Pharmacology and Emergency Medicine - Assignment Example

Case Study Question There are various clinical features that warrant the administration of oxygen to Vincent. He has features of cyanosis, unconscious and barely breathing. These clinical features are suggestive of tissue hypoxia and hypoxemia (Jindal, 2008). In addition, the respiratory rate is low at 4 breaths/minute while the pulse rate is also reduced at approximately 34 beats/minute. These clinical features are suggestive of respiratory depression. Oxygen is a component of air that is necessary for all living cells. In humans, biochemical reactions in the cells depend on oxygen. Decreased oxygen supply to the body tissues results in hypoxia and hypoxemia which results in tissue damage. Adequate supply of oxygen to the body tissue is dependent on the optimal functioning of the respiratory system as well as the central nervous system. This includes the respiratory and medullary centre (Jindal, 2008). It is thus important to administer oxygen to Vincent so as to correct the hypoxemia and prevent end organ damage. Administration of oxygen is necessary to correct the PaO2, oxygen delivery and utilization in the tissues. Oxygen therapy is aimed at correcting the hypoxemia by increasing the alveolar tension. This will decrease the work of the myocardium as well as that of breathing. It will also increase the PaO2 thus increase oxygen deliver and saturation in the tissues. Question 2 Currently, Vincent is taking peginterferon alfa-2a and ribavirin. These are used the management of chronic hepatitis C. Hepatitis C virus is transmitted via blood and its products (David and Charles, 2003). Johnny is at risk of contracting the virus from the shared needles while administering heroin. The paramedic and the partner are also at risk of contracting the virus from needle pricks and blood spills which can occur while administering intravenous drugs. It is thus important for the paramedic and the partner to wear glove, glasses and other protective gears. In addition, Vincent and Johnny have been injecting themselves with heroin. Therefore, needles might be lying around. It is also important to educate Johnny about the risk factors on the transmission of Hepatitis C virus. In addition, I would advise Johnny to go to the hospital for testing if he has already been exposed to the virus. Question 3 Alcohol undergoes first pass metabolism in the liver. It is a substrate of CYP2E1 where, depending on the frequency of alcohol intake, it can inhibit or induce this enzyme (David and Charles, 2003). Due to this effect, alcohol can alter the pharmacokinetic and pharmacodynamic of various medications causing various effects in the body. Vincent is on ceftriaxone, a third generation cephalosporin, which in combination with alcohol has disulfiram-like effects. Although these interactions are rare, ceftriaxone contains a methytetrazolethiol side chain which inhibits the conversion of acetaldehyde to acetate. This triggers accumulation of acetaldehyde which is toxic to the body (Noureldin, 2010). In addition, Vincent is taking fluoxetine, olanzapine and diazepam which act on the central nervous system. Alcohol potentiates the actions of these drugs on the central nervous system. This results in prolonged CNS and respiratory depression, altered mental state, impaired psychomotor skills and judgement. On the other hand, Vincent is on treatment using peginterferon alpha 2a and ribavirin (used in the treatment of chronic hepatitis). Alcohol acts by inhibiting the anti-HCV affects of ribavirin and interferon resulting in virus persistence. In addition, alcohol increases the replication rate of hepatitis C virus resulting in increased viral loads (Noureldin, 2010). This predisposes Vincent to treatment failure and hence, liver failure. Currently, Vincent is abusing heroin which is an opioid. Alcohol potentiates the action of opiod on the central nervous system which includes CNS and respiratory depression (Noureldin, 2010). According to Johnny, they have not been able to feed properly despite their activities and current medication. This predisposes Vincent to hypoglycaemia which leads to CNS depression hence, loss of consciousness. The above reasons justify why Vincent is more affected that his friend Johnny. Question 4 Opioid agonists act on three receptor types: mu, delta and kappa (Bolan, Tallarida & Pasternak, 2002). Mu receptors are of importance, pertaining to respiratory depression. Opioid receptors at the molecular level are a protein family that couple to G proteins. Through this interaction, they affect ion channel gating, alter protein phosphorylation and modulate intracellular calcium ions disposition. This leads to decreased release of transmitters such as excitatory neuropeptides and glutamate; therefore, brainstem depression (Bonc & Williams, 1997). Respiratory depression occurs due to mu receptor agonists at the CNS. This leads to inhibition of brainstem respiratory mechanism. Alveolar PCO2 becomes elevated. The respiratory drive is decreased leading to decreased respiratory rate with a decreased tidal volume. The patient also exhibits a decreased response to a CO2 challenge. The respiratory depression is related to the dose of the opiod (Jaffe & Martin, 1990). Question 5 When given intravenously to an opioid overdose case, naloxone dramatically and completely reverses the effects of opioid within three minutes. Naloxone effectively normalizes level of consciousness, respiration, pupil size, bowel activity and pain awareness. Antagonistic actions of this drug exhibit no tolerance (Jaffe & Martin, 1990). Naloxone is a pure opioid antagonist (Jaffe & Martin, 1990). Naloxone has a high affinity for mu opioid binding site. It is a morphine derivative with a substituent at N17 position. Acute opioid (narcotic) overdose is treated with intravenous naloxone. However, naloxone has a short duration of action: 1-2 hours. A patient may recover after a single naloxone dose only to lose consciousness after an hour or two. Henceforth, for full reversal, there is a need for maintenance dose at levels of upto four times the initial dose (Jaffe & Martin, 1990). For partial reversal of narcotic overdose, naloxone is given in smaller doses. Partial reversal is necessary in situations where rapid and complete reversal may trigger vomiting, circulatory stress and sweating. Question 6 It is imperative that Vincent seeks further medical attention. It is worth noting that opioid affects many systems within the body. Apart from CNS depression, opioid abuse causes truncal rigidity, which may interfere with ventilation by decreasing thoracic compliance. Nausea and vomiting may lead to metabolic imbalances by potentiating ion losses. Another action of opiods on the human body is constipation. This can trigger intestinal obstruction and may lead to anal complications such as anal fissures and piles. Opiods also depress renal function. Hormonal imbalances pertaining to Prolactin, Somatotropin and ADH are also side effects of opioid abuse. Immune system alteration is also noted. Therefore, it is necessary to carry out further tests on Vincent so as to rule out the above side effects of opioid abuse (Ferner & Daniels, 2003). Complete blood count is necessary, considering the effect on the immune system. Pulmonary function tests are vital such as flow rate tests. It is also important to assess concentration of essential electrolytes. Renal function tests are also important. Hormonal assessment can also be carried out. 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Noureldin, M 2010, ‘Drug-Alcohol Interactions: A Review of Three Therapeutic Classes’, Journal of US Pharmacist, vol. 35, no. 11, pp. 29-40. Read More