3][4] Only very small amounts of hydroxyatenolol and atenolol glucuronide are found in urine with atenolol.[3]
The elimination half-life of atenolol is about 6 to 7hours.[4] The half-life of atenolol does not change with continuous administration.[4] With intravenous administration, atenolol levels rapidly decline (5- to 10-fold) during the first 7hours and thereafter decline at a rate similar to that with oral administration.[4]
The elimination of atenolol is slowed in renal impairment, with the elimination rate being closely related to the glomerular filtration rate (GFR) and with significant accumulation occurring when the creatinineclearance rate is under 35mL/min/1.73m2.[4] At a GFR of less than 10mL/min, the half-life of atenolol increases up to 36hours.[6]
Atenolol has been given as an example of how slow healthcare providers are to change their prescribing practices in the face of medical evidence that indicates that a drug is not as effective as others in treating some conditions.[48] In 2012, 33.8 million prescriptions were written to American patients for this drug.[48] In 2014, it was in the top (most common) 1% of drugs prescribed to Medicare patients.[48] Although the number of prescriptions has been declining steadily since limited evidence articles contesting its efficacy was published, it has been estimated that it would take 20 years for doctors to stop prescribing it for hypertension.[48] Despite its diminished efficacy when compared to newer antihypertensive drugs, atenolol and other beta blockers are still a relevant clinical choice for treating some conditions, since beta blockers are a diverse group of medicines with different properties that still requires further research.[18] As consequence, reasons for the popularity of beta blockers cannot be fully attributed to a slow healthcare system – patient compliance factor, such as treatment cost and duration, also affect adherence and popularity of therapy.[49]
^ abcdefWadworth AN, Murdoch D, Brogden RN (September 1991). "Atenolol. A reappraisal of its pharmacological properties and therapeutic use in cardiovascular disorders". Drugs. 42 (3): 468–510. doi:10.2165/00003495-199142030-00007. PMID1720383.
^ abcdefghijklHeel RC, Brogden RN, Speight TM, Avery GS (June 1979). "Atenolol: a review of its pharmacological properties and therapeutic efficacy in angina pectoris and hypertension". Drugs. 17 (6): 425–460. doi:10.2165/00003495-197917060-00001. PMID38096.
^ abcdefBrodde OE, Kroemer HK (2003). "Drug-drug interactions of beta-adrenoceptor blockers". Arzneimittelforschung. 53 (12): 814–822. doi:10.1055/s-0031-1299835. PMID14732961. Atenolol is only minimally, if at all, metabolized and renally excreted in mostly unchanged form; thus an interaction with drugs that interfere with the hepatic metabolism is not to be expected. It is also very unlikely that the genetic polymorphisms of the CYP-family might affect the pharmacokinetics of atenolol. In fact it has been shown that plasma concentrations of nonmetabolized atenolol was not significantly different between "extensive" and "poor debrisoquine metabolizers" – in contrast to the plasma concentrations of metoprolol that were significantly increased in "poor metabolizers" (Dayer et al. 1985, Lewis et al. 1985). Furthermore, in healthy volunteers cimetidine (CAS 70059- 30-2) did not affect plasma concentrations of atenolol but significantly increased plasma concentrations of metoprolol or propranolol (Kirch et al. 1981).
^ abcKirch W, Görg KG (1982). "Clinical pharmacokinetics of atenolol--a review". Eur J Drug Metab Pharmacokinet. 7 (2): 81–91. doi:10.1007/BF03188723. PMID6749509.
^World Health Organization (2021). World Health Organization model list of essential medicines: 22nd list (2021). Geneva: World Health Organization. hdl:10665/345533. WHO/MHP/HPS/EML/2021.02.
^Rehman B, Sanchez DP, Shah S (2021). "Atenolol". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID30969666. Archived from the original on 10 October 2022. Retrieved 5 September 2021.
^"Atenolol". The American Society of Health-System Pharmacists. Archived from the original on 18 April 2019. Retrieved 8 May 2018.
^ abcWiysonge CS, Bradley HA, Volmink J, Mayosi BM, Opie LH (January 2017). "Beta-blockers for hypertension". The Cochrane Database of Systematic Reviews. 1 (1): CD002003. doi:10.1002/14651858.CD002003.pub5. PMC5369873. PMID28107561. Further research should be of high quality and should explore whether there are differences between different subtypes of beta-blockers or whether beta-blockers have differential effects on younger and older people [...] Beta-blockers were not as good at preventing the number of deaths, strokes, and heart attacks as other classes of medicines such as diuretics, calcium-channel blockers, and renin-angiotensin system inhibitors. Most of these findings come from one type of beta-blocker called atenolol. However, beta-blockers are a diverse group of medicines with different properties, and we need more well-conducted research in this area." (p. 2-3)
^Lindholm LH, Carlberg B, Samuelsson O (October 2005). "Should β blockers remain first choice in the treatment of primary hypertension? A meta-analysis". The Lancet. 366 (9496): 1545–1553. doi:10.1016/S0140-6736(05)67573-3. PMID16257341. S2CID34364430.
^Messerli FH, Grossman E, Goldbourt U (June 1998). "Are beta-blockers efficacious as first-line therapy for hypertension in the elderly? A systematic review". JAMA. 279 (23): 1903–7. doi:10.1001/jama.279.23.1903. PMID9634263.
^ abScheen AJ (September 2011). "Cytochrome P450-mediated cardiovascular drug interactions". Expert Opin Drug Metab Toxicol. 7 (9): 1065–1082. doi:10.1517/17425255.2011.586337. PMID21810031. β-Blockers still represent widely prescribed drugs as they cover a wide spectrum of CV indications. Obviously, it is not trivial which β-blocker to choose as they differ both with regard to their PD and PK profiles [82]. It is well known when comparing the characteristics of atenolol, bisoprolol, metoprolol (each β-1 selective) and carvedilol (β-1 and β-2 nonselective). Among these β-blockers, atenolol is mainly eliminated by renal excretion; bisoprolol is in part excreted as parent compound via the renal route (50%); the other 50% are hepatically metabolized; whereas metoprolol and carvedilol are metabolized by CYP2D6. DDIs are mainly observed with those β-blockers that are metabolized via CYP enzymes. However, it should be emphasized that, in general, β-blockers are well-tolerated safe drugs with a large therapeutic index [83].
^Richards JR, Albertson TE, Derlet RW, Lange RA, Olson KR, Horowitz BZ (May 2015). "Treatment of toxicity from amphetamines, related derivatives, and analogues: a systematic clinical review". Drug Alcohol Depend. 150: 1–13. doi:10.1016/j.drugalcdep.2015.01.040. PMID25724076.
^Vetter VL, Elia J, Erickson C, Berger S, Blum N, Uzark K, et al. (May 2008). "Cardiovascular monitoring of children and adolescents with heart disease receiving medications for attention deficit/hyperactivity disorder [corrected]: a scientific statement from the American Heart Association Council on Cardiovascular Disease in the Young Congenital Cardiac Defects Committee and the Council on Cardiovascular Nursing". Circulation. 117 (18): 2407–2423. doi:10.1161/CIRCULATIONAHA.107.189473. PMID18427125. Amphetamines (Adderall, Dexedrine): Electrophysiological Effects of Amphetamines: Amphetamines have been associated with tachyarrhythmias and sudden death.113–115 Many of the electrophysiological effects of amphetamines may be initiated by the release of norepinephrine stores from presynaptic vesicles and blocking of norepinephrine reuptake.116,117 In addition, amphetamines are potent blockers of dopamine uptake and strong central nervous system stimulants. Dopaminergic Effects of Amphetamines: In addition to the β-agonist effects of amphetamines, the dopamine receptors D1 and D2 contribute to the cardiovascular effects of methamphetamine by producing a pressor response accounting for the increase in blood pressure. The D1 receptor also is involved in mediating the positive tachycardic effects of methamphetamine.117
^Mores N, Campia U, Navarra P, Cardillo C, Preziosi P (June 1999). "No cardiovascular effects of single-dose pseudoephedrine in patients with essential hypertension treated with beta-blockers". Eur J Clin Pharmacol. 55 (4): 251–254. doi:10.1007/s002280050624. PMID10424315.
^Hassan NA, Gunaid AA, El-Khally FM, Al-Noami MY, Murray-Lyon IM (April 2005). "Khat chewing and arterial blood pressure. A randomized controlled clinical trial of alpha-1 and selective beta-1 adrenoceptor blockade". Saudi Med J. 26 (4): 537–541. PMID15900355.
^O'Connell MB, Gross CR (1990). "The effect of single-dose phenylpropanolamine on blood pressure in patients with hypertension controlled by beta blockers". Pharmacotherapy. 10 (2): 85–91. doi:10.1002/j.1875-9114.1990.tb02554.x. PMID2349137.
^O'Connell MB, Gross CR (1991). "The effect of multiple doses of phenylpropanolamine on the blood pressure of patients whose hypertension was controlled with beta blockers". Pharmacotherapy. 11 (5): 376–81. doi:10.1002/j.1875-9114.1991.tb02648.x. PMID1684039.
^ abGadde KM, Krishnan KR (1998). "Management of Side Effects of Monoamine Oxidase Inhibitors". In Balon R (ed.). Practical Management of the Side Effects of Psychotropic Drugs. Medical Psychiatry Series. CRC Press. pp. 67–83 (71). ISBN978-0-8247-4630-8. Retrieved 8 July 2024. Interestingly, in one study, orthostatic hypotension was eliminated in a group of 61 patients treated for migraine headaches with phenelzine, when a beta-blocker, atenolol, was added (15). The authors have reported that hypertensive reactions were also less frequent when the two drugs were combined. We need further experience with this combination to determine whether addition of a beta-blocker is a safe and an effective strategy for alleviation of postural hypotension in depressed patients receiving an MAOI.
^O'Brien P, Oyebode F (2003). "Psychotropic medication and the heart". Advances in Psychiatric Treatment. 9 (6): 414–423. doi:10.1192/apt.9.6.414. ISSN1355-5146. Postural hypotension is also a risk when antipsychotics are taken with β-blockers (probably because of pharmacokinetic interaction) or with diuretics (because of Na+ or volume depletion). The same hypotensive effects might be anticipated when tricyclic antidepressants or MAOIs are co-prescribed with peripheral antihypertensive agonists. One possible exception concerns phenelzine, whose hypotensive action was reversed on co-therapy with atenolol (Merikangas & Merikangas, 1995).