Extendryl HC

Uses

Guaifenesin is an expectorant commonly found in OTC products for the symptomatic relief from congested chests and coughs associated with cold, bronchitis, and/or other breathing illnesses.

Guaifenesin is an expectorant that is indicated for providing temporary symptomatic relief from congested chests and coughs which may be due to a cold, bronchitis, and/or other breathing illnesses .

Hydrocodone is an opioid agonist used as an analgesic and antitussive agent.

Hydrocodone is indicated for the management of acute pain, sometimes in combination with acetaminophen or ibuprofen, as well as the symptomatic treatment of the common cold and allergic rhinitis in combination with decongestants, antihistamines, and expectorants.

Extendryl HC is also used to associated treatment for these conditions: Allergic Reaction, Asthma, Asthma, Allergic, Bronchial Asthma, Bronchitis, Bronchospasm, Chronic Bronchitis, Chronic Obstructive Respiratory Diseases, Common Cold, Cough, Cough caused by Common Cold, Coughing caused by Allergies, Coughing caused by Flu caused by Influenza, Drug Allergy, Emphysema, Fever, Flu caused by Influenza, Food Allergy, Headache, House dust allergy, Irritative cough, Laryngitis, Nasal Congestion, Nasal Congestion caused by Common Cold, Phlegm, Pollen Allergy, Productive cough, Rash, Rhinorrhoea, Sneezing, Sore Throat, Tracheitis, Urticaria, Whooping Cough, Acute Rhinitis, Chest congestion, Chills occurring with fever, Dry cough, Excess mucus or phlegm, Mild to moderate pain, Minor aches and pains, Airway secretion clearance therapy, ExpectorantCough, Cough caused by Allergic Rhinitis, Cough caused by Common Cold, Nasal Congestion caused by Allergic Rhinitis, Nasal Congestion caused by Common Cold, Pain, Acute, Pain, Chronic, Rhinitis caused by Common Cold, Severe Pain, Moderate Pain, Upper respiratory symptoms caused by Allergic Rhinitis, Upper respiratory symptoms caused by Common Cold

How Extendryl HC works

Although the exact mechanism of action of guaifenesin may not yet be formally or totally elucidated, it is believed that expectorants like guaifenesin function by increasing mucus secretion . Moreover, it is also further proposed that such expectorants may also act as an irritant to gastric vagal receptors, and recruit efferent parasympathetic reflexes that can elicit glandular exocytosis that is comprised of a less viscous mucus mixture . Subsequently, these actions may provoke coughing that can ultimately flush difficult to access, congealed mucopurulent material from obstructed small airways to facilitate a temporary improvement for the individual .

Consequently, while it is generally proposed that guaifenesin functions as an expectorant by helping to loosen phlegm (mucus) and thin bronchial secretions to rid the bronchial passageways of bothersome mucus and make coughs more productive, there has also been research to suggest that guaifenesin possesses and is capable of demonstrating anticonvulsant and muscle relaxant effects to some degree possibly by acting as an NMDA receptor antagonist .

Hydrocodone binds to the mu opioid receptor (MOR) with the highest affinity followed by the delta opioid receptors (DOR). Hydrocodone's agonist effect at the MOR is considered to contribute the most to its analgesic effects. Both MOR and DOR are Gi/o coupled and and produces its signal through activation of inward rectifier potassium (GIRK) channels, inhibition of voltage gated calcium channel opening, and decreased adenylyl cyclase activity. In the dorsal horn of the spinal cord, activation of pre-synaptic MOR on primary afferents the inhibition of calcium channel opening and increased activity of GIRK channels hyperpolarizes the neuron and prevents release of neurotransmitters. Post-synaptic MOR can also prevent activation of neurons by glutamate through the aforementioned mechanisms.

Hydrocodone can also produce several actions in the brain similarly to other opioids. Activation of MOR in the periaquaductal gray (PAG) inhibits the GABAergic tone on medulo-spinal neurons. This allows these neurons, which project to the dorsal horn of the spinal cord, to suppress pain signalling in secondary afferents by activating inhibitory interneurons. MOR can also inhibit GABAergic neurons in the ventral tegmental area, removing the inhibitory tone on dopaminergic neurons in the nucleus accumbens and contributing to the activation of the brain's reward and addiction pathway. The inhibitory action or MOR likely contributes to respiratory depression, sedation, and suppression of the cough reflex.

Activation of DOR may contribute to analgesia through the above mechanisms but has not been well studied.

Toxicity

The most prevalent signs and symptoms associated with an overdose of guaifenesin have been nausea and vomiting .

Although adequate and well-controlled studies in pregnant women have not been performed, the Collaborative Perinatal Project monitored 197 mother-child pairs exposed to guaifenesin during the first trimester . An increased occurrence of inguinal hernias was found in the neonates . However, congenital defects were not strongly associated with guaifenesin use during pregnancy in 2 large groups of mother-child pairs .

Moreover, guaifenesin is excreted in breast milk in small quantities . Subsequently, caution should be exercised by balancing the potential benefit of treatment against any possible risks .

Additionally, an LD₅₀ value of 1510 mg/kg (rat, oral) has been reported for guaifenesin .

Overdosage with hydrocodone presents as opioid intoxication including respiratory depression, somnolence, coma, skeletal muscle flaccidity, cold and clammy skin, constricted pupils, pulmonary edema, bradycardia, hypotension, partial or complete airway obstruction, atypical snoring, and death.

In case of oversdosage the foremost priority is the maintenance of a patent and protected airway with the provision of assisted ventilation if necessary. Supportive measures such as IV fluids, supplemental oxygen, and vasopressors may be used to manage circulatory shock. Advanced life support may be necessary in the case of cardiac arrest or arrhythmias. Opioid antagonists such as naloxone may be used to reverse the respiratory and circulatory effects of hydrocodone. Emergency monitoring is still required after naloxone administration as the opioid effects may reappear. Additionally, if used in an opioid tolerant patient, naloxone may produce opioid withdrawal symptoms.

Volume of Distribution

The geometric mean apparent volume of distribution of guaifenesin determined in healthy adult subjects is 116L (CV=45.7%) .

The apparent volume of distribution ranges widely in published literature. The official FDA labeling reports a value of 402 L. Pharmacokinetic studies report values from 210-714 L with higher values associated with higher doses or single dose studies and lower values associated with lower doses and multiple dose studies. Hydrocodone has been observed in human breast milk at levels equivalent to 1.6% of the maternal dosage. Only 12 of the 30 women studied had detectable concentrations of hydromorphone at mean levels of 0.3 mcg/kg/day.

Elimination Route

Studies have shown that guaifenesin is well absorbed from and along the gastrointestinal tract after oral administration .

The absolute bioavailability of hydrocodone has not been characterized due to lack of an IV formulation. The liquid formulations of hydrocodone have a Tmax of 0.83-1.33 h. The extended release tablet formulations have a Tmax of 14-16 h. The Cmax remains dose proportional over the range of 2.5-10 mg in liquid formulations and 20-120 mg in extended release formulations. Administration with food increases Cmax by about 27% while Tmax and AUC remain the same. Administration with 40% ethanol has been observed to increase Cmax 2-fold with an approximate 20% increase in AUC with no change in Tmax. 20% alcohol produces no significant effect.

Half Life

The half-life in plasma observed for guaifenesin is approximately one hour .

The half-life of elimination reported for hydrocodone is 7-9 h.

Clearance

The mean clearance recorded for guaifenesin is about 94.8 L/hr (CV=51.4%) .

Official FDA labeling reports an apparent clearance of 83 L/h. Pharmacokinetic studies report values ranging from 24.5-58.8 L/h largely dependent on CYP2D6 metabolizer status.

Elimination Route

After administration, guaifenesin is metabolized and then largely excreted in the urine .

Most hydrocodone appears to be eliminated via a non-renal route as renal clearance is substantially lower than total apparent clearance. Hepatic metabolism may account for a portion of this, however the slight increase in serum concentration and AUC seen in hepatic impairment indicates a different primary route of elimination.

Innovators Monograph

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