**6. Adverse effects of herbal medicines**

An adverse drug reaction is defined as "a harmful or troublesome reaction, due to intervention related to the use of a healing substance, which envisages risk from future administration and requires prevention or explicit treatment, or alteration of dose and method of administration, or withdrawal of the medical substance." Any substance with a healing effect can generate unwanted or adverse side reactions. As with synthetic drugs, the quality, efficacy, and safety of medicinal plants must also be assured. Despite the widespread use of herbal medicines globally and their reported benefits, they are not completely harmless. In as much as medicinal herbs have established therapeutic effects, they may also have the potential to induce adverse effects if used incorrectly or in overdose. The likelihood of adverse effects becomes more apparent due to indiscriminate, irresponsible, or nonregulated use and lack of proper standardization. These concerns have been the focus of many international forums on medicinal plants research and publications [53]. The rich flora of Africa contains numerous toxic plants, though with interesting medicinal uses. The toxic constituents (e.g., neurotoxins, cytotoxins, and metabolic toxins) from these plants can harm the major systems of the human body (cardiovascular system, digestive system, endocrine system, urinary system, immune system, muscular system, nervous system, reproductive system, respiratory system, etc.) [25].

In a survey in Lagos metropolis, Nigeria, among herbal medicine users, it was found that herbal medicine was popular among the respondents but they appeared to be ignorant of its potential toxicities [22]. Several herbal medicines have been reported to have toxic effects. Current mechanisms to track adverse effects of herbal medicines are inadequate [15, 54, 55]. Consumers generally consider herbal medicines as being natural and therefore safe and view them as alternatives to conventional medications. Only very few people who use herbal medicines informed their primary care physicians. It is therefore likely that many adverse drugs reactions go unrecorded with either patients failing to divulge information to health services, and no pharmacovigilance analyses are being carried out, or the observations are not being reported to appropriate quarters such as health regulatory bodies. Establishing a diagnosis of herbal toxicity can be difficult. Even when herbal-related toxicity is suspected, a definitive diagnosis is difficult to establish without proper analysis of the product or plant material. Very few adverse reactions have been reported for herbal medicines, especially when used concurrently with conventional or orthodox medicines [15]. The results of many literature reviews suggest that the reported adverse drug reactions of herbal remedies are often due to a lack of understanding of their preparation and appropriate use.

medicines with some conventional drugs or supplements [11]. Incorrect identification and

Herbal Medicines in African Traditional Medicine http://dx.doi.org/10.5772/intechopen.80348 207

**Figure 5.** Serum enzyme levels in herbal medicine users (test group) and nonusers (control).

It is therefore pertinent at this time to present correct, timely, and integrated communication of emerging data on risk as an essential part of pharmacovigilance, which could actually improve the health and safety of patients. This calls for improved collaboration between traditional practitioners and modern health care professionals, researchers, and drug regulatory authorities. The latency period between the use of a drug and the occurrence of an adverse reaction, if determined, can also help in its causality assessment in pharmacovigilance management [25]. Such information can be invaluable in the interpretation of drug safety signals, and facilitate decisions on further protective actions to be taken concerning future use.

**7. Traditional African medicine and its relationship with modern** 

Plants have been the primary source of most medicines in the world, and they still continue to provide mankind with new remedies. Natural products and their derivatives represent more than 50% of all drugs in clinical use, of which higher plants contribute more than 25%. These

misuse of plants may also lead to toxicity.

**Figure 6.** Effect of length of use of herbal medicine on serum enzyme levels.

**medicine**

In a research of liver and kidney functions in medicinal plant users in South-East Nigeria, it was found that liver problems were the most prominent indices of toxicity as a result of chronic use [56]. **Figures 5** and **6** refer to the effect of consumption of herbal medicines and length of usage respectively, on serum enzymes, as an index of liver function. Toxic components in these herbs such as alkaloids, tannins, oxalates, etc., may likely be responsible for such observed toxicities.

Another important source of toxicity of herbal medicines worth mentioning is microbial contamination due to poor sanitary conditions during preparation [57]. Toxicity may also arise as a result of herb-drug interaction in situations where there is co-administration of herbal

**Figure 5.** Serum enzyme levels in herbal medicine users (test group) and nonusers (control).

**6. Adverse effects of herbal medicines**

206 Herbal Medicine

a lack of understanding of their preparation and appropriate use.

such observed toxicities.

In a research of liver and kidney functions in medicinal plant users in South-East Nigeria, it was found that liver problems were the most prominent indices of toxicity as a result of chronic use [56]. **Figures 5** and **6** refer to the effect of consumption of herbal medicines and length of usage respectively, on serum enzymes, as an index of liver function. Toxic components in these herbs such as alkaloids, tannins, oxalates, etc., may likely be responsible for

Another important source of toxicity of herbal medicines worth mentioning is microbial contamination due to poor sanitary conditions during preparation [57]. Toxicity may also arise as a result of herb-drug interaction in situations where there is co-administration of herbal

An adverse drug reaction is defined as "a harmful or troublesome reaction, due to intervention related to the use of a healing substance, which envisages risk from future administration and requires prevention or explicit treatment, or alteration of dose and method of administration, or withdrawal of the medical substance." Any substance with a healing effect can generate unwanted or adverse side reactions. As with synthetic drugs, the quality, efficacy, and safety of medicinal plants must also be assured. Despite the widespread use of herbal medicines globally and their reported benefits, they are not completely harmless. In as much as medicinal herbs have established therapeutic effects, they may also have the potential to induce adverse effects if used incorrectly or in overdose. The likelihood of adverse effects becomes more apparent due to indiscriminate, irresponsible, or nonregulated use and lack of proper standardization. These concerns have been the focus of many international forums on medicinal plants research and publications [53]. The rich flora of Africa contains numerous toxic plants, though with interesting medicinal uses. The toxic constituents (e.g., neurotoxins, cytotoxins, and metabolic toxins) from these plants can harm the major systems of the human body (cardiovascular system, digestive system, endocrine system, urinary system, immune system, muscular system, nervous system, reproductive system, respiratory system, etc.) [25]. In a survey in Lagos metropolis, Nigeria, among herbal medicine users, it was found that herbal medicine was popular among the respondents but they appeared to be ignorant of its potential toxicities [22]. Several herbal medicines have been reported to have toxic effects. Current mechanisms to track adverse effects of herbal medicines are inadequate [15, 54, 55]. Consumers generally consider herbal medicines as being natural and therefore safe and view them as alternatives to conventional medications. Only very few people who use herbal medicines informed their primary care physicians. It is therefore likely that many adverse drugs reactions go unrecorded with either patients failing to divulge information to health services, and no pharmacovigilance analyses are being carried out, or the observations are not being reported to appropriate quarters such as health regulatory bodies. Establishing a diagnosis of herbal toxicity can be difficult. Even when herbal-related toxicity is suspected, a definitive diagnosis is difficult to establish without proper analysis of the product or plant material. Very few adverse reactions have been reported for herbal medicines, especially when used concurrently with conventional or orthodox medicines [15]. The results of many literature reviews suggest that the reported adverse drug reactions of herbal remedies are often due to

**Figure 6.** Effect of length of use of herbal medicine on serum enzyme levels.

medicines with some conventional drugs or supplements [11]. Incorrect identification and misuse of plants may also lead to toxicity.

It is therefore pertinent at this time to present correct, timely, and integrated communication of emerging data on risk as an essential part of pharmacovigilance, which could actually improve the health and safety of patients. This calls for improved collaboration between traditional practitioners and modern health care professionals, researchers, and drug regulatory authorities. The latency period between the use of a drug and the occurrence of an adverse reaction, if determined, can also help in its causality assessment in pharmacovigilance management [25]. Such information can be invaluable in the interpretation of drug safety signals, and facilitate decisions on further protective actions to be taken concerning future use.
