Nifedipine

BRAND NAMES:

Adipine – It contains nifedipine's active component. It can be purchased as a pill to treat high blood pressure.

Coracten – It has nifedipine's active components. It is sold as capsules and is used to treat hypertension and chronic stable angina pectoris. 

Fortipine – It has nifedipine as its active component. It is offered as pills that are intended to manage angina symptoms.

MECHANISM OF ACTION:

During the depolarisation phase of smooth muscle cells, calcium ions flow through voltage-gated channels. Nifedipine limits calcium ion entrance by blocking voltage-dependent al-type calcium channels in vascular smooth muscle and cardiac cells. Reduced intracellular calcium lowers peripheral arterial vascular resistance and dilates coronary arteries, lowering systemic blood pressure and increasing myocardial oxygen delivery. Nefidipine has both hypotensive and antianginal effects.

PHARMACOKINETICS:

Absorption: It is virtually entirely absorbed in the gastrointestinal tract, however, its bioavailability ranges between 45 and 68%, which is related to first-pass metabolism. 

Distribution: The steady-state volume of distribution for nifedipine is 0.62-0.77L/kg, whereas the volume of distribution for the central compartment is 0.25-029L/kg. 

Metabolism: Nifedipine is primarily metabolized by CYP3A4. Nifedipine is primarily metabolized into 2,6-dimethyl-4-(2-nitrophenyl)-5-methoxycarbonyl-pyridine-3-carboxylic acid, which is then converted to 2-hydroxymet l-pyridine carboxylic acid. Nifedipine is also partially metabolized into dehydronifedipine.

Excretion: Nifedipine is retrieved in the urine as inactive water-soluble metabolites, with the remaining metabolites excreted in the feces. 

PHARMACODYNAMICS:

Immediate-release nifedipine has a duration of action that requires three doses each day. It is often dosed at 10-120mg per day. It inhibits L-type voltage-gated calcium channels, lowering blood pressure and increasing oxygen delivery to the heart. 

DOSAGE AND ADMINISTRATION:

For oral use, nifedipine is available as an extended-release tablet and capsule. Usually, the capsules should be taken three or four times a day. Once daily, on an empty stomach, the extended-release tablet should be taken one hour before or two hours after eating.

•        It is available in capsules with the strength of 10mg and 20mg.

•        Extended-release oral tablet with the strength of 30mg, 60mg, and 90mg.

DRUG INTERACTIONS:

Drug interactions with nifedipine may include 

• Anti-cancer drugs – quinidine
• Anti-epileptic medicine – phenytoin
• Anti-tuberculosis – rifampicin
• Antibiotics – erythromycin
• Anti-HIV drugs – ritonavir, nelfinavir
• Anxiety drugs - phenobarbital

CONTRAINDICATIONS:

Absolute contraindications of nifedipine are hypersensitivity to nifedipine or its components and DT-elevation myocardial infarction

Relative contraindications of nifedipine are severe aortic stenosis, unstable angina, hypotension, heart failure, and moderate to severe hepatic impairment. 

SIDE EFFECTS:

Nifedipine may cause side effects may include

• Headache
• Nausea
• Dizziness
• Flushing
• Heartburn
• Muscle cramps
• Constipation
• Cough
• Decreased sexual ability

Some serious side effects of nifedipine may include

• Swelling of the eye, face, lips
• Difficulty breathing
• Fainting
• Rash
• Yellowing of the skin
• Severity of chest pain

 OVERDOSE:

Symptoms of overdose may include 

• Dizziness
• Fast heartbeat
• Flushing
• Nervousness
• Nausea
• Vomiting
• Swelling of the hands, feet, ankles, or lower legs.
• Blurred vision
• fainting

TOXICITY:

There is no specific antidote. Overdose treatment varies according to the amount ingested, the length after ingestion, the patient's age, and any co-morbidities. The initial assessment includes securing the airway, breathing, and circulation, as well as performing proper blood tests, including constant testing. An overdose of nifedipine can result in systemic vasodilation, severe hypotension, and reflux tachycardia. Prolonged systemic hypotension might lead to shock or even death.