NIF-TEN CAPSULE

Atenolol
Nifedipine

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

1-p-Carbamoylmethylphenoxy-3-isopropylamino-2-propanol | 2-(p-(2-Hydroxy-3-(isopropylamino)propoxy)phenyl)acetamide | 4-(2-Hydroxy-3-((1-methylethyl)amino)propoxy)benzeneacetamide | Atenololum | Atenolol |

Description

A cardioselective beta-adrenergic blocker possessing properties and potency similar to propranolol, but without a negative inotropic effect.

Indication

For the management of hypertention and long-term management of patients with angina pectoris

Mechanism of Action

Like metoprolol, atenolol competes with sympathomimetic neurotransmitters such as catecholamines for binding at beta(1)-adrenergic receptors in the heart and vascular smooth muscle, inhibiting sympathetic stimulation. This results in a reduction in resting heart rate, cardiac output, systolic and diastolic blood pressure, and reflex orthostatic hypotension. Higher doses of atenolol also competitively block beta(2)-adrenergic responses in the bronchial and vascular smooth muscles.

Pharmacodynamics

Atenolol, a competitive beta(1)-selective adrenergic antagonist, has the lowest lipid solubility of this drug class. Although it is similar to metoprolol, atenolol differs from pindolol and propranolol in that it does not have intrinsic sympathomimetic properties or membrane-stabilizing activity. Atenolol is used alone or with chlorthalidone in the management of hypertension and edema.

Pharmacokinetics

Absorption:

Approximately 50% of an oral dose is absorbed from the gastrointestinal tract, the remainder being excreted unchanged in the feces.

Distribution:

Not Available

Metabolism:

Hepatic (minimal)

Elimination:

Approximately 50% of an oral dose is absorbed from the gastrointestinal tract, the remainder being excreted unchanged in the feces. Unlike propranolol or metoprolol, but like nadolol, atenolol undergoes little or no metabolism by the liver, and the absorbed portion is eliminated primarily by renal excretion.

Half-life

6-7 hours

Clearance

Not Available

Toxicity

LD50=2000-3000 mg/kg(orally in mice). Symptoms of an atenolol overdose include a slow heart beat, shortness of breath, fainting, dizziness, weakness, confusion, nausea, and vomiting.

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

4-(2'-Nitrophenyl)-2,6-dimethyl-1,4-dihydropyridin-3,5-dicarbonsaeuredimethylester | Adapine | Nifecard | Nifecor | Nifedipine | Nifedipino | Nifedipinum | Nifedipres | Nifedipine |

Description

Nifedipine has been formulated as both a long- and short-acting 1,4-dihydropyridine calcium channel blocker. It acts primarily on vascular smooth muscle cells by stabilizing voltage-gated L-type calcium channels in their inactive conformation. By inhibiting the influx of calcium in smooth muscle cells, nifedipine prevents calcium-dependent myocyte contraction and vasoconstriction. A second proposed mechanism for the drug’s vasodilatory effects involves pH-dependent inhibition of calcium influx via inhibition of smooth muscle carbonic anhydrase. Nifedipine is used to treat hypertension and chronic stable angina.

Indication

For the management of vasospastic angina, chronic stable angina, hypertension, and Raynaud's phenomenon. May be used as a first line agent for left ventricular hypertrophy and isolated systolic hypertension (long-acting agents).

Mechanism of Action

Nifedipine decreases arterial smooth muscle contractility and subsequent vasoconstriction by inhibiting the influx of calcium ions through L-type calcium channels. Calcium ions entering the cell through these channels bind to calmodulin. Calcium-bound calmodulin then binds to and activates myosin light chain kinase (MLCK). Activated MLCK catalyzes the phosphorylation of the regulatory light chain subunit of myosin, a key step in muscle contraction. Signal amplification is achieved by calcium-induced calcium release from the sarcoplasmic reticulum through ryanodine receptors. Inhibition of the initial influx of calcium inhibits the contractile processes of smooth muscle cells, causing dilation of the coronary and systemic arteries, increased oxygen delivery to the myocardial tissue, decreased total peripheral resistance, decreased systemic blood pressure, and decreased afterload. The vasodilatory effects of nifedipine result in an overall decrease in blood pressure.

Pharmacodynamics

Nifedipine, the prototype of the dihydropyridine class of calcium channel blockers (CCBs), is similar to other dihydropyridines including amlodipine, felodipine, isradipine, and nicardipine. There are at least five different types of calcium channels in Homo sapiens: L-, N-, P/Q-, R- and T-type. CCBs target L-type calcium channels, the major channel in muscle cells that mediates contraction. Similar to other DHP CCBs, nifedipine binds directly to inactive calcium channels stabilizing their inactive conformation. Since arterial smooth muscle depolarizations are longer in duration than cardiac muscle depolarizations, inactive channels are more prevalent in smooth muscle cells. Alternative splicing of the alpha-1 subunit of the channel gives nifedipine additional arterial selectivity. At therapeutic sub-toxic concentrations, nifedipine has little effect on cardiac myocytes and conduction cells. By blocking the calcium channels, Nifedipine inhibits the spasm of the coronary artery and dilates the systemic arteries, results in a increase of myocardial oxygen supply and a decrease in systemic blood pressure.

Pharmacokinetics

Absorption:

Rapidly and fully absorbed following oral administration.

Distribution:

Not Available

Metabolism:

Hepatic metabolism via cytochrome P450 system. Predominantly metabolized by CYP3A4, but also by CYP1A2 and CYP2A6 isozymes.

Elimination:

Nifedipine is extensively metabolized to highly water-soluble, inactive metabolites accounting for 60 to 80% of the dose excreted in the urine. The remainder is excreted in the feces in metabolized form, most likely as a result of biliary excretion.

Half-life

2 hours

Clearance

Not Available

Toxicity

Symptoms of overdose include dizziness, drowsiness, nausea, severe drop in blood pressure, slurred speech, and weakness. LD50=494 mg/kg (orally in mice); LD50=1022 mg/kg (orally in rats)

References

  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank

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Approval Information

NIF-TEN CAPSULE was registered with Health Science Authority of Singapore by ASTRAZENECA SINGAPORE PTE LTD. It is marketed with the registration number of SIN00798P with effective from 1988-06-05.

This product contains 50mg of Atenolol, and 20mg of Nifedipine in the form of CAPSULE.

The medicine was manufactured by Corden Pharma GmbH in GERMANY

It is a Presciption Only Medicine which can only be obtained from a doctor or a dentist, or from a pharmacist with a prescription from a Singapore-registered doctor or dentist.

Anatomical Therapeutic Chemical (ATC) Classification

ATC Code: C08CA55

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