Endoplasmic Reticulum & Drug Metabolism

Each of the cells in your body has a nucleus where genetic matter lives along with various organelles, or working parts of the cell. These organelles, which include the endoplasmic reticulum, carry out specific tasks that contribute to the cell's metabolism. This organelle metabolizes drugs and toxins. The endoplasmic reticulum consists of a network of tubules and vacuoles. You metabolize most drugs in the liver, one of the body's filtering systems. The endoplasmic reticulum in the cells of the liver have the responsibility of filtering out dangerous substances, which then get excreted by the kidneys or the digestive system.

Physiology

The endoplasmic reticulum, or ER, has three regions that have different roles. The smooth endoplasmic reticulum metabolizes drugs and toxins, and also metabolizes carbohydrates and synthesizes cholesterol, carbohydrates and lipids. Within the smooth ER region, the sarcoplasmic reticulum has many calcium pumps and calcium storage areas. It specializes in regulating calcium by pumping it out when signaled, or by storing it. The second ER region, the rough endoplasmic reticulum, controls protein synthesis. The last ER region, the transitional endoplasmic reticulum, takes part in transporting proteins.

Factors Affecting Drug Metabolism

Drug companies assign dosages to medicines based on many variables. These depend on how much medicine the average person actually utilizes in the body. This varies from person to person depending on sex, age, health, smoking and drinking patterns, ethnic background, other medications and food consumption. These variables factor into how much medicine you actually absorb, an amount that isn't always the amount you swallow. Liver disease impairs your ability to metabolize a drug. You might become toxic from absorbing too much medication or absorb too little and not receive the optimum benefit from the drug. Ultimately, the smooth ER becomes incapacitated in liver diseases such as cirrhosis.

Cytochrome P450

Enzymes modulate every physiologic process in the body. Without them, there would be no action. Enzymes often work side by side. In some cases, enzymes conflict with each other. Some want to inhibit metabolism of a drug, while others try to enhance the drug's action. The enzyme cytochrome P450 is one of the major players in drug metabolism. It interacts with the endoplasmic reticulum to enhance the metabolic process. Some drugs have enzymes that inhibit metabolism.

Drug Interactions

When cytochrome P450 comes up against another enzyme that has a conflicting purpose, side effects occur that might not have while using only one drug. The interaction lessens the effectiveness of one or both of them. This can cause a worsening of symptoms, because the opposing enzymes render the smooth ER useless. Alternately, one drug may increase the effectiveness of the other. When this happens, you can overdose. In other cases, the use of two drugs that use opposing enzymes pathways for metabolism may cause serious side effects such as heart irregularities or stroke. Another side-effect occurs in the liver itself. The smooth endoplasmic reticulum becomes enlarged, which eventually enlarges the liver. This compromises the liver's ability to metabolize medications.

Cytochrome P450 Antagonists

Drugs that inhibit by virtue of their enzymatic actions include amiodarone, cimetidine, ciprofloxacin, fluvoxamine, fluconazole, metronidazole, ritonavir, Bactrim, fluvoxamine, isoniazid, cimetidine, Benadryl, Prozac, Paxil, quinidine and Lamisil. Drugs that enhance metabolism such as cytochrome P450 include carbamazepine, phenobarbital, tobacco and phenytoin. You should check with your physician or pharmacist before adding a drug to your regimen.