Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2020 Publisher: Omega Pharma Ltd., 1st Floor, 32 Vauxhall Bridge Road, LONDON, SW1V 2SA, United Kingdom
Pharmacotherapeutic classification: N07BA01 (Anti-smoking agents: N07BA, Nicotine 01)
Nicotine, the chief alkaloid in tobacco products and a naturally occurring autonomic drug, is an agonist at nicotine receptors in the peripheral and central nervous system and has pronounced CNS and cardiovascular effects. Withdrawal from nicotine in addicted individuals is characterised by craving, nervousness, restlessness, irritability, mood lability, anxiety, drowsiness, sleep disturbances, impaired concentration, increased appetite, minor somatic complaints (headache, myalgia, constipation, fatigue) and weight gain. Withdrawal symptoms, such as cigarette craving, may be controlled in some individuals by steady-state plasma levels lower than those for smoking.
In clinically controlled trials, NiQuitin was shown to alleviate nicotine withdrawal symptoms as well as craving. NiQuitin reduced the severity of cravings by at least 35% at all times of day during the first two weeks of abstinence, compared to placebo (p<0.05).
Following transdermal application, the skin rapidly absorbs nicotine released initially from the patch adhesive. The plasma concentrations of nicotine reach a plateau within 2-4 hours after initial application of NiQuitin with relatively constant plasma concentrations persisting for 24 hours or until the patch is removed. Approximately 68% of the nicotine released from the patch enters systemic circulation and the remainder of the released nicotine is lost via vaporisation from the edge of the patch.
With continuous daily application of NiQuitin (worn for 24 hours), dose-dependent steady state plasma nicotine concentrations are achieved following the second NiQuitin application and are maintained throughout the day. These steady state maximum concentrations are approximately 30% higher than those following a single application of NiQuitin.
Plasma concentrations of nicotine are proportional to dose for the three dosage forms of NiQuitin. The mean plasma steady state concentrations of nicotine are approximately 17ng/ml for the 21mg/day patch, 12ng/ml for the 14mg /day patch and 6ng/ml for the 7mg/day patch. For comparison, half-hourly smoking of cigarettes produces average plasma concentrations of approximately 44ng/ml.
The pronounced early peak in nicotine blood levels seen with inhalation of cigarette smoke is not observed with NiQuitin.
Following removal of NiQuitin, plasma nicotine concentrations decline with an apparent mean half-life of 3 hours, compared with 2 hours for IV administration due to continued absorption of nicotine from the skin depot. If NiQuitin is removed most non-smoking patients will have non-detectable nicotine concentrations in 10 to 12 hours.
A dose of radiolabelled nicotine given intravenously showed a distribution of radioactivity corresponding to the blood supply with no organ selectively taking up nicotine. The volume of distribution of nicotine is approximately 2.5l/kg.
The major elimination organ is the liver and average plasma clearance is about 1.2 l/min; the kidney and the lung also metabolise nicotine. More than 20 metabolites of nicotine have been identified, all of which are believed to be pharmacologically inactive. The principal metabolites are cotinine and trans-3-hydroxycotinine. Steady state plasma cotinine concentrations exceed nicotine by 10-fold. The half-life of nicotine ranges from 1 to 2 hours and cotinine’s between 15 and 20 hours.
Both nicotine and its metabolites are excreted through the kidneys and about 10% of nicotine is excreted unchanged in the urine. As much as 30% may be excreted in the urine with maximum flow rates and extreme urine acidification (pH≤5).
There were no differences in nicotine kinetics between men and women using NiQuitin. Obese men using NiQuitin had significantly lower AUC and Cmax values compared with normal weight men. Linear regression of AUC vs total body weight showed the expected inverse relationship (AUC decreases as weight increases). Nicotine kinetics were similar for all sites of application on the upper body and upper outer arm.
The general toxicity of nicotine is well known and taken into account in the recommended posology. Nicotine was not mutagenic in appropriate assays. The results of carcinogenicity assays did not provide any clear evidence of a tumorigenic effect of nicotine. In studies in pregnant animals, nicotine showed maternal toxicity, and consequential mild fetal toxicity. Additional effects included pre- and postnatal growth retardation and delays and changes in postnatal CNS development.
Studies in male rats have shown that nicotine can decrease testis weight, cause a reversible decrease in Sertoli cell numbers with impairment of spermatogenesis, and result in a variety of changes in the epididymis and vas deferens. However, similar effects have not been reported to occur in humans.
Effects were only noted following exposure to nicotine at levels in excess of those which will result from recommended use of NiQuitin.
Comparison of the systemic exposure necessary to elicit these adverse responses from preclinical test systems with that associated with the recommended use of NiQuitin indicate that the potential risk is low and outweighed by the demonstrable benefit of nicotine therapy in smoking cessation. However, NiQuitin should only be used by pregnant women on medical advice if other forms of treatment have failed.
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